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United States Department of Agriculture

Agricultural Research Service

LAJPAT R. AHUJA (LAJ)

Research Leader

Dr. Lajpat Ahuja

FACTOR 1. Research Assignment

 

A. Assigned Responsibility

The incumbent is a Supervisory Soil Scientist and Research Leader of the Agricultural Systems Research (ASR) Unit, Fort Collins, Colorado, responsible for developing and directing a nationally critical systems R&D program with five related outcomes: (1) synthesis and quantification of disciplinary knowledge to the whole system level; (2) process-level models of agricultural systems for evaluation of management and climate effects on sustainability of production and the environment; (3) applications of models to enhance and extend field research and fill knowledge gaps; (4) simpler decision-support technology for farm advisors, producers, and action agencies to guide management; and (5) an Object Modeling System (OMS) framework to streamline the creation and update of future ARS models and technology tools from a library of modules, and their deployment by the Natural Resources Conservation Service (NRCS) and other users. These systems-based approaches are needed to address many new research frontiers in food, health, environments, and communities (NAS Report: Frontiers in Agricultural Research, 2002). Incumbent provides technical leadership, direction and challenge

for research in the program; articulates a vision of the future; promotes focused team efforts; and establishes external cooperative relationships with other ARS units, NRCS and other federal agencies, universities, industry (CRADAs), and internationally. As an internationally recognized scientific leader in above areas, assists and mentors other scientists in their research activities. Responsible for optimal management of Unit's human, fiscal, and physical resources. Primary

National Programs for this research are 211 and 216.

 

B. Research Objectives and Methodology

 

Incumbent’s focus for the next 5 years is to collaborate with field researchers in using system models to: (1) enhance understanding of complex interactions in field results and extend them to multiple years of weather and other soils, climates, and management practices in limited water systems; (2) improve quantification of water stress effects on plant growth and yield; (3) evaluate the effects of projected climate change on crop water demand, soil water availability, and crop production, and explore potential adaptations to climate change; and (4) define how spatial variations of soils, climate, and cultivars and root systems influence the response of crops to water. Currently, the Unit has two research projects to address these objectives: (1) Enhanced System Models and Decision Support Tools to Optimize Water Limited Agriculture; and (2) Object Modeling and Scaling of Landscape Processes and Conservation Effects in Agricultural Systems. In addition, the Unit continues to lead further enhancement and deployment of OMS in partnership with NRCS, Colorado State University, and international collaborators. Incumbent contributes to these projects by way of: overall leadership and coordination, contributions to science, and collaborative research.

 

C. Expected Results

 

Incumbent’s Unit leadership and national efforts are achieving major ARS objectives  by providing synthesis of knowledge across disciplines to whole systems level and computer models of systems that: (1) help evaluate and enhance economic and environmental sustainability of current agricultural systems; (2) meet customer and action-agency needs for analysis of critical water, water quality, and climate change problems; (3) enhance efficiency and economy of field research and technology transfer; and (4) provide an Object Modeling System that will coordinate all future model development and technology tools in ARS and their deployment by NRCS. Successful completion of the incumbent's research will also provide: (1) an enhanced understanding and theory to quantify the effects of management practices, water stress, and cropping patterns on water storage, water quality, and crop production; (2) effects of projected climate change and potential adaptations; (3) spatial relationships among soil, landscape, management, weather, and yield variability to serve as sound basis and decision aids for precision farming and scaling. This research is on the forefront of science that will inspire studies and advancements in fields beyond crop-environment systems, such as modeling of weeds, insects, and diseases.

 

D. Knowledge Required


The research assignment requires expert knowledge of advanced soil physics, chemistry, plant physiology, mathematical techniques, geostatistics, system modeling, and systems analysis. It also requires a high level of outside-the-box thinking and creativity, experience, and skills in understanding environmental variables and crop growth; developing unique and far-reaching concepts and theories across disciplines; extending models to complex situations; and analyzing and interpreting results. Incumbent must also possess leadership, time management, team building, and team direction skills.

 

E. Supervisory Responsibilities

Supervises research of the entire Unit, having 5 Cat.1 SYs; 1 Cat. 4 SY; 13 support persons; 3 post-doctoral SCA employees, and 3 students. Provides direct technical and administrative supervision to 2 GS-15+2 GS-14 Cat. 1; 1 GS-13 Cat. 4; 1 GS-11 Cat. 3; and 1 GS-7 Cat. 9 employees, and directs the work of 3 post-doctoral cooperative scientists. Is responsible for making selections for positions, assigning duties, reviewing work, approving/disapproving leave, and evaluating performance. Ensures equal opportunity is extended to all employees supervised and all candidates for employment without regard to race, color, religion, sex, national origin, age, or nondisqualifying handicapping condition. Ensures affirmative implementation of Equal Employment Opportunity plans of action and applicable Civil Rights provisions which includes full consideration of eligible minority group members and women in filling vacant positions; providing career counseling and orientation; enhancing career opportunities through training and development, job redesign, and/or similar techniques; and ensuring full consideration of these employees in recommending promotions, awards, and other forms of special recognition.

 

FACTOR 2. Supervisory Controls

A. Assigned Authority

 

Has complete responsibility and freedom in selecting the most critical knowledge gap areas and problems to be researched by the team, as well as consultative role on the approaches and methods. Makes these complex choices based on the identified customer needs, identified shortcomings in the Unit's products, practical and scientific values of the outcomes, and scientific soundness.

 

B. Technical Guidance Received

 

Is a recognized scientific leader and national/international authority in the field, needing no technical supervision.

C. Review of Results


Has full responsibility and complete freedom in analyzing, interpreting, and reporting results, including their applicability to science, ARS mission, and mission of NRCS, EPA or other agencies. Manuscripts are peer reviewed, but accepted as technically correct and authoritative. Along with other similar work they serve as a basis for ARS and interagency actions.

D. General Supervision


Meets with the Area Director as needed for consultation on personnel matters and new ideas for the program. Incumbent’s recommendations for changes in program and resource allocation are normally accepted without alteration.

FACTOR 3. Guidelines and Originality


A. Available Literature


The RL position for systems research requires highly exceptional personal, scientific and professional leadership characteristics, for which the literature provides no guidance. The literature contains a preponderance of site-specific qualitative information on how management and environment affect soil, water, water quality, and crop growth processes; however, this information is piecemeal and not integrated in terms of process-based parameters for general application; system models are needed to do this. For spatial and temporal variabilities, the work

over the last four decades on geostatistics has failed to provide cause-effect relations; physicalconceptual methods are needed to quantify the variability and scale results from plots to fields and farm, and to aid precision farming. A refinement of cropping system models under water stress is on the forefront of knowledge, with no guidance available.

B. Originality Required


A high degree of originality and creativity is required in: (1) developing and directing a nationally critical, state-of-the-science, systems R&D program; (2) extending fundamental principles to understanding of complex changes caused by management practices and the highly complex soil-landscape-management-weather-crop variability and interactions, (3) developing new concepts, models, and methods of quantifying these effects; and (4) finding ways to make system models a reliable tool for helping sustain agriculture and environment in the 21st Century, and raise agricultural research and technology transfer to the next level.

 

C. Demonstrated Originality

Incumbent’s research is highly original and unique, driven by a passion to solve problems, and marked by innovation, analytical thinking, and thoroughness. Dr. Ahuja’s research in soil physics has extended to synthesis and modeling of whole systems, crops, range, weeds and even insects, resulting in two system level models, RZWQM, GPFARM/GPFARM-Range. His pioneering original research that went into the models included: (1) a new theory of chemical transfer from soil surface and subsurface pathways to runoff; (2) quantification of management effects on soil properties and soil-water processes, especially of tillage or no-tillage and residue cover, macropores (root channels, worm holes), surface aggregation, and crop row-interrow effects; (3) new infiltration models and new simpler methods to determine soil hydrologic parameters; (4) state-of-the-science pesticide dynamics and transport in soil and macropores to tile drains and groundwater; and (5) modeling spatial variability and scaling across soil types. His original contributions to inter-disciplinary research areas include: (6) modeling root growth

as function of soil density, water, and temperature; (7) uptake of water and nutrients; (8) water stress effects on plant growth and different irrigation levels on yield; (9) energy balance of plant canopies, evapo-transpiration (ET), and canopy temperature; (10) effect of residue cover on soil temperature and ET; (11) effect of crop rotations, cover crops, and initial soil water on crop water use, yield, and soil C; (12) modeling effect of manures, fertilizer and water application methods (e.g., banding, furrows), and controlled drainage on yield and N leaching; (13) modeling crop growth of canola and other new crops; (14) modeling grazing intensities on forage production and animal weight gain; and (15) climate change effects on crop water use, and production. Led a successful partnership with NRCS and USGS to develop the Object Modeling System (OMS) as a uniform system to streamline the creation and delivery of customized models and decision support tools from a library of modules.

FACTOR 4. Contributions, Impact, and Stature


Incumbent’s contributions include 200+ journal papers and 33 book chapters. His post-Ph.D. papers have been cited 3200 times, with 16 citations per paper. Developed/edited seven books and two Special Issues of Geoderma journal on synthesis of knowledge and system modeling. To promote trans-disciplinary research for knowledge-gaps and to promote the application of system models in research, incumbent organized several national/intern. symposia /workshops, gave 5+ invited keynote/lead talks, started a new series on Advances in Ag System Modeling, and developed national/intern. collaborations. Has worked with, helped, and mentored 20+ national/intern. visiting scientists, 18 post-doctorals, 14+ ARS colleagues, and 12 graduate students, who wanted to work with him. Served on Steering Committees for ARS National Program customer workshops and Action Plans; Co-Team Leader for ARS models and databases and multi-location national projects. RZWQM model used worldwide by scientists, federal and state agencies, and private sector for water/water quality management evaluation and pesticide registration and regulation, with 230+ publications. NRCS has adopted and is investing heavily in OMS to streamline the development and delivery of conservation models & tools, and manage data & programs; other federal agencies, universities, and private sector have started or requesting to use it. ASR Unit attracted $2+ million from other federal agencies. Incumbent received major national/ international awards; elected to leadership positions in Societies. Has influenced the direction of ARS systems modeling and applications research.

 

A. Demonstrated Accomplishments:


*1. Accomplishment/Role - New Theory of Chemical Transfer from Soil to Runoff:
Established the nature of rainfall-soil interaction as raindrop-impact induced turbulent diffusion process by showing, contrary to the prevalent view of a uniform mixing, that degree of rainfall-soil mixing decreases with depth, while a surface layer of clods increases mixing. Developed and validated an accelerated diffusion model and a simple non-uniform mixing model. Theoretical analyses and experiments revealed and quantified source areas and pathways of subsurface interflow of chemicals to runoff in sloping layered soils. Developed equations of an original model for kinetic release of P from soil to runoff and determined rainfall and slope factors in the model. Role: Incumbent was primary contributor to theory and models, but validations were done with colleagues. Impact: This seminal work for a major water quality problem inspired further studies in ARS and elsewhere (Univ. of Kansas, J. Environ. Engineering, ASCE, 113:49, 1987; ARS-Riverside, CA, Soil Sci. Soc. Am. J. 52:612-618, 1988; Water Resources Res. 26:2119-2126, 1990). The non-uniform mixing concept is used in the ARS Root Zone Water Quality Model (RZWQM) and by private consultants (Waterborne Environment, Inc.) and officially adopted by US-EPA in their PRZM-3 model for use by the pesticide industry to determine potential risk of new pesticides in runoff for the EPA registration. California Dep. Pesticides Regulation (EPR) is using RZWQM to assess pesticides in runoff from orchards and vegetable crops and has provided $140K to include erosion in it. (Exh.1a, #61; Exh. 1b, EPA+ EPR letters; #39, #49, #24, #25, #27, #28, #29, #30, #31, #35, #37, #40, #41, #47, #48, #50).

 

*2. Accomplishment/Role - The State-of-the-Science Agricultural System Model RZWQM: Incumbent as RL since 1991 led the development of the ARS RZWQM Model and contributed key original or improved components and synthesis across components (see 4D-3a,b). Unique features of RZWQM include incumbent’s pioneering quantifications of tillage effects, soil-water dynamics, faster transport of surface-applied chemicals through macropores in no-till soils to tile flow and groundwater, and other management effects. Collaboratively tested and refined several components and the model as a whole, on data from United States and abroad; added DSSAT crop growth, SHAW residue-effect and energy balance/canopy temperature components, and new crops (4D-3a,b). As a result, RZWQM allows unique state-of-the-science evaluations of cropping systems and management (4D-3b). Impact: RZWQM has been used extensively to evaluate and minimize water quality impacts ( N and pesticide losses) in different agricultural systems in the United States, Canada, Portugal, China, UK, and other countries (40 groups worldwide), with 1300+ downloads and 220+ publications (see website below). Incumbent has trained 25+ groups in using model. RZWQM was selected for water quality evaluations of Midwest agricultural systems in the MSEA and follow-up projects (17 papers in Agronomy J. 91: 169-227, 1999, and Geodema 140, 2007). The Chinese showed 30-50% reduction in N losses by RZWQM-suggested management (#180). Scientists in Iowa have used RZWQM to evaluate regional impact of controlled tile drainage and cover crops on N losses in Midwest. USGS is using it for National Water Quality Assessment (NAWQA) U.S. wide. Received two national Technology Transfer awards for RZWQM (4 B-1). Invited RZWQM/management consultant to China, FAO (India, Egypt), Swiss IT, Portugal, and CIMMYT (4B2,C1). (Exh. 2a, #280; Exh. 2b, Iowa+ USGS letters; also see Exh.1b, and #89, #77, #81, #84, #91, #94-96, #99, #104, #125, #134, #136, #143, #149, #150, #153, #172, #180, #183, #198,#199, 200, 202). RZWQM pubs+download model: http://www.ars.usda.gov/Main/docs.htm?docid=17740

 

*3. Accomplishment – A Whole Farm/Ranch Decision Support System (DSS) GPFARM and the GPFARM-Range-Livestock Model: ASR Unit led by incumbent developed the GPFARM (Great Plains Framework for Agricultural Resource Management) DSS, for use by farm/ranch advisors and advanced farmers/ ranchers in strategic planning, evaluating long-term management effects on production, economics, and environmental impacts. GPFARM is the only DSS of its kind that addresses integrated farm and ranch management. A major outcome of this is the standalone GPFARM-Range-livestock model to extend range research and develop management guides. Role: Incumbent provided leadership for the project, and contributed several key components. Took leadership in testing GPFARM and advancing the use of GPFARM-Range for evaluating grazing systems. (see details in 4D-3c) Impact: GPFARM has been adopted by Colorado Assoc. of Wheat Growers and distributed to over 600 members, with an MOU for training by ASRU; also provided to many other farmers. Unit received “Outstanding Laboratory Award” from Federal Lab. Consortium for Technology Transfer of GPFARM (2004), and GPFARM appeared in popular press articles (4D-3h). GPFARM-Range model has been used to synthesize experimental data on grazing intensities at ARS stations in

Cheyenne, WY, Miles City, MT, and Woodward, OK and to extend results to multiple years of weather. A simple tool was developed for the Cheyenne range conditions to predict forage level in the coming season based on soil moisture in early April and approximate forecast of April-May rainfall, to adjust stocking rate in the coming season. With an $800,000+ grant from USDA-RMA (4D-3j), the Unit developed a rangelands drought management tool in Western United States with help of the GPFARM-Range model (Exh. 3a, #156; Exh. 3b, #162; #127, #146, #193, 201). Download GPFARM at: http://www.ars.usda.gov/npa/ftcollins/gpsr/gpfarm.

*4. Accomplishment - Estimating Soil Model Parameters from Simpler Data: For wider application of models to enhance field research and management, it is essential that the soil parameters be obtainable from easily measured soil properties. Incumbent discovered a general saturated conductivity (Ksat) - effective porosity relation and developed two 1-parameter scaling methods that allow estimation of Ksat and water retention of soils and their spatial variability from soil bulk density and 1/3-bar water content. The methods were tested and validated against a dozen soils and enhanced. Recently Dr. Ahuja has created methodology to obtain effective average properties of a heterogeneous field. He co-created an ASA-SSSA-CSSA book on easy parameterization of models, entitled “Methods of Introducing System Models into Agricultural Research” (#340). Role: Lead role in above developments, even though work was done cooperatively with colleagues. Impact: The simple estimations of parameters are incorporated into RZWQM and GPFARM and have made the models much easier to use by field researchers. Work benefited research of several colleagues and published as invited chapters in two ASA monographs. Ksat work was followed up by Swedish and U.S. scientists (Soil Sci. Soc. Am. J. 53:665, 55:1801; 63: 1086; Trans. ASAE 44:235). Dr. Ahuja served as a consultant to NRCS on these techniques to generate soil-water properties of all soil series and horizons for their RVLAYER and National Soil Information System (NASIS) database, distributed to all NRCS State Offices and used in 2540 NRCS field offices as inputs to decision tools for water quality. NASA has used this research to determine spatial hydraulic properties on a large watershed from remotely sensed soil moisture (#97, #98). Invited Keynote speaker at U.S.-German Soil Sci. Soc. Mtg. 2000. Invited member of ASABE committee to standardize model parameterizations, 2011- 2012 (4B-3m). (Exh. 4a, #269, Exh. 4b, NRCS Letter; #42, #43, #46, #62, #66, #67, #68, #108, #129, #133, #191).

 

*5. Accomplishment – Pesticide Movement to Tile Flow and Groundwater: Incumbent developed a soil pesticide transport module that included 2-site equilibrium-kinetics sorption, neutral or ionic pesticides, and rapid transport from surface to tile flow or groundwater thru macropores (MP). Led and guided field testing and refinement of the module on U.S. and international data. The MP flow component was enhanced to include the concepts of ‘effective macroporosity,’ as not all MPs were found to be active and their activity depended upon soil moisture and rainfall rate. Devised a method to measure effective MPs and established that a few MPs may be connected directly to tile drains, affecting peak pesticide concentration in tiles. Improved pesticide module successfully simulated management effects on pesticides in tile flow at Walnut Creek watershed, Iowa. Role: Incumbent led module development/refinement, guided support and postdoc scientists, and mentored younger colleagues (L. Ma, R. Malone) in testing. Impact: George Sabbagh, Bayer CropScience, used results of the pesticide module in RZWQM to register Isoxaflutole with USEPA and to assess the environmental impact of pesticide treated seeds as requested by USEPA. This saved the company 2-3 million dollars and 2-3 years in time. Tom Nolan, Jack Barbash, and Frank Voss in USGS used it to simulate pesticide fates for their NAWQA project. Incumbent invited by the California Dep. of Pesticide Regulation (DPR) and conducted a week-long training on pesticide simulations. On advice of the Scientific Advisory Panel, the USEPA used RZWQM in carbamate subsurface assessment in 2005. The University of Manitoba used RZWQM for estimating potential pesticide contamination in groundwater for all the soils and climates in Canada. Set of 6 invited papers on RZWQM use were printed in Pest Management Science 60: 205-285 (#138-142, #144). (Exh. 5a, # 79; Exh. 5b, Letter-Sabbagh; also see Exh.1b, 2b; and #69, #73, #75, #76, #78, #79, #82, #86, #93, #116, #131, #135).

*6. Accomplishment – Models to Help Manage Limited Water and Climate Change: Incumbent is leading the Unit’s efforts to use RZWQM to help optimize the use of limited water in dryland and irrigated crop systems in the Great Plains and irrigated wheat-corn double cropping systems in China. He guided studies that explored the effects of no-tillage, crop rotations, planting dates, irrigation scheduling, water allocation between crops, and selection of a right summer crop. Results were extended to long-term weather data risk and economic analysis and evaluate effects of climate change. The studies led to proposed summer crop selection based on soil water at planting in dryland wheat rotations, best irrigation strategies based on crop growth stage and soil water depletion, corn yield vs. water functions to guide limited irrigation, and projected climate change effects on water, dryland crop production and potential adaptations. Role: Incumbent conceived, planned, and guided Unit’s collaborative research with the ARS stations and China, and co-directed a CSU cooperator and 6 visiting scientists from China and India. Impact: Modeling enhanced ARS-Akron research; David Nielsen is using RZWQM for regional evaluation of diversified dry-land cropping systems, with canola, millet, corn or forages in rotations, and to create decision tools for farmers to make sustainable choices. Incumbent was invited to Chinese Academy of Science and China Agricultural University 2 times to guide RZWQM applications in water and N management (4C1). Model results guide China farmers to allocate limited water to 2 critical wheat growth stages (stem elongation and booting), with no or one irrigation at corn planting in rotation, saving 30-50% water. A CRADA with Regenesis Group funds incumbent ($62K/year) for water production functions for different crops using RZWQM and long-term weather data. Adaptive Resources, Inc., CO, is using RZWQM for consulting on water issues. (Exh. 6a, #178; Exh. 6b, Nielsen+Yu letters; and #122, #130, #150, #151, #180, #185, #190, # 192, #196, # 197, #202, # 300).

 

*7. Accomplishment/Role- The Object Modeling System (OMS): Incumbent provided vision and leadership, and secured funds and personnel, in developing OMS framework, in partnership with NRCS, USGS, and CSU, to build modular system models at field to watershed scales from a library of science and auxiliary modules (4D-3d). OMS is a uniform system that consolidates and streamlines the creation of worldwide models, parameterization, sensitivity/statistical analyses, and visualization, and their deployment by NRCS and other users. OMS models are easier to develop, update and transfer to next generation, use best science for components, are customizable for a region, problem, and data available, and reduce development costs 40-50%. Impact: ARS officially transferred OMS to NRCS in 2008. NRCS has adopted OMS as a uniform system to streamline the building and delivery of all their conservation plan and design tools, for a high-priority Conservation Delivery Streamlining Initiative (CDSI); a prototype cloud implementation of OMS being used by Keystone Alliance for Sustainable Ag. to deliver RUSLE2 technology to ag. producers; has built a PRMS-Water Supply Forecasting tool (a similar OMS model is used in an IAEA project for forecasting flows in the Nile River basin). ASR Unit has built a watershed model, AgES, for NRCS Conservation Effects Assessment, GPFARM-Range, and modules for ARS combined water-wind erosion in OMS. An Expert Panel review of ASR in Jan. 2011 stated: “The OMS is potentially a very important product of the unit-- We strongly recommend a serious level of commitment to this effort”. Friederich-Schiller University, Germany, and Trento University, Italy, have adopted OMS. Colorado State University (CSU) has established a new OMS Lab to support new OMS users: the DSSAT crop modeling group, USACOE, EPA,+ to maintain and enhance their modeling packages (Exh. 7a, #145; Exh. 7b, NRCS+CSU letters; #194, # 203; #302, #335, # 329, #336).

*8. Accomplishment – Leadership on the Frontiers of Science and Technology/Role: As RL since 1991, Dr. Ahuja has developed a strong system program aimed at five related product goals (1-A). Unit has developed and delivered three high-impact products already presented (RZWQM, GPFARM, OMS). He is now providing passionate leadership to integrate models with field research to enhance sustainability of limited-water agriculture. In support of the program, he organized several national/intern. symposia and workshops; created and edited books and special journal issues to promote research on knowledge gaps (4B2,4), and developed research collaboration with CSU, other universities, and institutions in Portugal, Canada, China, India, Australia, Germany, UK, and France. Impact: Unit’s system models and OMS advance agricultural science and technology needed for the 21st century. Attracted/ recruited, mentored and worked with 20+ visiting scientists ,14+ ARS colleagues, 18 postdocs (5 Headquarters funded), and 12 graduate students (4C-1r,s, 4D-3e,f). Has impacted policy and funding decisions, resulting in in-kind and financial support of NRCS, RMA, USGS, and industry (4D3j). Invited keynote/lead speaker on models and climate change at 5+ international meetings and received many international invitations for collaborations (4B2). Dr. Ahuja’s leadership has been recognized by his leadership positions in Societies (4B3, 4C1): ASA Community Leader for Model Applications in Field Research; invited Series Editor of a new ASA-SSSA-CSSA book series on ‘Advances in Agricultural Systems Modeling”, and Committee Chair for e-publication of modules and datasets. On NPL request, organized ARS science workshops, chaired planning committee for NP207, served on Steering Committees for NP201, NP204, CEAP and ARS Software Policy, and as Co-leader for ARS models and databases and multi-location projects (4C1). ASR Unit is one of the most productive Units in NPA. (Exh. 8a, # 159;  Exh. 8b, AD, NPS, Timlin Letters; #280, #298, #328, #330, #340, #113, #125, #170, 175, 195, 204).

 

Additional Accomplishments:

9. Accomplishment–Extension of Theory and New Models of Infiltration in Crusted Soils: Surface crusting of soils is a worldwide problem that curtails infiltration of rainfall into soils. The incumbent used innovative approaches to investigate detailed physics of this process. A new mathematical transformation and a dimensional similarity were discovered, which generalized the Richards Equation for infiltration into a soil for variable crusts, and which also gave a simple power-form model for describing cumulative infiltration, wetting depth, and suction below the crust. Later, developed new Green-Ampt type models for estimating infiltration into crusted and transient-seal soils. Role: Incumbent independently explored these approaches and developed them further later. Impact: Discoveries expanded the quantitative theory of water movement in crusted soils and its applicability to a wider range of conditions, and provided simpler means to estimate infiltration and runoff. Showing that a simple Green-Ampt type model is physically based and can be applied to unsaturated infiltration into crusted soils was a major breakthrough to existing concepts, as the original Green-Ampt model was thought to be only for ponded-water infiltration into uncrusted soils. New findings have been used in further studies by Australians (Soil Sci. Soc. Am. J. 43:659, 1979, 46:476, 1982), and other research efforts. This basic work led to a similarity model of rain infiltration and three new soil-core methods to determine unsaturated conductivity (#12, #13, #15, #16). Incumbent was invited speaker and author on the subject at an international symposium (#64). The new Green-Ampt model has been used in the ARS Root Zone Water Quality Model (RZWQM). (#9; #36; #10, #11, #13, #18, #64, #215).

10. Accomplishment - New Methods to Measure Hydrologic Characteristics of Watershed Soils and Relate (Scale) These Across Soil Types: Developed an infiltrometer to measure saturated-unsaturated conductivities of all horizons, and discovered 3 new simple methods to determine hydraulic properties of soil cores and 3 new simplified field methods, including a functional approximation that determines both water retention and conductivity functions of all soil horizons from tensiometer data and one water profile measurement. Improved a surface gamma-neutron gauge to quickly measure bulk density, field capacity, and macroporosity of topsoil at numerous locations, as changed by management, in-situ. Recently, developed theory of scaling hydraulic properties, infiltration, and soil moisture across 11 soil series from sandy to clay, based on only the slope of water retention curve or Ksat parameter, and a method to estimate effective properties for a heterogeneous field. Role: Led the studies working with cooperators. Impact: Australians and Dutch followed an idea of this work to propose a new simple method (#38). Research impacted work of other scientists (Soil Sci. Soc. Am. J.48:730, 1984), and ND State Water Commission used one method for turbid water recharge facilities (W. Schuh, J. Hydrology 101: 173, 1988). Above methods appear in two invited chapters of Am. Soc. Agronomy Monograph. 9, Methods of soil analysis, 1986. ARS delegate to IAEA Conference on radiation techniques, France 1983. IAEA-Scholar (Rousseva) to incumbent’s Lab.for a year. IAEA expert to S. Korea. “A scientifically robust scaling framework is the greatest need for making breakthroughs in transferring research knowledge across scales, and to

understand and manage large areas (National Research Council, 1991: opportunities in Hydrologic Sciences)”. (#15, #23, #12, #16, #17, #18, #19, #20, #22, #26, #32, #33, #34, #38, #43, #45, #46, #52, #53, #54, #55, #57, #60, #62, #147, #148, #170, #174).

 

 

B. Stature and Recognition

1. Honors and Awards:


a.
Rockefeller Foundation Fellowship award for graduate study, 1963-64.

b. Govt. of India scholarship award for graduate study in United States, 1965-68.

c. Invited special lecture and award on the “Transfer of applied chemicals to runoff” by Korean Society of Soil Science, 1983.

d. USDA-ARS fellowship for research and study at Princeton University, 1985-86.

e. Scientist of the Year Award, USDA-ARS, Southern Plains Area, 1989. Research award $15,000.

f. Elected Fellow, Soil Science Society of America (SSSA), 1994

g. Elected Fellow, American Society of Agronomy (ASA), 1995

h. Outstanding Scientist of the Year, Association of Agricultural Scientists of Indian Origin, 2002. For excellence in research contributions to science.

i. Environmental and Water resources Institute (EWRI) 2004 Best Paper Award for coauthored paper “Hydrologic response of grasslands: effects of grazing, interactive infiltration, and scale”. J. Hydrologic Engineers. (2002).

j. Senior Scientist of the Year Award, USDA-ARS, Northern Plains Area, 2003. Research award $15,000.

k. Team Award for models: The team led by Dr. Ahuja received the “Outstanding Laboratory Award” from the Federal Laboratory Consortium, Mid-Continent Region, for technology transfer of models-GPFARM for evaluating/managing sustainability of agricultural systems. 2004.

l. Don and Betty Kirkham Soil Physics Award, Soil Science Society of America. 2004. For outstanding contributions in the areas of soil physics; originality and significance of research.

m. Environmental Quality Research Award, American Society of Agronomy, 2006. For creativity, originality, and significance of research for environmental quality.

n. RZWQM Team Award: The team led by Dr. Ahuja received the USDA-ARS Superior Efforts in Technology Transfer for application of RZWQM system model to evaluate/manage water and water quality in agricultural systems. 2006.

o. Elected Fellow, American Association for Advancement of Sciences (AAAS), 2007.

p. RZWQM Team Award: The team led by Dr. Ahuja received the Federal Laboratory Consortium “Excellence in Technology Transfer” for application of RZWQM system model to evaluate/manage water and water quality in agricultural systems. 2007.

q. Soil Science Research Award, Soil Science Society of America, 2010. For outstanding research contributions in soil science; unusual creativity, excellence in reasoning ability, originality and significance of research to basic soil science.

r. Elected Community Leader for “Model applications in field research’ community. American Society of Agronomy. 2011-12. See Society website for the new community structure. Basically, a group of members devoted to an area of research and applications, in this case promoting the use of models in field research.

s. Western Association of Agricultural Experiment Station Directors, Award of Excellence, W-2188 Technical Committee “Characterizing Mass and Energy Transport at Different Vadose Zone Scales” (team award), 2011.

 

2. Special Invitations

 

Have received 60+ special invitations, of which the following are the most significant:

a. Invited by International Atomic Energy Agency (IAEA), Vienna, April 1981, to accept a field mission to Sri Lanka, as an expert to "Assist the local staff in initiating sound, applied research to determine irrigation requirements of various crops and soils of Sri Lanka and to develop improved water management practices...train local staff in effective use of neutron moisture probe..." The IAEA invited the incumbent for a similar mission to South Korea, 1982. See more under Professional and Consulting Activities, 4C1.

 

b. Invited to write a chapter on "Characterization and Modeling of Chemical Transfer to Runoff" for Advances in Soil Science (B.A. Stewart, Editor). 1984. (#49).

 

c. Invited to write a chapter on "Field Soil-Water Relations" for American Society of

Agronomy Monograph, Irrigation of Agricultural Crops, (B.A. Stewart and D.R. Nielsen, co-editors). 1990. (#231). Invited chapter entitled "Determining soil hydraulic properties and their field variability from simpler measurements." Am. Soc. Agronomy Monograph. "Agricultural Drainage." 1994. Published 1999 (#269).

 

d. Invited to give lectures and hold a workshop on the Root Zone Water Quality Model at the University of Guelph, Canada, and develop research collaborations. Oct. 10-17, 1990.


e. Invited to participate in the 1st Inter-Regional Conference on Environment-Water, Intern. Comm. Irrig. Drainage, Lisbon, Portugal, Sept. 15-18, 1998. Presented the lead/keynote paper of the Conference, Applications of the Root Zone Water Quality Model in environment-water management in agricultural systems (#263). Advised on the use of the model and explored research collaboration.

f. Presented an invited lecture on Unit’s program and Root Zone Water Quality and explored research collaboration at the Swiss Federal Institute for Environmental Science and Technology (EAWAG) Zurich, Switzerland, Sept. 9-11, 1998.

 

g. Invited speaker for the Am. Chem. Soc. Annual Meeting Symp. on “The role of simulation modeling in ground and surface-water assessment of pesticides.” Anaheim, CA, March 21-24, 1999. Paper presented: “Role of macropore flow and kinetics on the transport of pesticides of macropores and kinetics on pesticide transport.”

h. Invited (and fully supported) external examiner for Ph.D. thesis defense of a student in Lisbon Technical University, Portugal, April 2000, and to develop research collaboration.

i. Invited by the Soil Sci. Soc. Am. (SSSA) to be a keynote speaker at the First Joint

Congress of the SSSA-German Soil Sci. Soc. on the theme ‘Role of Soils in

Agroecosystems’, September 18-22, 2000. Delivered a talk on “Topographic analysis, scaling, and models to evaluate spatial/temporal variability”. Developed research collaborations with Germans at the Institute of Landscape Systems Analyses, Muencheberg.

j. Delivered an invited lead/opening talk on “Agricultural System Models in Field Research and Technology Transfer” at the 2nd International Agronomy Congress, November 26-30, 2002, New Delhi, India. (#296). Discussed collaborations with scientists at the Indian Agricultural Research Institute, New Delhi.

k. Invited by Lewis publishers/CRC Press as the lead creator and editor of a book on “Agricultural System Models in Field Research and Technology Transfer”, 2002. (#298).

l. Invited by Elsevier Publishers to be Guest Editor for creating and editing a Special Issue of Geoderma on “Quantifying Agricultural Management Effects on Soil Properties and Processes”, 2003. (#125); and another Special Issue on “Integrating Soil and Crop Research with System Models in the Midwest, USA’, 2007 (#170).


m. Invited papers in Special Anniversary Issues of Transactions of ASABE, Agronomy J., and Soil Sci. Soc. Journal, and Trans. ASABE special collection of papers on calibration and validation of water quality models. 2007-2010.

 

n. Invited by CIMMYT, Mexico to present a lead/opening presentation on “Water

Balance—The Influence of a Residue Layer and Tillage on Infiltration, Water Holding

Capacity, and Evaporation” at the International Workshop on Modeling effects of Residue and Tillage. December 8-11, 2003. Also presented a paper on “Current State of Modeling Tillage, No-Tillage, and Residue Cover Effects on Soil water and Temperature in RZWQM”. Discussed collaborations with CIMMYT in above areas.

 

o. Invited by Soil Sci. Soc. Am. Journal, Division S-1 to write a review paper on “Trans-Disciplinary Soil Physics Research Critical to Synthesis and Modeling of Agricultural Systems.” Jan. 2003. (#159).

 

p. Invited (fully supported) by Lawrence Livermore National Laboratory, Livermore, CA, to present our agricultural system models and to explore collaboration in using these models to assess impacts of climate change on agriculture. Oct. 2004.


q. Invited participant to USA-India Workshop on Water Management, presenting a paper and advising on using system models to help optimum water management. Punjab Agricultural Univ., Ludhiana, India. Sept. 2008. Developed collaboration with scientists.

 

r. Invited participant (fully supported) to an International Conference on ‘Integrated

Agricultural Systems: Methodologies, Modelling and Measuring’, held discussions and presented a paper on ‘Models of agricultural systems to guide research and optimal management of soil-water-nutrient resources and enhance environmental quality under varying climatic conditions’, (#333). Explored research collaborations with scientists at the Scotland College of Agriculture, Edinburgh, UK. June 2009.

 

s. Invited (fully supported) by INRA, Castanet Toulouse and Grignon stations, France to develop collaboration between ARS and INRA on systems research, 2010.


t. Invited keynote speaker on “Agriculture and climate change at world level”. Symposium on "Organic Matter and Biofertilizers in Agriculture: Impact on Carbon and Water Footprints". Universidad Tecnica Frederico Santa Maria, Santiago. August 2011.

3. Offices and Committee Assignments Held in Professional and Honorary Societies

a. Member of A201 Organization, Bylaws, and Policy Committee, American Society of Agronomy. 1990-93.

b. Chair, Great Plains Agricultural Council Task Force on Computer Applications in Water Management, 1994-95.

 

c. Member Soil Science Research Award Committee, Soil Science Society of America, 1997-99.

 

d. Represented Soil Sci. Soc. Am. at the Fist Joint Congress of SSSA-German Soil Sci. Soc., Osnabrueck, Germany, September 18-22, 2000.

 

e. Member ASA Fellows Committee, American Society of Agronomy, 1999-2001

 

f. Organizer of ASA Symposium on Applications of System Models. Minneapolis, MN.

2000.

 

g. Organizer of SSSA Symposium on Quantifying Management Effects. Charlotte, NC. 2001.

 

h. Member of the Soil Sci. Soc. Am. Journal Committee to review the scope of the journal. 2003.

 

i. Invited member of the Organizing Committee for ASA Symposium on “Sustainability of Agriculture, Environment, and Food Security”. Invited speaker and author on “Whole System Interaction and Modeling Essential to Agricultural Service and Technology in the 21st Century”. Nov. 2005.

j. Soil Sci. Soc. Am. Representative to AAAS (Am. Assoc. Adv. Sci.) Physics (13)

Committee, 2005-2007.

 

k. Vice Chair, Soil Physics section, International Union of Soil Science, 2008-2010.

 

l. Member, Soil Science Research Award Committee, Soil Sci. Society of America, 2011-2013.

 

m. Invited member of the ASABE Committee on Standardization of Calibration and

Validation of Water Quality Models, 2011-2012.

 

n. Community Leader for the Community on ‘Application of System Models in Field

Research’, American Society of Agronomy. 2011-2013.

 

o. Chair, ASA-SSSA-CSSA Ad-hoc Committee to evaluate a ‘Proposal on e-publication of modules and datasets’ by the Tri-societies. 2010-2011. Recommended e-publications.

 

4. Participation in Professional Meetings, Technical Conferences, Workshops, etc.:

 

a. American Society of Agronomy – Soil Science Society of American (1969-present). Attended 35 meetings and made 33 presentations. (co-author on 100+ presentations).

 

b. American Geophysical Union (1976-present). Attended 16 meetings and gave 11

presentations.

 

c. American Society of Agricultural Engineering (1981-2000). Attended 5 meetings and gave 4 presentations.

 

d. Soil Conservation Society of American (non-member). Attended 2 meetings and gave 2 presentations.

 

e. Attended International Symposium on Isotope and Radiation Techniques in Soil Physics and Irrigation Studies, organized by the International Atomic Energy Agency and the FAO, in France, 1983, and presented a paper.

 

f. W-155/188 and S-186 Regional Multi-State Research Committee Workshops (1981- present). Attended 8 meetings and gave 8 presentations.

 

g. Attended Hawaii Subsurface Water Dynamics Workshop, organized and chaired a session on unsaturated flow problems. Honolulu, HI. 1977. Attended ARS-SCS workshop on hydrologic classification of soils, and present a paper. Lincoln, NE, 1980.

 

h. Attended International Symposium on Rainfall-Runoff Modeling, Mississippi State

Univ., 1981, and presented a paper.

 

i. Attended Soil Erosion-Productivity Workshop, West Lafayette, IN. 1981, and presented a paper.

 

j. Attended a general session of Korean Society of Soil Science and Fertilizers, July 16, 1983. Delivered an invited special lecture and received an award and a plaque.

 

k. Attended Agricultural Research Institute workshop on Research Needs for Unsaturated Zone Transport Modeling of Agricultural Chemicals. Nov. 2-4, 1987. Annapolis, MD, and served as discussion group leader.

 

l. Invited speaker in a workshop on Aggregate Stability and Infiltration, organized by Kearney Foundation of Soil Science, University of California, Davis. March 26, 1987. The incumbent spoke on "Infiltration through Crusts and Seals," following which he led an extended discussion on the methods of measurement and characterization.

 

m. Co-organized International Conference on Infiltration Development and Applications, Honolulu, HI. Jan. 6-9, 1987, and presented a paper.

 

n. Attended International Conference on Dryland Farming, Amarillo, TX. Aug. 15-19, 1988, and presented a paper.

 

o. Attended International Symposium on Managing Sandy Soils, Jodhpur, India. Feb. 6-10, 1989, and presented a paper.

 

p. Invited to International Symposium on Crusted Soils, Athens, GA. May 30-31, 1991. Presented a paper and wrote a book chapter on "Flow Through Crusted Soil." (#64).

 

q. Co-organized and participated in the 1993 International Groundwater Modeling Center Modeling Conference, Golden, CO. June 9-12, 1993.

 

r. Organized and participated in the Great Plains Agricultural Council Workshop on

Computer Applications in Water Management, and presented the opening lecture.

 

s. Hosted the 26th Annual Biological Systems Simulation Workshop, organized chaired a symposium on the Effects of Management Practices on Soil-Plant Processes, and presented a paper. Fort Collins, CO. April 9-11, 1996. Hosted 36th Annual Conference, April, 2006.

 

t. Chaired and participated in the national ARS Workshop on "Real-World Infiltration," and presented an opening lecture. Pingree Park, CO. July 22-26, 1996.

 

u. Attended the EUROPTA Conference on Remote Sensing for Agriculture, Ecosystems, and Hydrology. Barcelona, Spain, Sept. 21-25, 1998, and presented a paper.

 

v. Presented a lecture on “Applications of agricultural system models in research and management”, Lisbon Technical University, Lisbon, Portugal. April 2000.

w. Presented a lecture on “The ARS RZWQM and GPFARM models” CSIRO, Toowoomba, Australia. March 2000.

 

x. Attended the 4th International Conference on Soil Dynamics, Adelaide, Australia. March 26-30, 2000, and presented a paper.

 

y. Organized an international symposium on “Use of Agricultural System Models in Field Research, Technology Transfer, and Decision Support”, 2000 ASA-SSSA-CSSA meetings, Minneapolis, MN. 18 invited speakers were among the best in the world.

Attended by 60-100 people.

 

z. Organized an international symposium on “Quantifying management effects on soil properties and processes” at 2001 the ASA-SSSA-CSSA meetings, Charlotte, NC. 10 invited speakers were among the best experts in the world. Attended by 50-75 people.

 

aa. Organized an international workshop on “Applications, Enhancements, and

Collaborations of RZWQM and GPFARM”, Fort Collins, CO, 2004.

 

bb. Convenor of IUSS poster Symposium on “Synthesis, Modeling, Applications of

Disciplinary Soil Scienec Knowledge for Soil-Plant-Water-Environment Systems”,

World Congress of Soil Science, Philadelphia, PA, 2006.

 

cc. Organizer of the National Crop Simulation Workshop (ASA, A3), 1996 and 2006, that were focused on improving management and water stress response of models.

 

dd. Organizer of symposium on “Water Crisis in Agriculture: How to produce more with less” at the AAAS annual meeting, San Francisco, 2007.

 

ee. Co-Convenor, SSSA symposium on “Quantifying and understanding plant N uptake for system modeling” 2006. Published as CRC book 2009.

 

ff. Co-Convenor of a symposium on “Enhancing Understanding and Quantification of Soil-Root Growth Interactions”, and of a special session on “Enhancing and Facilitating the Use of System Models in Field Research”, for ASA-SSSA-CSSA meetings, 2009.

 

gg. Organized 1st International Workshop on Component-Based Natural Resources

Modeling”, Fort Collins, CO, 2009.

 

hh. Convenor of a IUSS (Int. Union Soil Sci.) symposium on ‘Optimizing water use with soil physics’, Brisbane, Australia, 2010.

 

C. Advisory and Consulting Activities:

 

1. Professional Advisory and Consulting Activities

 

Have 40+ professional advisory and consulting activities, of which the following are the most significant:

 

a. Served as International Atomic Energy Agency (IAEA) expert in South Korea from May 29 to August 24, 1983. Assisted staff at the National Institute of Agricultural Sciences in initiating a sound program of research on soil-water-plant relationships. Instructed in calibration of neutron and gamma gauges and training of staff. Studied country-wide problems of water-soil-nutrient conservation and management, and prepared a report for the Government of Korea. Presented three seminars on my work. The IAEA was very complimentary of incumbent's work. On the incumbent's recommendations his colleague, Dr. R.G. Menzel, was sent by IAEA as expert in 1984 to work further on the above project. The IAEA invited the incumbent to undertake similar missions to Sri Lanka, Bangladesh, and Tunisia, which were declined.

 

b. Consulted with scientists in Japan at the National Research Institute of Agricultural Engineering, Tsukuba, and Okayama University, August 26 to September 1, 1983, on use of modern soil physics approaches for soil-water problems of Korea and Japan. Presented invited seminars on current research and participated in the subsequent discussion sessions at both these institutions.

 

c. USDA Consultant to India: Consulted with scientists in India at the Indian Agricultural Research Institute, New Delhi, Central Soil and Water Conservation and Training Institute, Dehradun, and Himachal Pradesh Agricultural University, Palampur, June 1987 on: (1) Recent techniques developed by the incumbent for easier determination of soil hydraulic properties; and (2) use of computer models of the soil-water processes, using the above properties, for improved management of water and applied chemicals. Presented seminars and participated in the discussion sessions organized by the institutions. Assessed the possibility of one or more USDA-India collaborative research projects under PL 480. This was done with prior consultations with Dr. Robert Jackson, Director of the Far-East Regional Research Office of the USDA in New Delhi. Two potential specific research topics for collaboration work were identified and reported to Dr. Jackson.

 

d. Served as an Associate Editor for Soil Science of America Journal (SSSAJ) for six years, 1987-1992. In this capacity, was responsible for evaluation of manuscripts in soil physics submitted for publication, by own reviews, and soliciting reviews of experts in specific areas, and their final approval. Over the years, has served as a reviewer for the above journal, Water Resources Research, Soil Science, and several other journals. One associate editor wrote to the incumbent's Lab Director that the incumbent was the most thorough and objective reviewer he had worked with. --Served as Technical Editor of SSSAJ for three years, 1994-96. Incumbent handled all manuscripts submitted for soil physics through working with ten Associate Editors. He provided initial comments for all manuscripts and had the responsibility to make final judgment and decision to reject or revise on problem manuscripts. --Served as Book Review Editor for the SSSAJ for three years, 2005-2007. Responsible for selecting and inviting books for Review articles, reading the articles and suggesting changes, and approve them for publication. The Book Reviews covered all fields of soil science, beyond the incumbent’s field of research.

 

e. Serving as Series Editor for the new ASA-SSSA-CSSA book series on “Advances in

Agricultural Systems Modeling: Interdisciplinary Research, Synthesis, and

Applications”, 2008-present. The incumbent proposed this series and the Tri-Societies approved it. Volume 1 entitled ‘Response of Crops to Limited Water’ was published in 2008. Volume 2 entitled ‘Methods of Introducing System Models into Agricultural Research’ published in 2011. He develops proposal for each volume and invites the best contributors from around the world. The series will cover all different areas of agriculture, including cropping systems, rangeland/pastures-livestock systems, insects and diseases, weeds/invasive species, and climate change, well beyond the incumbent’s field of research. See Volume 1 on the Societies’ website: https://portal.sciencesocieties.org/Purchase/ProductDetail.aspx?Product_code=2eba374c-85b5-dd11-b243-0013210e308c

 

f. On invitation, served as On-Site Expert Panel to review research programs of the following ARS Units: (1) Northeast Watershed Research Center, University Park, PA,

May 1987; (2) Crop Simulation Research Unit, Mississippi State, MS, March, 1996; and (3) Wind Erosion Research Unit, Manhattan, KS, Oct. 2005. Analyzed the Unit's research for the past several years and their plans for the next five years, gave a critique and made recommendations.

 

g. Served as an invited FAO Consultant to India for use of models to manage salinity under irrigation. Presented six lectures and a 3-day workshop to scientists at the Central Soil Salinity Research Institute, Karnal, India, on modeling irrigation—salinity development relationships and potential remedies using the ARS Root Zone Water Quality Model. Aug.-Sept. 1990.

 

h. Provided invited expert consultation to FAO on use of models to guide the application of N fertilizers and pesticides with irrigation water with RZWQM. Presented a paper on “Modeling the behavior of fertilizers and pesticides in relation to chemigation” at a workshop, Cairo, Egypt, Sept. 8-11, 1991. (#235).

 

i. On NPL request, organized and coordinated an ARS-wide workshop on "Real World Infiltration," involving spatial and temporal variability in infiltration attended by 36 scientists, published its proceedings, and then led and coordinated the development of ARS Strategic Plan for Infiltration. Research, 1996-97. This plan will address needs of several national programs in the new structure. (#254).

 

j. Organized Interagency (ARS-NRCS-USGS-German) International Workshop on the development of a Modular Modeling Framework for agricultural, hydrologic, and environmental systems, September, 1997, Fort Collins, CO. Attended by 50  scientists and 5 NPL’s. The proceedings and final decisions of this workshop are providing guidelines for the coordinated modular framework development by the four agencies. Incumbent is chair of the coordinating committee. 1997-present.

 

k. Consulted on and conducted an invited workshop on how to use the ARS Root Zone Water Quality Model, at the Swiss Federal Institute for Environmental Science and Technology (EAWAG), Zurich, Switzerland; discussed collaborations. Sept. 9-11, 1998.

l. Served as a nominated member of the NRCS-ARS-CSREES Partnership Management Team (PMT). 1995-2005. The team has developed and executed comprehensive procedures to determine the NRCS field research and technology needs, prioritized those needs through peer panels, arranged to meet those needs through ARS, CSREES or other means, and provided oversight on the progress. The PMT is, thus, coordinating interagency efforts to assure that ARS and CSREES research addresses customer needs.

 

m. The GPSR/ASR Unit took leadership in helping the NPS organize a national workshop of customers, stakeholders, and scientists to develop Decision Support Systems component of the ARS Integrated Farming National Program. The incumbent served as Chair of the 7-member Planning Committee. 1999-2000. The Committee steered the development of strategic plan of this program component for the next 10 years. Co-Leader of the Models and DSS team for this NP.

 

n. The incumbent served on the Steering Committees for developing Watershed Processes and Characterization National Program and water quality components of the Water Quality and Management National Program. 1998-2000. Co-Leader of the initiative on ARS models, decision support tools, and databases for this Program. Served on the Steering Committee to organize a workshop for the Global Climate Change National Program; presented a key talk on synthesis, integration, and modeling of experimental data. Denver, CO. April, 2001. Co-Leader of the synthesis, integration and modeling team.

 

o. On invitation (with full support) from the Chinese Academy of Sciences, led a team of 4 colleagues to China. Provided advice and training on using RZWQM and GPFARM to 60+ scientists. Presented 5 seminars on the use of the models. October 9-26, 2002. Invited by the China Academy of Sciences and China Agricultural  university to advise on integrating system models with field research to enhance and extend research for managing limited water and water quality in China. Gave lectures at 5 locations on the subject. 3 weeks in May 2008.

 

p. Steering Committee for developing a multi-Location ARS-NRCS national project on CEAP (Conservation Effects Assessment Project), 2003. Co-Team Leader for developing a sub-project “Modularization, Integration, and Development of Improved Regionalized Watershed Models for Future Assessments at Different Scales” for CEAP, 2003-2011. Co-Team Leader to accomplish this project.

 

q. Consulted with/advised the U.S. EPA over the years (1992-2008), pesticide industry (Byer CropScience, 2002-present) and the California Dept. of Pesticide Regulations (2009-present) on simulating pesticides in ground and surface waters with the help of RZWQM mode for pesticide registration and environmental protection.

 

r. International visitors, who spent one month or more to work with incumbent and the system modeling- 14 (10 totally at their own expense, 4 provided just living allowance); 20+ other visitors for shorter periods. They were from China, India,

Portugal, Denmark, and Bulgaria. Their objective was to work in our systems modeling program and learn the use of the system models in their research for soil-water-cropclimate management on return to their countries. During their visit, they focused on exploring different components of the model of special interest to them, in the whole system context: effects of various management practices on water use and water quality, effects of soil type, simulation of nitrogen chemistry and management, soilpesticide dynamics and their transport to runoff and ground water through macropores, plant response to water stress and energy balance, crop rotations and optimum scheduling of water and nitrogen, cover crops and controlled drainage, water and temperature in frozen soils, climate change effects on evapo-transpiration and crop growth, and effects of Russian wheat aphis and weeds. Most of them were very productive as evidenced by the journal papers in incumbent’s publication list with their names in italics. Their work advanced the ARS system models and their applications. Their visits also enhanced their research productivity and advanced their careers back home. Eight of the visitors are continuing collaboration with the incumbent and team in advancing the use of system models for management of natural resources:

S. Rousseva, Poushkarov Soil Sci. and Yield Programing Institute, Bulgaria, IAEA Fellow, 1986-1987 (1 year);

Soren Hansen, Royal Vet. and Agric. University, Denmark, 1991 (6 months);

Qingli Ma, Zhejiang University, China, 1991-1994 (3 years);

Rosario Cameria, Lisbon Technical University, 1995 (2 months), 1996 (2 months),

1997 (2 months), 1999 (1 month);

Paulo Faria, Lisbon Technical University, 1999 (1 month);

Qiang Yu, Chinese Academy of Sciences, Institute of Geographic Sciences, Beijing, 2003 (6 months);

Chunsheng Hu, Chinese Academy of Sciences, Institute of Agric. Modernization, Shijiazhung, 2002 (3 months), 2003-2004 (3 months);

S. Chander, Indian Agricultural Res. Institute, New Delhi; Govt. of India Fellow, June- August 2003 (3 months);

Longhui Li, Chinese Academy of Sciences, Beijing, 2007 (6 months);

Quan Xiao Fang, Chinese Academy of Sciences, Beijing, 2009-2010 (1 year); Zizhong Li, China Agric. Univ., Beijing, 2011 (1 year);

Adlul Islam, Indian Council of Agric. Research, India; FAS Fellow 2011 (4 months);

Kelin Wu, China Agric. Univ., Beijing, 2011-12 (6 months).

 

---International Visitors who came to work with the team on incumbent-led OMS project, more than a month on their own expense or with partial living support (several more visited for a week or more). They advanced the OMS technology and are continuing collaboration with us as they employ OMS in their countries:

 

Mercel Wetzel, Ph.D. Student, Univ. of Jena, Germany, 2010 (partial living support) Holm Kipka, Ph.D. student, Univ. of Jena, Germany, 2010 (partial living support) Peter Krause, Asst. Prof., Univ. of Jena, Germany; now with State Environmental Agency, Thueringia, Germany, 2011 Franka Ginter, Univ. of Jena, Germany, 2011(partial living support)

Axel Hunz, Univ. of Jena, Germany, 2011 (partial living support)

Giuseppe Formetta, Ph.D. student, Univ. of Trento, Italy, 2012 (3 months)

 

s. National visitors, who spent a month or more, to work with incumbent and the system modeling, at their own institution’s expense: 7. 25+ others for shorter periods. Their interest was primarily on using and help improving models for effects of management on water and water quality and crop production. Three of the ARS visitors have used the models extensively, greatly advanced their research objectives and their productivity, and continue to actively collaborate with us (Timlin, Malone, Nielsen):

Dennis Linden, ARS St. Paul, MN, 1993-94 (6 months);

Dennis Timlin, ARS, Beltsville, MD, 1996 (4 months);

Jim Bonta, ARS, Coshocton, OH, 1996 (4 months);

Rob Malone, ARS, Coshocton, OH and Ames, IA, 1998-present (10+ weeks);

Bob Mansell, University of Florida, Gainesville, 2000 (3 months);

David Nielsen, ARS, Akron, CO, 2001-present (6 weeks, several occasions)

Gary Heathman, ARS, West Lafayette, IN, 2002-23 (1+ month)

 

t. Incumbent has worked with and helped many younger scientists in their careers. This was brought about by unselfishly sharing expertise, mentoring, collaborative research, and/or joint development of process models and their application to field research data. Among them are the following scientists:

Current and prior ARS scientists (14+): Williams, Naney, Heathman, Smith, Timlin, L. Ma, Sharpley, Green, Ascough, Farahani, Dunn, Derner, D. Nielsen, Malone, +. In addition, trained and helped numerous (100+) other scientists all over the world in using the RZWQM model (website). Some of them I worked with closely are now

outstanding GS-15 (Timlin, Ma, Green) or GS-14 scientists (Malone, Nielsen).

 

--ARS support scientists (7): Ross, Barnes, Lehman, Rojas, Johnsen, Sherrod, Ferreira.

 

2. Special Assignments:

·         Served as invited Chair of a 21-member interagency Task Force of the Great Plains Agricultural Council, that organized a workshop on Computer Applications in Water Management, attended by more than 100 professionals, and published its proceedings. (#246). Received a letter of commendation from the Council. 1995.

·         At the request of NPL (Amerman), spent about 4 weeks (a week at a time) to help NPL organize national workshops noted above, 1998-2001. Also, helped NPL organize a workshop of ARS developers of user software (Sept. 2000), that lead to development of ARS Software Policy and proposal for a National Software Support Center.

 

D. Other:

 

1. Educational Background:

 

·         1951-54: University of Delhi, India; major, Agronomy; minor, Chemistry; B.S. (Hons.). 1954.

·         1959-61: Indian Agricultural Research Institute, New Delhi; major, Agronomy; minor, Chemistry; M.S. 1961.

·         1963-65: Indian Agricultural Research Institute, New Delhi. 21 credit hours in chemistry, soil physics and statistics.

·         1965-68: University of California, Davis; major, Soil Physics; minor, Mathematics; Ph.D. 1968.

·         1985-86: Princeton University, Princeton, NJ. Attended classes in six advanced courses in numerical methods, math, and stat. methods of Engineering analysis, groundwater flow, and partial differential equations. Also learned finite-element simulation of water flow and transport.

 

2. Research Experience:

·         1962-63: Assistant Professor, Himachal Agricultural College. Solan, India.

·         1968-71: Postdoctoral Research Associate, Purdue University. West Lafayette, IN.

·         1972-76: Assistant Soil Scientist, University of Hawaii. Honolulu, HI.

·         1976-78: Associate Soil Scientist, University of Hawaii. Honolulu, HI. Associate Professor of Soil Science, Univ. of Hawaii. Hilo, HI.

·         1979-81: GS-13, Soil Scientist, USDA-ARS. Durant, OK.

·         1981-82: GM-13, Soil Scientist, USDA-ARS. Durant, OK.

·         1983-87: GM-14, Soil Scientist, USDA-ARS, Durant, OK.

·         1988-91: GM-15, Soil Scientist, USDA-ARS. Durant, OK. Acting Research Leader for six months in 1990-91.

·         1991-Present: GM-15, Supervisory Soil Scientist and Research Leader USDA-ARS. Fort Collins, CO.

3. Other Significant Information:

 

a. Incumbent’s Leadership Contributions to RZWQM: Incumbent was a team member selected by NPLs to build a Root Zone Water Quality Model (RZWQM) in 1989-90. The model was still under development in 1991 when he was appointed the RL of the Unit and team leader for RZWQM. Incumbent contributed several science components (given below), and worked with the team in science issues to complete first draft of the model in 1992, used in the MSEA project. He then invited two other ARS scientists and contributed science to strengthen pesticides (Wauchope) and energy balance and frozen soils (Flerchinger) components. He attracted bright postdocs, guided and worked with them to strengthen evapotranspiration (Hamid Farahani), residue cover effects (Aiken), and water stress, and canopy and residue interception (Kozak). He developed cooperative research with: Iowa State Univ. (Kanwar), where several students and postdocs tested and improved parts & model as a whole against their field data; Univ. of Georgia (Hoogenboom) provided better crop growth components; Univ. of Florida (Mansell) added soil erosion, and Technical Univ. Lisbon, Portugal (Cameira), tested several parts of the model. Attracted Liwang Ma to the Unit as postdoctoral (now permanent GS-15), mentored & worked with him, in enhancing several model components and adding new components (see below); worked with ARS scientists outside the Unit (Malone, Nielsen, Jabro), and collaborated with China (C. Hu, K. Hu, Yu, Fang, L. Li, and Z. Li) and India (Islam), that advanced applications as well as science of the model. Incumbent inspired and championed model applications in field research, training numerous groups and advising 200+scientists in using the model. The incumbent is an author/co-author of 82 journal papers out of the total 90 journal papers published on RZWQM/2 in the ASR Unit, indicating his major role.

 

b. Science Components of RZWQM Contributed by Incumbent: water and chemical transport, estimation of hydraulic parameters and changes with  tillage/reconsolidation; macropore flow; chemicals in runoff; tile flow; and parts of evapotranspiration from partial canopy and residue covers, heat transport, pesticides’ kinetics, plant uptake, residue decomposition, and management practices (crop rotations; tillage- no tillage; manure, fertilizer, pesticide, & irrigation applications, chemigation--timing. amounts, methods), and integration across components. Many components have since been collaboratively tested and further improved jointly by Dr. Ma and incumbent; including the C/N routines for better simulation of crop residues, manures and N in soil and water; RZWQM-DSSAT hybrid to have crop-specific growth models; RZWQM-SHAW hybrid for canopy temperature; and new crops (triticale, proso millet, foxtail millet, canola). As a result, the RZWQM is unique in evaluating a whole range of cropping systems and management practices that affect water, water quality, and production, identifying the best crops, varieties, & management for various soils and climates. A simple economic analysis is used with model results to assess economic impacts. The USGS compared five national system models for assessing water use and water quality, and selected RZWQM as the best.

 

c. Incumbent’s Leadership and Contributions for GPFARM Decision Support System: As RL, the incumbent set up the team, guided development of the work plan, and contributed to /guided the development of several components. This model is a simpler version of RZWQM, so that it can be run with easily available input data, but includes economics and rangeland processes and animal production. The science components contributed by the incumbent were simplified versions of the components described above for RZWQM. He attracted an excellent postdoctoral (Andales) and worked with him closely in testing and improving the model against field data. He especially took personal leadership in testing and improving the GPFARM-Range/animal part of the GPFARM, working closely with Andales, 24

visiting scientists (Adiku, Qi), and field collaborators (ARS scientists at Cheyenne, WY, Woodward, OK, and Miles City, MT). Uniqueness of GPFARM-Range lies in its ability to rigorously evaluate the effect of grazing management practices on soil water, forage and animal production, soil C, and climate change effects. Incumbent is co-author of 10 journal papers out of the total of 13 published on GPFARM, again indicating his major role.

 

d. Incumbent’s Leadership and Contributions for OMS: Organized an international

workshop to explore more efficient ways of building complex models in 1997 (4C-1j). Led to consensus to develop a uniform and shared object based modeling system (OMS) for building models of natural resource systems from a library of science modules, with uniform parameter estimation and analysis tools. As follow up, incumbent created a partnership with NRCS, USGS, and FSU (Univ. of Jena, Germany) for this purpose. He sought and obtained funding from NPLs to bring in Dr. Olaf David on sabbatical from FSU for two years. Dr. David came in 2000 and became the architect of our OMS framework. Incumbent also sought funds from ARS and partners to hire IT support for Dr. David. The progress and potential value of OMS persuaded Dr. David to resign from his job at Jena and stay with us. Incumbent organized quarterly (less often later) meetings of the partners and NPLs to review progress and provide guidance. In between, he had frequent meetings with the OMS team on technical issues and provided leadership and encouragement. He recruited and guided an IT specialist and a postdoc to modularize ASRU models in OMS format. He initiated and guided a new 5-year ARS project for enhancing OMS and for ASRU SYs to develop a watershed model in OMS, which is just completed.

 

e. The following postdoctoral scientists, even though supported by ARS to varying degrees, wanted to work with incumbent to learn modeling of agricultural systems, contributed greatly to improvement of the various model components, advanced application of models to practical problems, and coauthored numerous journal publications (see the pub. listed with them as coauthors). They continue to use system models (RZWQM/RZWQM2) in their research for natural resources management and enhance their productivity:

--Federal postdoctoral scientists (8): Dennis Timlin, 1989-1991; Joe Benjamin, 1991-1996; Hamid Farahani, 1994-1996; Rob Aiken, 1992-1998; Liwang Ma, 1996-2000; Allan Andales, 2001-2003 and 2004-2006; Joseph Kozak, 2004-2006; Jonghan Ko, 2009-2010. Four became ARS scientists, three university professors, and one industry scientist.

- -Postdoctoral scientists hired under a Specific Cooperative Agreement with Colorado State University, but who worked with the incumbent (6): Macmood Nachabe, 1995 and 1997- 1998; H. Ruan, 1995-1999; Olaf David, 2000-present

- -Jointly supported postdocs with Iowa State Univ. or at NASA-Greenbelt, MD, who worked with cooperators and incumbent, with periodic visits to Fort Collins (4): Pyush Singh, 1992- 1994 (2+ years); Vijay Kumar, 1994-1996 (1.5 years); Nandesh Mattakali, India, 1997 (1 year); Allah Bakhsh, 1998-2001 (3+ years)

 

f. Service on the Graduate faculties and advising graduate students:

 

Member of the Graduate Faculty of the University of Hawaii, 1973-78. Faculty Affiliate in the Departments of Civil Engineering and Soil and Crop Sciences at Colorado State University, 1991-present.

International academic advisor, Chinese Academy of Sciences, Comprehensive Yucheng Experiment Station, 2003-2008.

Adjunct Professor, College of Natural Resources and Environmental Sciences, China

Agricultural University, Beijing. 2006-present.

---Graduate students who wanted to work with incumbent as committee member or as coadvisor (see pubs. with them as authors):

University of Hawaii: Chang (co-advisor), Rao, Balasubramanian, Rehman.

Lisbon Technical University: Cameira (essentially co-advisor).

University of Oklahoma: Heathman (essentially co-advisor).

Colorado State University: Meier (co-advisor), Shaver (co-advisor), Fiedler (co-advisor), Meng (co-advisor), Sherrod, Saseendran.

g. Established the Soil Science Society of America, L.R. Ahuja Agricultural System Modeling Award. The award is available annually for a selected outstanding scientist who integrates the use of system models with their experimental research and advances the system models and their applications in agriculture. Incumbent and ASR colleagues also teach system modeling as part of environmental science courses at Colorado State University in 2004 to present.

 

h. The ASR (formerly Great Plains Systems Research) Unit’s program has been the subject of the following articles written in popular magazines/press:

 

Agricultural Research magazine: 11

ARS News Service: 4

Other popular publications: 8

 

For details see: http://ars.usda.gov/Services/docs.htm?docid=21863

 

i. Manuscripts submitted for publication but not yet accepted:

 

1. Saseendran S.A., Ahuja, L. R., Nielsen, D. C., Ma, L., and Lyon, D. Development of a decision support system for summer crop selection in the Central Great Plains. Field Crops Res. (in review). 2011.

2. Derner, J.D., Augustine, D.J., Ascough, J.M., and Ahuja, L.R. Why don’t models have more utility for rangeland management? J. Rangeland Ecology and Management (Invited Special paper). 2011.

3. Li, Zizhong, Ma, L., Flerchinger, G.N., Ahuja, L.R., and Wang, H. Simulation of overwinter soil water and soil temperature with SHAW and RZ-SHAW. Soil Sci. Soc. Am. J. Submitted. 2011.

4. Islam, A., Ahuja, L.R., Garcia, L.A., Ma, L., Saseendran, S.A. Modeling the Effect of Elevated CO2 and Climate Change on Potential Evapo-transpiration in the semi-arid Great Plains. Trans. ASABE. Submitted. 2012.

5. Islam, A., Ahuja, L.R., Garcia, L.A., Ma, L., Saseendran, S.A., Trout, T. Impact of climate change on irrigated corn production in the Central Great Plains. Agric. Water Manage. Submitted. 2012.

6. Ma, L., Ahuja, L. R., Nolan, B. T., Malone, R. W., and Trout, T. J. 2012. Root Zone Water Quality Model (RZWQM2): Model Use, Calibration and Validation. Trans.

ASABE. (submitted Oct. 13, 2011).

7. Ma, L., and Ahuja, L. R. 2012. Comparing various statistics for evaluating simulation results in systems modeling. SSSAJ. 2012 (submitted on Nov. 28, 2011).

 

j. Had a total of 3 CRADAS, 2 Grants, 5 Reimbursable and 25 Specific Cooperative Research Agreements, of which the following are the most significant:

 

CRADAs:

·         Regenesis Management Group, 2010-2013. PI: Laj Ahuja and Gale Dunn. Documenting water savings from deficit irrigation and development of a decision support tool. $62,500 a year to ASR Unit.

·         Decision Commerce Group, 2005-2010, PI: Gale Dunn, The Merging of GPFARM with Commercially Developed Software for Agricultural Sustainability and Optimization.

·         Water Resources Publications, LLC, Highlands Ranch, CO, 1995-2000. Publication of the Root Zone Water Quality Model (RZWQM).

 

Grants:

·         RMA, $820,132; 2005-2008, PI: Gale Dunn and Allan Andales (Postdoc)/Laj Ahuja

·         CSREES-NRI, $220,000; 1995 – 1997, PI: Joe Benjamin (Postdoc)/Ahuja.


Reimbursable Agreements:

·         NRCS, $200,000; 2003-2005, PI: Carlson/Werner and Ahuja, The Object Modeling System (OMS): An Advanced Computer Framework for Natural Resources Technology Models and Tools.

·         EPA, $95,000; 2003-2005, PI: Russo and Ahuja, Develop a Library of Computer Software Routines for Spatial Visualization and Geodata Processing

·         USGS, $28,000, 2003-2004, PI: Leavesley and Ahuja, Develop Software for OMS

·         NRCS, $500,000; 2003-2011, PI: Ahuja and Ascough, The Object Modeling System (OMS)/CEAP Project. Received through ARS Headquarters.

·         NRCS, $ 326,000; 2011-13. PI: Green (Ahuja, RL), Conservation Delivery Streamlining Initiative-Object Modeling System.

 

E. PUBLICATIONS

 

Peer-Reviewed Journal Articles and Patents

 

1. Ahuja, L.R., and Gautum, O.P., Response of hybrid maize to zinc fertilization. Current Sci. 12:473-474. 1961.

 

2. Gautum, O.P., Sexana, M.C. and Ahuja, L.R., Suitability of soils for irrigation-land classification. Agric. Engr., (India):77-80. 1961-62.

 

3. Gautum, O.P., Ahuja, L.R. and Mukhopadhyay, D., Response of hybrid maize to micro-nutrient elements. J. Indian Soc. Soil Sci. 12:411-421. 1964.

 

4. Ahuja, L.R., and Singh, M., Evaluation of the effects of different crop rotations on soil productivity. J. Soil Water Conservation. (India). 13:16-24. 1965.

 

5. Jogi, B.S., and Ahuja, L.R., Micro-nutrient fertilization of hybrid maize in hill soils. Sci. Cult. 31:95-96. 1965.

 

6. Ahuja, L.R., and Swartzendruber, D., An improved form of soil-water diffusivity function. Soil Sci. Soc. Am. Proc. 36(1):9-14. 1972.

7. Ahuja, L.R., and Swartzendruber, D., Effect of portland cement on soil aggregation and hydraulic properties. Soil Sci. 114:359-366. 1972.

 

8. Duchatau, P., Nofziger, D.L., Ahuja, L.R. and Swartzendruber, D., Experimental c c curves and rates of change from piecewise parabolic fits. Agron. J. 65(4):538-542. 1972.

 

9. Ahuja, L.R., A numerical and similarity analysis of infiltration into crusted soils. Water Resources Res. 9:987-994. 1973.

 

10. Ahuja, L.R., and Swartzendruber, D., Horizontal soil-water intake through a think zone of reduced permeability. J. Hydrol. 19:71-89. 1973.

 

11. Ahuja, L.R., Applicability of Green-Ampt approach to water infiltration through surface crust. Soil Sci. 118:283-288. 1974.

 

12. Ahuja, L.R., Unsaturated hydraulic conductivity from cumulative inflow data. Soil Sci. Soc. Am. Proc. 38:695-699. 1974.

 

13. Ahuja, L.R., and Romkens, M.J.M., A similarity during early stages of rain infiltration. Soil Sci. Soc. Am. Proc. 38:541-544. 1974.

 

14. Nofziger, D.L., Ahuja. L.R. and Swartzendruber, D., Flux-gradient relationships and soil-water diffusivity from curves of water content versus time. Soil Sci. Soc. Am. J. 38:17-23. 1974.

 

15. Ahuja, L.R., A one-step wetting procedure to determine both water characteristic and hydraulic conductivity of a soil core. Soil Sci. Soc. Am. Proc. 39:418-423. 1975.

 

16. Ahuja, L.R., and El-Swaify, S.A., Determining both soil-water characteristic and hydraulic conductivity at high water contents from a transient flow experiment. Soil Sci. Am. J. 121:198-204. 1976.

 

17. Ahuja, L.R., El-Swaify, S.A. and Rahman, A., Measuring hydrologic properties of soil with a double-ring infiltrometer and multiple-depth tensiometers. Soil Sci. Soc. Am. J. 40:494-499. 1976.

 

18. Ahuja, L.R., and Tsuji, G.Y., Use of Green-Ampt equation with variable conductivity. Soil Sci. Soc. Am. J. 40:619-622. 1976.

 

19. Ahuja, L.R., Dangler, E.W. and El-Swaify, S.A., Predicting runoff initiation times under field conditions in tropical (Hawaii) soils. Soil Sci. Soc. Am. J. 40:777-779. 1976.

 

20. Balasubramanian, V., Ahuja, L.R., Kanehiro, Y. and Green, R.E., Movement of water and nitrate in an unsaturated aggregated soil during nonsteady infiltration--A simplified solution for solute flow. Soil Sci. Am. J. 122:245-255. 1976.

 

21. Rao, P.S.C., Green, R.E., Ahuja, L.R. and Davidson, J.M., Evaluation of a capillary-bundle model for describing solute dispersion in aggregated soils.

Soil Sci. Soc. Am. J. 40:815-820. 1976.

 

22. Ahuja, L.R., and El-Swaify, S.A., Determining soil hydrologic characteristics on a remote forest watershed by continuous monitoring of soil-water pressures, rainfall and runoff. J. Hydrol. . 44:135-147. 1979.

 

23. Ahuja, L.R., Green, R.E., Chong. S.K. and Nielsen, D.R., A simplified functions approach for determining soil hydraulic conductivities and water characteristics in situ. Water Resources Res. 16:947-953. 1980.

 

24. Ahuja, L.R., Ross, J.D. and Lehman, O.R., A theoretical analysis of interflow of water through surface soil horizons with implications for movement of chemicals in field runoff. Water Resources Res. 17:65-72. 1981.

 

25. Ahuja, L.R., Sharpley, A.N., Yamamoto, M. and Menzel, R.G., The depth of rainfall-runoff-soil interaction determined by 32P. Water Resources Res. 17:969-974. 1981.

 

26. Chong, S.K., Green, R.E. and Ahuja, L.R., Simple in-situ determination of hydraulic conductivity by power function description of drainage. Water Resources Res. 17:1109-1114. 1981.

 

27. Sharpley, A.N., Ahuja, L.R. and Menzel, R.G., The release of soil phosphorus to runoff in relation to the kinetics of desorption. J. Environ. Qual. 10:386-391. 1981.

 

28. Sharpley, A.N., Ahuja, L.R., Yamamoto, M. and Menzel, R.G., The kinetics of phosphorus desorption from soil. Soil Sci. Soc. Am. J. 45:493-496. 1981.

 

29. Ahuja, L.R., and Ross, J.D., Interflow of water through a sloping soil with seepage face. Soil Sci. Soc. Am. J. 46:245-250. 1982.

 

30. Ahuja, L.R., Sharpley, A.N. and Lehman, O.R., Effect of soil slope and rainfall characteristics on phosphorus in runoff. J. Environ. Quality. 11:9-13. 1982.

 

31. Ahuja, L.R., Release of a soluble soil chemical from soil to runoff. Transactions of the ASAE. 25:948-953, 960. 1982.

 

32. Ahuja, L.R., Determining unsaturated hydraulic conductivity of soil during drainage under a small ring infiltrometer. J. Hydrol. 58:167-173. 1982.

 

33. Chong, S.K., Green, R.E. and Ahuja, L.R., Determination of sorptivity based on in-situ of soil water redistribution measurements. Soil Sci. Soc. Am. J. 46:235-239. 1982.

 

34. Chong, S.K., Green, R.E. and Ahuja, L.R., Infiltration prediction based on estimation of Green-Ampt wetting front pressure head from measurements of soil water redistribution. Soil Sci. Soc. Am. J. 46:235-239. 1982.

 

35. Sharpley, A.N., and Ahuja, L.R., Effects of temperature and soil-water content during incubation on the desorption of phosphorus from soil. Soil Sci. Am. J. 133:350-355. 1982.

 

36. Ahuja, L.R., Modeling infiltration into crusted soils by the Green-Ampt approach. Soil Sci. Soc. Am. J. 47:412-418. 1983.

 

37. Ahuja, L.R., Lehman, O.R. and Sharpley, A.N., Bromide and Phosphate in runoff water from shaped and cloddy soil surfaces. Soil Sci. Soc. Am. J. 47:746-748. 1983.

 

38. Ahuja, L.R., and El-Swaify, S.A., Comments on AWetting moisture characteristic curves derived from constant-rate infiltration into thin soil samples. Soil Sci. Soc. Am. J. 47:840. 1983.

 

39. Ahuja, L.R., and Lehman, O.R., The extent and nature of rainfall-soil interaction in the release of soluble chemicals to runoff. J. Environ. Qual. 12:34-40. 1983.

 

40. Ahuja, L.R., and Ross, J.D., Effect of subsoil conductivity and thickness on interflow pathways, rates, and source areas for chemicals in a sloping layered soil with seepage face. J. Hydrol. . 64:189-204. 1983.

 

41. Sharpley, A.N., and Ahuja, L.R., A diffusion interpretation of soil phosphorus desorption. Soil Sci. Am. J. 135:322-326. 1983.

 

42. Ahuja, L.R., Naney, J.W., Green, R.E. and Nielsen, D.R., Macroporosity to characterize spatial variability of hydraulic conductivity and effects of land management. Soil Sci. Soc. Am. J. 48:699-702. 1984.

 

43. Ahuja, L.R., Naney, J.W. and Nielsen, D.R., Scaling soil water properties and infiltration modeling. Soil Sci. Soc. Am. J. 48:970-973. 1984.

 

44. Smith, S.J., Ahuja, L.R. and Ross, J.D., Leaching of a soluble chemical under field crop conditions. Soil Sci. Soc. Am. J. 48:252-258. 1984.

 

45. Ahuja, L.R., Williams, R.D., Heathman, G.C. and Naney, J.W., Use of a surface gamma-neutron gauge to measure effects of tillage, cropping, and erosion on soil properties. Soil Sci. Am. J. 140:278-286. 1985.

46. Ahuja, L.R., Naney, J.W. and Williams, R.D., Estimating soil water characteristics from simpler properties or limited data. Soil Sci. Soc. Am. J. 49:1100-1105. 1985.

 

47. Heathman, G.C., Ahuja, L.R. and Lehman, O.R., The transfer of soil surfaceapplied chemicals to runoff. Transactions of the ASAE. 28:1909-1915, 1920. 1985.

 

48. Lehman, O.R., and Ahuja, L.R., Interflow of water and tracer chemical on sloping field plots with exposed seepage faces. J. Hydrology. 76:307-317. 1985.

 

49. Ahuja, L.R., Characterization and modeling of chemical transfer to runoff.

Adv. Soil Sci. 4:149-188. 1986.

 

50. Heathman, G.C., Ahuja, L.R. and Baker, J.L., Test of a non-uniform mixing model for transfer of herbicides to surface runoff. Transactions of the ASAE. 29:450-455, 461. 1986.

 

51. Celia, M.A., Ahuja, L.R. and Pinder, G.F., Orthogonal collocation and alternating direction procedures for unsaturated flow problems. Adv. Water Resources 10:178-187. 1987.

 

52. Williams, R.D., Ahuja, L.R., Naney, J.W., Ross, J.D., and Barnes, B.B., Spatial trends and variability of soil properties and crop yield in a small watershed. Transactions of the ASAE. 30:1653-1660. 1987.

 

53. Ahuja, L.R., Ross, J.D., Bruce, R.R. and Cassel, D.K., Determining unsaturated hydraulic conductivity from tensiometer data alone. Soil Sci. Soc. Am. J. 52:27-34. 1988.

 

54. Ahuja, L.R., Barnes, B.B., Cassel, D.K., Bruce, R.R. and Nofziger, D.L., Effect of assumed unit-gradient during drainage on the determination of unsaturated hydraulic conductivity and infiltration parameters. Soil Sci. Am. J. 145:235-243. 1988.

 

55. Ahuja, L.R., Naney, J.W., Williams, R.D. and Ross, J.D., Vertical variability of soil properties in a small watershed. J. Hydrol. . 99:307-318. 1988.

 

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56. Naney, J.W., Williams, R.D. and Ahuja, L.R., Variability of soil water properties and crop yield in a sloped watershed. Water Resources Bulletin. 24:281-288. 1988.

 

57. Rousseva, S.S., Ahuja, L.R., and Heathman, G.C., Use of a surface gammaneutron gauge for in-situ measurement of changes in bulk density of the tilled zone. Soil and Tillage Res. 12:235-252. 1988.

 

58. Sharpley, A.N., Smith, S.J., and Ahuja, L.R., Soluble potassium transport in agricultural runoff water. Agric.Water Mgmt. 15:37-46. 1988.

 

59. Ahuja, L.R., Cassel, D.K., Bruce, R.R., and Barnes, B.B., Evaluation of the spatial distribution of hydraulic conductivity using effective porosity data.

Soil Sci. Am. J. 148:404-411. 1989.

 

60. Ahuja, L.R., Nofziger, D.L., Swartzendruber, D., and Ross, J.D., Relationship between Green-and-Ampt parameters based on scaling concepts and field-measured hydraulic data. Water Resources Res. 25:1766-1770. 1989.

 

61. Ahuja, L.R., Modeling soluble chemical transfer to runoff with rainfall impact as a diffusion process. Soil Sci. Soc. Am. J. 54:312-321. 1990.

 

 

62. Ahuja, L.R., and Williams, R.D. Scaling soil water characteristic and hydraulic conductivity based on Gregson-Hector-McGowan approach. Soil Sci. Am. J. 55:308-319. 1991.

 

63. Ahuja, L.R., and Williams, R.D. Reply to comments on 'Scaling water characteristic and hydraulic conductivity based on Gregson-Hector-McGowan approach'. Soil Sci. Soc. Am. J. 56:1981. 1992.

 

64. Ahuja, L.R., and Swartzendruber, D. Flow through crusted soils: analytical and numerical approaches. Adv. Soil Sci.:93-122. 1992.

 

65. Timlin, D.J., Heathman, G.C. and Ahuja, L.R., Solute leaching in crop row versus interrow zones. Soil Sci. Soc. Am. J. 56:384-392. 1992.

 

66. Williams, R.D., Ahuja, L.R. and Naney, J.W., Comparison of methods to estimate soil water characteristics from soil texture, bulk density, and limited data. Soil Sci. Am. J. 153:172-184. 1992.

 

67. Williams, R.D., and Ahuja, L.R., Evaluation of similar-media scaling and a one-parameter model for estimating soil water characteristic. Soil Sci. Soc. Am. J. 43:237-248. 1992.

 

68. Ahuja, L.R., Wendroth, O. and Nielsen, D.R., Relationship between initial drainage and average soil profile saturated hydraulic conductivity. Soil Sci. Soc. Am. J. 57:19-25. 1993.

 

69. Ahuja, L.R., DeCoursey, D.G., Barnes, B.B. and Rojas, K.W., Characteristics of macropore transport studied with the ARS Root Zone Water Quality Model. Transactions of the ASAE. 36:369-380. 1993.

 

70. Smith, S.J., Sharpley, A.N. and Ahuja, L.R., Agricultural chemical discharge in surface water runoff. J. Environ. Qual. 22:474-480. 1993.

71. Williams, R.D., and Ahuja, L.R., Using a one-parameter model to estimate the soil water characteristic. Adv. Hydro-Sci. 1:485-490. 1993.

 

72. Benjamin, J.G., Havis, H.R., Ahuja, L.R., and Alonso, C.V., Leaching and water flow patterns in every-furrow and alternate-furrow irrigation. Soil Sci. Soc. Am. J. 58:1511-1517. 1994.

 

73. Timlin, D.J., Ahuja, L.R., and Ankeny, M.D., A comparison of three methods to characterize apparent macropore conductivity. Soil Sci. Soc. Am. J. 58:278-284. 1994.

 

74. Williams, R.D., and Ahuja, L.R., Using available water content with the oneparameter model to estimate soil water retention. Soil Sci. Soc. Am. J. 156:380-388. 1994.

 

75. Ahuja, L.R., Johnsen, K.E., and Heathman, G.C., Macropore transport of a surface-applied bromide tracer: model evaluation and refinement. Soil Sci. Soc. Am. J. 59:1234-1241. 1995.

 

76. Heathman, G.C., Ahuja, L.R., Timlin, D.J. and Johnsen, K.E., Surface aggregates and macropore effects on chemical transport in soil under rainfall.

Soil Sci. Soc. Am. J. 59:990-997. 1995.

 

77. Johnsen, K.E., Liu, H.H., Dane, J.H., Ahuja, L.R., and Workman, S.R., Simulating fluctuating water tables and tile drainage with the Root Zone Water Quality Model and a new model, WAFLOWM. Transactions of the ASAE. 38(1):75-83. 1995.

 

78. Ma, Q.L., Ahuja, L.R., Rojas, K.W., Ferreira, V.A., and DeCoursey, D.G., Measured and RZWQM predicted Atrazine movement in a field soil. Transactions of the ASAE. 38:471-479. 1995.

 

79. Ahuja, L.R., Ma, Q.L., Rojas, K.W., Boesten, J.J.T.I. and Farahani, H.J., A field test of Root Zone Water Quality Model--pesticide and bromide behavior. Pestic. Sci. 48:101-108. 1996.

 

80. Benjamin, J.G., Ahuja, L.R., and Allmaras, R.R., Modeling corn rooting pattern and their effects on water uptake and nitrate leaching. Plant and Soil. 179:223-232. 1996.

 

81. Farahani, H.J. and Ahuja, L.R., Evapotranspiration modeling of partial canopy/residue covered fields. Transactions of the ASAE. 39(6):2051-2064. 1996.

 

82. Ma, Q.L., Ahuja, L.R., Wauchope, R.D., Benjamin, J.G., and Burgoa, B., Comparison of instantaneous equilibrium and equilibrium-kinetic sorption models for simulating simultaneous leaching and runoff of pesticides. Soil Sci. Soc. Am. J. 161:646-655. 1996.

 

83. Nachabe, M.H., and Ahuja, L.R., Quasi-analytical solution for predicting the redistribution of surface-applied chemicals. Transactions of the ASAE 39:1659-1664. 1996.

 

84. Singh, P., Kanwar, R.S., Johnsen, K.E. and Ahuja, L.R., Calibration and evaluation of subsurface drainage component of RZWQM V. 2.5. J. Environ. Qual. 25:56-63. 1996.

 

85. Azevedo, A.S., Singh, P., Kanwar, R.S. and Ahuja, L.R., Simulating nitrogen management effects on subsurface drainage water quality. Agric. Systems 55:481-501. 1997.

 

86. Azevedo, A.S., Kanwar, R.S. Singh, P., Ahuja, L.R., and Pereira, L.S., Simulating Atrazine transport using Root Zone Water Quality Model for Iowa soil profiles. J. Environ. Qual. 26:153-164. 1997.

 

87. Benjamin, J.G., Porter, L.K., Duke, H.R. and Ahuja, L.R., Corn growth and nitrogen uptake with furrow irrigation and fertilizer bands. Agronomy J. 89:609-612. 1997.

 

88. Nachabe, M.H., Illangesekare, T.H., Morel-Seytoux, H.J., and Ahuja, L.R.,

Infiltration over heterogeneous watershed: Influence of rain excess. J.

Hydrologic Engineering 2:140-143. 1997.

 

89. Ahuja, L.R., Fiedler, F., Dunn, G.H., Benjamin, J.G. and Garrison, A., Changes in soil water retention curve due to tillage and natural consolidation. Soil Sci. Soc. Am. J. 62:1228-1233. 1998.

 

90. Benjamin, J.G., Porter, L.K., Duke, H.R., Ahuja, L.R. and Butters, G., Nitrogen movement with furrow irrigation method and fertilizer band placement. Soil Sci. Soc. Am. J. 62:1103-1108. 1998.

 

91. Cameira, M.R., Sousa, P.L., Farahani, H.J., Ahuja, L.R. and Pereira, L., Evaluation of RZWQM for the simulation of water and nitrate movement in level basin, fertigated maize in Portugal. J. Agric. Engng. Res. 69:331-341. 1998.

 

92. Farahani, H.J., Peterson, G.A., Westfall, D.G., Sherrod, L.A. and Ahuja, L.R., Soil water storage in dryland cropping systems: The significance of cropping   intensification. Soil Sci. Soc. Am. J. 62:984-991. 1998.

 

93. Kumar, A., Kanwar, R.S. and Ahuja, L.R., Evaluation of preferential flow component of RZWQM (V. 3.25) in simulating water and atrazine transport to subsurface drain lines. Trans. of the ASAE. 41:627-638. 1998.

 

94. Kumar, A., Kanwar, R.S. and Ahuja, L.R., RZWQM Simulation of NO3-N concentrations in subsurface drainage from manured plots. Trans. of the ASAE. 41:587-597. 1998.

 

95. Ma, L., Shaffer, M.J., Boyd, J.K., Waskom, R., Ahuja, L.R., Rojas, K.W. and

Xu, C., Manure management in an irrigated silage corn field: experiment and  modeling. Soil Sci. Soc. Am. J. 62:1006-1017. 1998.

 

96. Ma, L., Scott, D., Shaffer, M.J. and Ahuja, L.R., RZWQM simulation of water and nitrate movement in a manured tall fescue field. Soil Sci. Soc. Am. J. 163:259-270. 1998.

 

97. Mattakali, N.M., Engman, E.T., Ahuja, L.R., and Jackson, T.J., Microwave remote sensing of soil moisture for estimation of profile soil properties. Intern. J. Remote Sensing. 19:1751-1767. 1998.

 

98. Mattakali, N.M., Engman, E.T., Jackson, T.J. and Ahuja, L.R., Microwave remote sensing of temporal variations of brightness temperature and nearsurface soil water content during a watershed-scale experiment, and its application to the estimation of soil physical properties. Water Resources Res. 34:2289-2299. 1998.

 

99. RZWQM Team (Hanson, J.D., Ahuja, L.R., Shaffer, M.J., Rojas, K.W., DeCoursey, D., Farahani, H., Johnsen, K.E.), RZWQM: Simulating the effects of management on water quality and crop production. Agric. Systems. 57:161-195. 1998.

 

100. Timlin, D.J., Ahuja, L.R., and Heathman, G.C., Preferential transport of a bromide tracer applied in a pulse of ponded water. J. Environ. Qual. 27:505-514. 1998.

 

101. Bakhsh, A., Kanwar, R.S. and Ahuja, L.R., Simulating the Effect of Swine Manure Application on NO3-N Transport to Subsurface Drainage Water. Transactions of The ASAE. 42:657-664.1999.

 

102. Farahani, H.J., Buchleiter, G.W., Ahuja, L.R., Peterson, G.A. and Sherrod, L.A., Seasonal evaluation on Root Zone Water Quality Model in Colorado. Agron. J. 91:212-219. 1999.

 

103. Kumar, A., Kanwar, R.S., Singh, P. and Ahuja, L.R., Evaluation of the Root Zone Water Quality Model for predicting water and NO3-N movement on Iowa Soils. Soil and Tillage Research. 50:223-236. 1999.

 

104. Ma, L., Peterson, G.A., Ahuja, L.R., Sherrod, L., Shaffer, M.J. and Rojas, K.W., Decomposition of surface crop residues in long-term studies of dryland agroecosystems. Agronomy J. 91:393-401. 1999.

 

105. Ma, Q.L., Hook, J.E. and Ahuja, L.R., Influence of three parameter conversion methods between van Genuchten and Brooks-Corey parameters on water balance predictions. Water Resource. Res. 35:2571-2578. 1999.

 

106. Nachabe, M.H., Ahuja, L.R. and Butters, G., Bromide transport under sprinkler and flood irrigation for no-till soil condition. J. Hydrology. 214:8-17. 1999.

107. Pechepsky, Y.a., Timlin, D.J. and Ahuja, L.R., Estimating saturated soil hydraulic conductivity using water retention data and neural networks. Soil Sci. Soc. Am. J. 164:552-560. 1999.

 

108. Timlin, D.J., Ahuja, L.R., Pachepsky, Ya., Williams, R.D., Gimenez, D., and

Rawls, W.J., Use of Brooks-Corey parameters to improve estimates of saturated hydraulic conductivity from effective porosity. Soil Sci. Soc. Am. J. 63:1086-1092. 1999.

 

109. Bakhsh, A., Kanwar, R.S., Jaynes, D.B., Colvin. T.S., and Ahuja, L.R., Prediction of NO3-N losses with subsurface drainage water from manured and UAN-fertilized plots using GLEAMS. Trans. ASAE. 43:69-77.2000.

 

110. Butters, G., Benjamin, J.C., Ahuja, L.R., and Ruan, H., Bromide and Altrazine leaching in furrow and sprinkler irrigated corn Soil Sci. Soc. Am. J. 64:1723-1732. 2000.

 

111. Cameira, M.R., Ahuja, L., Fernando, R.M. and Perreira, L.S., Evaluating field measured soil hydraulic properties in water transport simulations using RZWQM. J. Hydrol. 236:78-90. 2000.

 

112. Flerchinger, G.N., Aiken, R.M., Rojas, K.W., and Ahuja, L.R., Development of the Root Zone Water Quality Model (RZWQM) for over-winter conditions. Trans. ASAE. 43:59-68. 2000.

 

113. Ma, L., Ahuja, L.R., Ascough II, J.C., Shaffer, M.J., Rojas, K.W., Malone, R.W., and Cameira, M.R., Integrating system modeling with field research in agriculture: Applications of the Root Zone Water Quality Model (RZWQM). Advances in Agronomy. 71:233-292. 2000.

 

114. Ma, L., Ascough, J.C., Ahuja, L.R., Shaffer, M.H., Hanson, J.D., Rojas, K.W., and Hanson, J.D. Root Zone Water Quality Model sensitivity analysis using the Monte Carlo Simulation. Trans. ASAE. 43:883-895. 2000.

 

115. Bakhsh, A., Kanwar, R.S., Jaynes, D.B., Colvin, T.S., and Ahuja, L.R., Simulating effects of variable nitrogen application rates on yield and NO3-N losses in subsurface drain water. Trans. ASAE. 44(2):269-276. 2001.

 

116. Malone, R.W., Shipitalo, M.J., Ma, L., Ahuja, L.R., and Rojas, K.W.,

Macropore component assessment of the Root Zone Water Quality Model

(RZWQM) using no-till soil blocks. Trans. ASAE. 44:843-852. 2001.

 

117. Ruan, H., Ahuja, L.R., Green, T.R., and Benjamin, J.G., Residue cover and crusting effects on infiltration: numerical simulations for field applications. Soil Sci. Soc. Am. J. 65(3):853-861. 2001.

 

118. Fiedler, F.R., Frasier, G.W., Ramirez, J.A., and Ahuja, L.R., Hydrologic response of grasslands: effects of grazing, interactive infiltration, and scale. J. Hydrologic Engr. 7:203-301. 2002.

 

119. Heilman, P., Hatfield, J.L., Rojas, K.W., Ma, L., Huddleston, J., Ahuja, L.R., and Adkins, M., How good is good enough? What information is needed for agriculture and how can it be provided most affordably? J. Soil and Water Conserv. 57:98-105. 2002.

 

120. Mansell, R.S., Ma, L., Ahuja, L.R., and Bloom, S.A., Adaptive grid refinement in numerical models for water flow and solute transport in soil: A review. Vadose Zone J. 1:222-238. 2002.

 

121. McMaster, G.S., Ascough II, J.C., Dunn, G.H., Weltz, M.A., Shaffer, M.J., Palic, D., Vandenberg, B.C., Bartling, P.N.S., Edmunds, D., Hoag, D.L., and Ahuja, L.R. Application and testing of GPFARM: A farm and ranch decision support system for evaluating economic and environmental sustainability of agricultural enterprises. Acta Horticulturae 593:171-177. 2002.

 

122. Nielsen, D.C., Ma, L., Ahuja, L.R., and Hoogenboom, G., Simulating soybean water stress effects with RZWQM and CROPGRO models. Agron. J. 94:1234-1243. 2002.

 

123. Shaver, T.M., Peterson, G.A., Ahuja, L.R., Westfall, D.G., Sherrod, L.A., and Dunn, G.H., Surface soil physical properties after twelve years of dryland notill management. Soil Sci. Soc. Am. J. 66:1296-1303. 2002.

 

124. Ahuja, L.R., Quantifying agricultural management effects on soil properties and processes. Geoderma. 116:1-2. 2003.

 

125. Ahuja, L.R., Created Special Issue of Geoderma on Quantifying Agricultural Management Effects on Soil Properties and Processes. Geoderma. 116:1-248.

2003.

 

126. Aiken, R., Nielsen, D.C., and Ahuja, L.R., Scaling effects of standing crop residues on the wind profile. Agronomy J. 95:1041-1046. 2003.

 

127. Andales, A.A., Ahuja, L.R., and Peterson, G.A., Evaluation of GPFARM for dryland cropping systems in Eastern Colorado. Agronomy J. 95:1510-1524.

2003.

 

128. Green, T.R., Ahuja, L.R., and Benjamin, J.G., Advances and challenges in predicting agricultural management effects on soil hydraulic properties in space and time. Geoderma. 116(1-2):3-27. 2003.

 

129. Heathman, G.C., Starks, P.J., Ahuja, L.R., and Jackson, T.J., Assimilation of surface soil moisture to estimate profile soil water content. J. Hydrology 279:1-17. 2003.

 

130. Ma, L., Nielsen, D. C., Ahuja, L. R., Malone, R.M., Saseendran, S.A., Rojas, K.W., Hanson, J.D., and Benjamin, J.G., Evaluation of RZWQM under

varying irrigation levels in Eastern Colorado. Trans. ASAE. 46:39-49. 2003.

 

131. Malone, R.W., Logsdon, S., Shipitalo, M.J., Weatherington-Rice, J., Ahuja, L.R., and Ma, L., Tillage effect on macroporosity and herbicide transport in percolate. Geoderma 116:191-215. 2003.

 

132. Sherrod, L.A., Peterson, G.A., Westfall, D.G., and Ahuja, L.R., Cropping intensity enhances soil organic carbon and nitrogen in a no-till agroecosystem. Soil Sci. Soc. Am. J. 67:1533-1543. 2003.

 

133. Starks, P.J., Heathman, G.C., Ahuja, L.R., and Ma, L., Use of limited soil property data and modeling to estimate root zone soil water content. J. Hydrology. 272:131-147. 2003.

 

134. Wauchope, R.D., Ahuja, L.R., Arnold, J.G., Bingner, R., Lowrance, R., Van Genuchten, M.T., and Adams, L.D., Software for pest management science: Computer models and databases from the U.S. Department of Agriculture- Agricultural Research Service. Special Issue of Pest Management Sci. 59:691-698. 2003.

 

135. Bakhsh, A., Ma, L., Ahuja, L.R., Hatfield, J.L., and Kanwar, R.S., Using RZWQM to predict herbicide leaching losses in subsurface drainage water. Trans. ASAE. 47:1415-1426. 2004.

 

136. Bakhsh, A., Hatfield, J.L., Kanwar, R.S., Ma, L., and Ahuja, L.R., Simulating nitrate losses from a Walnut Creek Watershed field. J. Environ. Quality. 33:114-123. 2004.

 

137. Ma, Q., Rahman, A., James, T. K., Holland, P. T., McNaughton, D. E., Rojas,

K.W., and Ahuja, L. R., Modeling the fate of Acetochlor and terbuthylazine in the field using the Root Zone Water Quality Model. Soil Sci. Soc. Am. J. 68:1491-1500. 2004.

 

138. Ma, Q. L., Wauchope, R.D., Ma, L., Rojas, K.W., Malone, R.W., and Ahuja, L.R., Test of the Root Zone Water Quality Model (RZWQM) for predicting runoff of atrazine, alachlor and fenamiphos species from conventional-till corn mesoplots. Pest Management Sci. 60:267-276. 2004.

 

139. Ma, Q. L., Wauchope, R.D., Rojas, K.W., Ahuja, L.R., Ma, L., and Malone, R.W., The pesticide module of the Root Zone Water Quality Model (RZWQM): testing and sensitivity analysis of selected algorithms for pesticide fate and surface runoff. Pest Management Sci. 60:240-252. 2004.

 

140. Malone, R. W., Weatherington-Rice, J., Shipitalo, M., Fausey, N., Ma, L., Ahuja, L.R., Wauchope, R.D., and Ma, Q.L., Herbicide leaching as affected by macropore flow and within-storm rainfall intensity variation: a RZWQM simulation. Pest Management Sci. 60:277-285. 2004.

 

141. Malone, R.W., Ma, L., Wauchope, R. D., Ahuja, L. R., Rojas, K. W., Ma, Q. L., Warner, R., and Byers, M., Modeling hydrology, metribuzin degradation and metribuzin transport in macroporous tilled and no-till silt loam soil using RZWQM. Pest Management Sci. 60:253-266. 2004.

 

142. Malone, R.W., Ahuja, L. R., Ma, L., Wauchope, R. D., Ma, Q.L., and Rojas, K.W., Application of the Root Zone Water Quality Model (RZWQM) to pesticide fate and transport: an overview. Pest Management Sci. 60:205-221. 2004.

 

143. Saseendran, S.A., Nielsen, D.C., Ma, L., Ahuja, L.R., and Halvorson, A.D., Modeling nitrogen management effects on a winter wheat production using RZWQM and CERES-wheat. Agron. J. 96:615-630. 2004.

 

144. Wauchope, R.D., Rojas, K.W., Ahuja, L.R., Ma, Q.L., Malone, R.W., and Ma, L., Documenting the pesticide processes module of the ARS RZWQM Agro-ecosystem Model. Pest Management Sci. 60:222-239. 2004.

 

145. Ahuja, L.R., Ascough II, J.C., and David, O., Developing natural resource models using the Object Modeling System: feasibility and challenges. Advs. Geos. 4:29-36. 2005.

 

146. Andales, A.A., Derner, J.D., Bartling, P.N.S., Ahuja, L.R., Dunn, G.H., Hart, R.H., and Hanson, J.D., Evaluation of GPFARM for simulation of production and cow-calf weights. Rangeland Ecology and Management. 58:247-255. 2005.

 

147. Kozak, J.A., Ahuja, L.R., Ma, L., and Green, T.R., Scaling and estimation of evaporation and transpiration of water across soil texture classes. Vadose Zone J. 4:418-427. 2005.

 

148. Kozak, J.A., and Ahuja, L.R., Scaling of Infiltration and Redistribution of Water Across Soil Textural Classes. Soil Sci. Soc. Am. J. 69:816-827. 2005.

 

149. Ma, L., Hoogenboom, G., Ahuja, L.R., Nielsen, D. C., and Ascough II, J.C., Development and evaluation of RZWQM-CROPGRO hybrid model for soybean production. Agron. J. 97:1172-1182. 2005.

 

150. Saseendran, S.A., Nielsen, D.C., Ma, L., Ahuja, L.R., Vigil, M.F., Benjamin, J.G., and Halvorson, A.D., Effectiveness of RZWQM for simulating alternative Great Plains cropping systems. Agron. J. 97:1183-1193. 2005.

 

151. Saseendran, S.A., Ma, L., Nielsen, D.C., Vigil, M.F., and Ahuja, L.R., Simulating planting date effect on corn production using RZWQM and CERES-Maize models. Agronomy J. 97:58-71. 2005.

 

152. Sherrod, L.A., Peterson, G.A., Westfall, D.G., and Ahuja, L.R., Soil organic carbon pools after 12 years in no-till dryland agroecosystems. Soil Sci. Soc. Am. J. 69:1600-1608. 2005.

 

153. Cameira, M.R., Fernando, R.M., Ahuja, L.R., and Pereira, L., Simulating the fate of water in field soil-crop environment. J. Hydrology 315: 1-24. 2005.

 

154. Bakhsh, A., Kanwar, R.S., Jaynes, D.B., Colvin, T.S., and Ahuja, L.R. Modeling precision agriculture for better crop productivity and Environmental quality. International Agricultural Engineering Journal, 14(4):235-245. 2005.

 

155. Meng, H., Salas, J.D., Green, T.R., and Ahuja, L.R., Scaling analysis of space-time infiltration based on the universal multifractal model. J. Hydrology 322:220-235. 2006.

 

156. Chander, S., Ahuja, L.R., Peairs, F.B., Aggarwal, P.K., and Kalra, N., Simulating the effect of Russian wheat aphid, Diuraphis noxia (Mordvilko) and weeds in winter wheat. Agric. Systems. Agricultural Systems 88: 494-513. 2006.

 

157. Ma, L., Hoogenboom, G., Ahuja, L. R., Ascough II, J. C., and Saseendran, S. A., Evaluation of RZWQM-CERES-maize hybrid for maize production. Agric. Systems. 87: 274-295. 2006.

 

158. Hu, C., Saseendran, S.A., Green, T. R., Ma, L., Li, X., and Ahuja, L.R., Evaluating nitrogen and water management of a double cropping system in China. Vadose Zone J. 5: 493-505. 2006.

 

159. Ahuja, L.R., Ma, L., and Timlin, D.J., Trans-disciplinary soil physics research critical to synthesis and modeling of agricultural systems. Soil Sci. Soc. Am. J. 70: 311-326. 2006.

 

160. Yu, Q., Saseendran, S.A., Ma, L., Flerchinger, G.N., Green, T.R., and Ahuja, L.R., Modeling a wheat-maize double cropping system in China using two plant growth modules with RZWQM. Agric. Systems 89: 457-477. 2006.

 

161. Kozak, J.A., Ma, L., Ahuja, L.R., Flerchinger, G., and Nielsen, D.C. Evaluating various stress calculations in RZWQM and RZ-SHAW for corn and soybean production. Agronomy J. 98: 1146-1155. 2006.

 

162. Andales, A.A., Derner, J.D., Ahuja, L.R., and Hart, R.H. Strategic and Tactical prediction o forage production in Northern Mixed-Grass Prairie. Rangeland ecology and Management 59: 576-584. 2006.

 

163. Kozak, J.A., Ahuja, L.R., Green, T.R., and Ma, L., Modeling crop canopy and residue rainfall interception on soil hydrologic components for semi-arid agriculture. Hydrologic Processes 21: 229-241. 2007.

 

164. Ahuja, L.R., Andales, A.A., Ma, L., and Saseendran, S.A. Whole system integration and modeling essential to agricultural science and technology for the twenty-first century. J. Crop Improvement 19/1/2: 73-103. 2007.

 

165. Andales, A. A., Green, T.R., Ahuja, L.R., Erskine, R.H., and Peterson, G.A. Temporally stable patterns in grain yield and soil water on a dryland catena. Agricultural Systems: 94: 119-127. 2007.

 

166. Ma, L., Malone, R.W., Heilman, P., Jaynes, D. B., Ahuja, L. R., Saseendran, S. A., Kanwar, R. S., and Ascough, II. J. C. RZWQM Simulated Effects of Crop Rotation, Tillage, and Controlled Drainage on Crop Yield and nitrate-N Loss in Drain  Flow. Geoderma 140:297-309. 2007.

 

167. Ma, L., Malone, R.W., Heilman, P., Ahuja, L. R., Meade, T., Saseendran, S. A., Ascough, II, J.C., and Kanwar, R.S. Sensitivity of Tile Drainage Flow and Crop Field on Measured and Calibrated Soil Hydraulic Properties. Geoderma Geoderma.140:284-296. 2007.

 

168. Saseendran, S.A., Ma, L., Malone, R., Heilman,P., Ahuja, L.R., Kanwar, R.S., Karlen, D.L., and Hoogenboom, G. Simulating management effects on crop production, tile drainage, and water quality using RZWQM-DSSAT. Geoderma 140: 260-271. 2007.

 

169. Ma, L., Malone, R.W., Heilman, P., Karlen, D.L., Kanwar, R.S., Cambardella, C.A., Saseendran, S.A., and Ahuja, L.R. RZWQM simulation of long-term crop production, water and nitrogen balances in Northwest Iowa. Geoderma 140: 247-259. 2007.

 

170. Ahuja, L.R. and Hatfield, J.L. Quantifying management effects in long-term field studies using system models: Purpose and overview of the Special Issue. Geoderma 140: 217-222. 2007.

 

171. Yu, Q., Flerchinger, G. N., S. Xu, Kozak, J., Ma, L., and Ahuja, L. R. 2007. Energy Balance Simulation of a wheat canopy using RZ-SHAW Model. Trans. ASABE. 50:1507-1516. 2007.

 

172. Cameira, M. R., Fernando, R. M., Ahuja, L. R., and Ma, L. 2007. Using RZWQM to Simulate the Fate of Nitrogen in Field Soil – Crop Environment in the Mediterranean Region. Agricultural Water Management 90: 121-136. 2007.

 

173. Kozak, J. A., Aiken, R., Flerchinger, G. N., Nielsen, D. C., Ma, L., and Ahuja L. R. Quantifying Residue Architecture Effects on Soil Temperature and Water. Soil and Tillage Research 95: 84-90. 2007.

 

174. Ahuja, L. R., Kozak, J. A., Andales, A. A., and Ma, L. Scaling parameters of the Lewis-Kostiakov ponded-water infiltration equation across soil texture classes. Trans. ASABE. 50:1525-1541. 2007.

 

175. Ma, L., Ahuja, L. R., and Malone, R.W. Systems modeling for soil and water research and management: current status and further needs in the 21st century. Trans. of the ASABE. 50:1705-1713. 2007.

 

176. Meng, H., Green, T.R., Salas, J.D., and Ahuja, L.R. Development and testing of a terrain-based hydrologic model for spatial Hortonian infiltration and runoff/ on. Environmental Modeling and Software: 23(6), 794-812. 2008.

 

177. Li, L. Malone, R.W., Ma, L., Kaspar, T.C., Jaynes, D.B., Saseendran, S.A., Yu, Q., and Ahuja, L. R. Winter cover crop effects on nitrate leaching in subsurface drainage as simulated by RZWQM-DSSAT. Trans. of the ASABE 51(5):1575-1583. 2008.

 

178. Saseendran, S. A., L.R. Ahuja, D. C. Nielsen, L. R., Trout, T., and Ma, L. Use of crop simulation models to evaluate limited irrigation management options for corn in a semiarid environment. Water Resources Research. 44, W00E02, doi:10.1029/2007WR006181. 2008.

 

179. Ma, L., Malone, R.W., Jaynes, D.B., Thorp, K., and Ahuja. L. R. Simulated Effects of Nitrogen Management and Soil Microbes on Soil N Balance and Crop Production. SSSAJ. 72:1594-1603. 2008.

 

180. Fang, Q., Ma, L., Yu,Q., Malone, R. W., Saseendran, S. A., and Ahuja, L. R. Modeling nitrogen and water management effects in a wheat-maize double-cropping system. Journal of Environmental Quality 37:2232-2242. 2008.

 

181. Green, T.R., Dunn, G.H., Erskine, R.H., Salas, J.D., and Ahuja. L.R. Fractal analyses of steady infiltration and terrain on an undulating agricultural field. Vadose Zone Journal: 8(2) 310-320. 2009.

 

182. Ma, L., Hoogenboom, G., Saseendran, S.A., Bartling, P.N., L.R., Ahuja, and

Green, T.R. Effects of estimating soil hydraulic properties and root growth

factor on soil water balance and crop production. Agronomy Journal: 101(3),

572-583. 2009.

 

183. Saseendran, S.A., Nielsen, D.C., Lyon, D.J., Ma, L., Felter, D.G., Baltensperger, D.D., Hoogenboom, G., and Ahuja. L.R. Modeling responses of dryland spring tritcale, proso millet, and foxtail millet to initial soil water in the High Plains. Field Crops Research: 113(1), 48-63. 2009.

 

184. Fang, Q., Ma, L., Green, T.R., Yu, Q., Wang, T.D., and Ahuja. L.R. Water resources and agricultural water use in the North China Plain: Current status and management options. Agricultural Water Management 97(8):1102-1116. 2010.

 

185. Fang, Q., Ma, L., Yu, Q., Ahuja, L.R., Malone, R.W., and Hoogenboom. G. Irrigation strategies to improve water use efficiency in the wheat-maize double cropping system in China. Agricultural Water Management 97(8): 1165-1174. 2010.

 

186. Li, L., Nielsen, D. C., Yu, Q., Ma, L., and Ahuja, L. R. Seasonal variations of CWSI and its correlation with soil moisture, CO2 flux, and canopy water use efficiency in the North China Plain. Agricultural Water Management 97(8): 1146-1155. 2010.

 

187. Ascough, II, J.C., Andales, A.A., Sherrod, L.A., McMaster, G.S., Hansen, N.C., Dejonge, K.C., Fathelrahman, E.M., Ahuja, L.R., Peterson, G.A., and Hoag, D.L. Simulating landscape catena effects in no-till dryland agroecosystems using GPFARM. Agricultural Systems. 103(8):569-584. 2010.

 

188. Fang, Q.X., Green, T.R., Ma, L., Malone, R.W., Erskine, R.H., and Ahuja, L.R. Optimizing soil hydraulic parameters in RZWQM2 using automated calibration methods. SSSAJ. 74:1897-1913. 2010.

 

189. Saseendran, S.A., Nielsen, D. C., Ma, L., and Ahuja, L.R. Adapting CROPGRO for simulating spring canola growth with both RZWQM2 and DSSAT 4.0. Agronomy J. 102:1606-1621. 2010.

 

190. Saseendran, S.A., Nielsen, D.C., Ma, L., Ahuja, L.R., and Vigil, M.F. Simulating alternative dryland rotational cropping systems in the Central Great Plains with RZWQM2. Agronomy Journal. 102:1521-1534. 2010.

 

191. Ahuja, L.R., Ma, L., and Green, T.R. Effective properties of heterogeneous areas. Soil Sci. Soc. Am. J. 74:1469-1482. 2010.

 

192. Ko, J., Ahuja, L. R., Kimball, B., Saseendran, S. A., Ma, L., Green, T. R., Wall, G., and Pinter, P. Simulation of free air CO2 enriched wheat growth and interactions with water, nitrogen, and temperature. Agriculture and Forest Meteorology. 150:1331-1346. 2010.

 

193. Adiku, S.G.K., Dunn, G.H., Ahuja, L.R., Gunter, S.A., Bradford, J.A., Garcia,L., and Andales, A.A. Simulation of sandsage-bluestem forage growth under varying stocking rates. Rangeland Ecology and Management. 63: 546- 552. 2010.

 

194. Lloyd, W., David, O., Ascough II, J.C., Rojas, K.W., Carlson, J.R., Leavesley, G.H., Krause, P., Green, T.R., and Ahuja, L.R. Environmental modeling framework invasiveness: Analysis and implications. Environmental Modeling and Software 26: 1240-1250. 2011.

 

195. Jury, W.A., Or, D., Pachepsky, Y., Vereecken, H., Hopmans, J.W., Ahuja, L.R., Clothier, B.E., Bristow, K.L., Kluitenberg, G.J., Moldrup, P., Simunek, J., van Genuchten, M. Th., Horton, R. Kirkham’s legacy and contemporary challenges in soil physics research. Soil Sci. Am. J. 75: 1589-1601. 2011.

 

196. Ma, L., Trout, T., Ahuja, L.R., Bausch, W., Saseendran, S.A., Malone, R.W., Nielsen, D.C. Calibrating RZWQM2 model for maize responses to deficit irrigation. Agric. Water Manage. 103: 140-149. 2012.

 

197. Ko, J., Ahuja, L. R., Saseendran, S. A., Green, T. R., Ma, L., Nielsen, D. C., and Walthall, C. Climate change impacts on dryland cropping systems in the central Great Plains, USA. Climatic Change 111: 445-472. 2012.

 

198. Fang, Q. X., Malone, R. W., Ma, L., Jaynes, D. B., Green, T. R., and Ahuja, L. R. Modeling the effect of controlled drainage, N rate, and weather on nitrate loss to subsurface drainage. Agric. Water Manage. 103:150-161. 2012.

 

199.Heilman, P., Malone, R.W., Ma, L., Hatfield, J.L., Ahuja, L.R., Boyle, K.P., and Kanwar, R.S. Extending the results from agricultural fields with intensively monitored data to surrounding areas for water quality management. Agric. Systems 106: 59-71. 2012.

 

200. Qi, Z., Ma, L., Helmers, M. J., Ahuja, L. R., and Malone, R. W. Simulating  nitratenitrogen concentration from a subsurface drainage system in response to nitrogen application rates using RZWQM2. J. Environ. Qual. 41: 289-295. 2012.

 

201. Qi, Z., Bartling, P.N.S., Ahuja, L.R., Derner, J.D., Dunn, G.H., Ma, L.  Development and evaluation of the carbon-nitrogen cycle modules for the GPFARM-Range model. J. Computers and Electronics. 83: 1-10. 2012.

 

202. Ma, L., Flerchinger, G. N., Ahuja, L. R., Sauer, T., Prueger, J. H., Malone, R. W., and Hatfield, J. L. Simulation of the surface energy balances in a soybean canopy using SHAW and RZ-SHAW. Trans. ASABE. Accepted Dec. 5, 2011.

 

203. Ascough II, J.C., O. David, P. Krause, G.C. Heathman, S. Kralisch, M. Larose, L.R. Ahuja. 2012. Development and application of a modular watershed-scale hydrologic model using the Object Modeling System: runoff response evaluation. Trans. ASABE. Accepted Jan. 31, 2011.

 

204. Sherrod, L.A., Reeder, J.D., Hunter, W., Ahuja, L.R. A rapid and cost effective method for soil carbon mineralization in static laboratory incubations. Communications in Soil and Plant Analysis. Accepted Feb. 14, 2012.

 

Additional Publications

 

205. Ahuja, L.R., Response of hybrid maize to micro-nutrients. Indian Agric. Res. Inst. 113pp. 1961. (Thesis)

 

206. Ahuja, L.R., Radial flow of soil water to a cylindrical sink - (Dissertation). Univ. of California. Dissert. Abstr. #69-16. 127pp. 1968. (Thesis)

 

207. Ahuja. L.R., and El-Swaify, S.A. Hydrologic characteristics of benchmark soils of Hawaii's forest watersheds. Final Project Report, Univ. of Hawaii-USDA, Forest Service Cooperative Agreement #21-190. 155p. 1975. (Technical Research Report)

 

208. Ahuja, L.R., and Green, R.E., Simplified techniques for determining water conducting and water storage properties of soils. Water Resources Res. Center, Univ. of Hawaii. Tech. Memo Rept. #40. 33pp. 1976. (Technical Research Report)

 

209. Dangler, E.W., El-Swaify, S.A., Ahuja, L.R., and Barnett, A.P., Erodibility of selected Hawaii soils by rainfall simulation. ARS W-35, USDA-ARS. 113pp. 1976. (Technical Research Report)

 

210. El-Swaify, S.A., and Ahuja, L.R., Quality trends of waters from various sources at the University of Hawaii Lyon Arboretum for the calendar year 1974. Hawaii Agric. Exp. Stn. Paper #39. 10pp. 1976. (Technical Research Report)

 

211. Ahuja, L.R., Green, R.E., and Lau, L.S., Characterizing water conducting and water storage properties of soils from minimum field data. Project Bull. #12. Water Resources Res. Center, Univ. of Hawaii. 2p. 1978. (Bulletin)

 

212. Naney, J.W., and Ahuja, L.R. A simple method to characterize watershed soils. Proc. ASCE Watershed Management Symp. Bose, ID. July 21-23, Am. Soc. Civ. Engineering. pp. 731-742. 1980. (Proceedings)

 

213. Ahuja, L.R., Sharpley, A.N., Menzel, R.G., and Smith, S.J., Modeling the release of phosphorus and related adsorbed chemicals from soil to overland flow. In  Modeling Components of Hydrologic Cycle. Water Resources Pub., CO. pp. 463-484. 1982. (Book Chapter)

 

214. Green, R.E., Ahuja, L.R., Chong, S.K., and Lau, L.S., Water conduction in Hawaii toxic soils. Water Resources Res. Center, Univ. of Hawaii. Tech. Rept. #143. 122pp. 1982. (Technical Research Report)

 

215. Ahuja, L.R., and Ross, J.D. A new Green-Ampt type model for infiltration through a surface seal permitting transient parameters below the seal. Proceedings of the National Conference on Advances in Infiltration. ASAE Public. 11-83:147-182. 1983. (Proceedings)

 

216. Ahuja, L.R., and Williams, R.D. Use of a surface gamma-neutron gauge to measure bulk density, field capacity, and macroporosity in the topsoil. IAEA/FAO International Symposium on Isotope and Radiation Techniques in Soil Physics and Irrigation Studies. Aix-en-Provence, France. April 18-22, 1983. pp. 469-478. 1983. (Extended Synopsis)

 

217. Naney, J.W., Ahuja, L.R., and Barnes, B.B. Variability and interrelation of soil-water and related soil properties in a small watershed. Proc. of the National Conference on Advances in Infiltration. ASAE Public. 11-83:92-101. 1983. (Proceedings)

218. Ahuja, L.R., and Ross, J.D. A Green-Ampt type model for infiltration through a surface seal. Proc. Natural Resources Modeling Symposium, D.G. DeCoursey (ed.), ARS-30:345-348. 1985. (Proceedings)

 

219. Naney, J.W., and Ahuja, L.R. Characterization of variable soil water properties. Proc. Symp. Watershed Management, Irrig. and Drain. Div., ASCE. Denver, CO. April 30-May 1, 1985. pp. 285-292. 2005. (Proceedings)

 

220. Sharpley, A.N., Ahuja, L.R., and Pionke, H.B. The role of desorption kinetics in modeling transport of phosphorus and related adsorbed chemicals in runoff. Proc. Natural Resources Modeling Symposium. D.G. DeCoursey (ed.), ARS-30:155-159. 1985. (Proceedings)

 

221. Williams, R.D., Naney, J.W., and Ahuja, L.R. Soil properties and productivity changes along a slope. Erosion and Soil Productivity. Proc. Nat. Symp. on Erosion and Soil Productivity, ASAE Public. 8-85:96-106. 1985. (Proceedings)

 

222. Green, R.E., Ahuja, L.R., and She-Kong, S.K., Unsaturated hydraulic conductivity, soil water diffusivity, and sorptivity: field methods. In Methods of Soil Analysis, Part I, Klute, A. (ed.), American Society of Agronomy. Monograph #9. pp. 771-798. 1986. (Book Chapter)

 

223. Ahuja, L.R. Research needs for unsaturated zone transport modeling of agricultural chemicals: Flow processes. Proc. Workshop Res. Needs Unsat. Zone Transp. Modeling Agric. Chem. Nov. 2-4, Annapolis, M.D. Agric. Res. Inst., Bethesda, MD. pp. 83-91. 1987. (Proceedings)

 

224. Ahuja, L.R., Lehman, O.R., and Heathman, G.C. Transport of chemicals in runoff from partial land-area applications. Proc. Intern. Conf. Infiltration Develop. Applications. Yu-Si Fok (ed.), University of Hawaii, Honolulu. pp. 475-483. 1987. (Proceedings)

 

225. Lehman, O.R., Ahuja, L.R., and Heathman, G.C. The transfer of  surfaceapplied chemicals to runoff as influenced by soil slope length. Am. Soc.

Agric. Egn. Paper #87-2626. ASAE Winter Meeting. Dec. 1987, Chicago, IL. 1987. (Proceedings)

 

226. Ahuja, L.R., Martin, D.L., and Barnes, B.B. Modeling to improve soilwater-chemical management using easily measured soil properties. In P.W. Unger et.al. (ed.), Proc. Intern. Conf. Dryland Farming. Amarillo/Bushland, TX, Aug. 15-18. USDA-ARS, Bushland, TX. pp. 697-699. 1988. (Proceedings)

 

227. Ahuja, L.R., Bruce, R.R., Cassel, D.K., and Rawls, W.J. Simpler field measurement and estimation of soil hydraulic properties and their spatial variability for modeling. Proc. Intern. Symp. Modeling Agric., Forest and Rangeland Hydrology. Dec. 12-13. Chicago, IL. ASAE Public. 07-88:142-153. 1988. (Proceedings)

228. Sharpley, A.N., Ahuja, L.R., and Smith, S.J. Chemical transport in agricultural runoff: model improvement and application. Proc. Intern. Symp. Modeling Agric., Forest and Rangeland Hydrol. Dec. 12-13. ASAE Pub. 07-88:142-155.1988. (Proceedings)

 

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229. Ahuja, L.R., Martin, D.L., and Smith, S.J. Modeling for best management of water and nutrients in sandy soils. Intern. Symp. Managing Sandy Soils. Feb. 6-10. Central Arid Zone Research Institute, Jodhpur, India. Proc. Part I: 398-401. 1989. (Proceedings)

 

230. Gupta, R.P., and Ahuja, L.R. Unsaturated hydraulic conductivity and soil water diffusivity. Proc. Intern. Workshop on Methodology for Rice Physical Measurements. Oct. 24-28. IARI-IRRI, New Delhi. 1989. (Proceedings)

 

231. Ahuja, L.R., and Nielsen, D.R., Field soil-water relations. In B.A. Stewart, and Nielsen, D.R., (eds.). Irrigation of Agricultural Crops. Agronomy Monograph 30. Amer. Soc. Agronomy. pp. 143-190. 1990. (Book Chapter)

 

232. Sharpley, A.N., Ahuja, L.R., and Smith, S.J., Modeling the transport of phosphorus and related chemicals: a kinetic approach. Small Watershed Model. (SWAM) for Water, Sediment and Chemical Movement. ARS-80:118-133. 1990. (Book Chapter)

 

233. Sharpley, A.N., Smith, S.J., Ahuja, L.R., and Heathman, G.C. Prediction of chemical transport in agricultural runoff: an integrated modeling approach. Proc. Intern. Symp. Water Qual. Modeling Agric. Nonpoint Sources, Part 2. ARS-81:875-881. 1990. (Proceedings)

 

234. Ahuja, L.R., DeCoursey, D.G., Barnes, B.B., and Rojas, K.W. Characteristics and importance of preferential macropore transport studied with the ARS Root Zone Water Quality Model. Proc. Nat. Symp. Preferential Flow. Chicago, IL, Dec. 16-17. ASAE Public. pp. 32-49. 1991. (Proceedings)

 

235. Ahuja, L.R., Rojas, K.W., and Johnsen, K.E. Modeling the behavior of fertilizers and pesticides in relation to chemigation. Proc. FAO Expert Consultation on Fertigation/Chemigation. Cairo, Egypt, Sept. 8-11. UNFAO, Rome. 1991. (Technical Report)

 

236. Ahuja, L.R., Timlin, D.J., and Heathman, G.C. Modeling soluble chemical transfer from soil to overland flow and its transport through macropores to groundwater. Proc. Intern. Symp., Hydrologic Basis of Ecologically Sound Management of Soil and Groundwater. Aug. 11-26. IAHS Public. 202:3-11.1991. (Proceedings)

 

237. Ahuja, L.R., and Hebson, C.S., Water, chemical and heat transport in soil matrix and macropores (chapter 1). In Root Zone Water Quality Model, Version 1.0, Technical Documentation. GPSR Tech. Report No. 2. USDAARS- GPSR, Fort Collins, CO. p.1-26. 1992. (Book Chapter)

 

238. Naney, J.W., Ahuja, L.R., Williams, R.D., and Rawls, W.J. Estimating spatial distribution of hydraulic conductivity in a field using effective porosity data. Proc. Intern. Workshop on Indirect Methods for Estimating Hydraulic Properties of Unsaturated Soils. Univ. of California, Riverside, CA. Oct. 11-13, 1989. pp. 515-524. 1992. (Proceedings)

 

239. Rawls, W.J., Ahuja, L.R., and Brakensiek, D.L. Estimating soil hydraulic properties from soil data. Proc. Intern. Workshop on Indirect Methods for Estimating Hydraulic Properties of Unsaturated Soils. Univ. of California, Riverside, CA. Oct. 11-13, 1989. pp. 329-340, 1992. (Proceedings).

 

240. RZWQM Team, The Root Zone Water Quality Model, Version 1.0, Technical Documentation. GPSR Tech. Rept. No. 2. USDA-ARS, Great Plains Systems Research Unit, Fort Collins, CO. 236pp.1992. L.R. Ahuja was Team Leader and major Contributor. (Technical Report).

 

241. RZWQM Team, The Root Zone Water Quality Model: User's Manual, GPSR Tech. Rept. No. 3. USDA-ARS, Great Plains Systems Research Unit, Fort Collins, CO. 103pp .1992. L.R. Ahuja was Team Leader and major Contributor. (Technical Report).

 

242. Williams, R.D., and Ahuja, L.R. Estimating soil water characteristics using easily measured physical properties and limited data. in Proc. Intern. Workshop on Indirect Methods for Estimating Hydraulic Properties of Unsaturated Soils.  University of California, Riverside, CA. Oct.11-13, 1989. pp. 405-416. (Proceedings). 1992. (Proceedings)

 

243. Ma, Q.L., Ahuja, L.R., and the RZWQM Team. Integrated-systems modeling of the effects of management on water quality: The Root Zone Water Quality Model (RZWQM). Proc. Conf. on Mgmt. Res. to Protect Water Quality. Feb 21-24, Minneapolis, MN. pp. 367-369. 1993. (Proceedings)

 

244. Rawls, W.J., Ahuja, L.R., Brakensiek, D.L., and Shirmohammadi, A., Infiltration and soil water movement. Chap. 5 in Maidment, (ed.) Handbook of Hydrology. McGraw-Hill Publishers: New York, p.5.1-5.51.1993. (Book Chapter)

 

245. Rojas, K.W., Ahuja, L.R., and Ma, Q.L. and four other team members. RZWQM to model management effects on water quality. Proc. Fed. Interagency Workshop Hydrology Modeling Demands for the 90s. June 7-9. Fort Collins, CO. USGS Water Resources Rept. 93-4018. pp. 5-1 to 5-7. 1993. (Proceedings)

 

246. Ahuja, L.R., Leppert, J.A., Rojas, K.W., and Seely, E. (Created by inviting authors and editors). Workshop on computer applications in water management. Proc. of the Workshop, May 23-25, 1995, Fort Collins, CO. GPAC Public. 154, Water Resources Res. Inst. Inform. Series 79. Colorado State Univ., Fort Collins, CO. 292pp. 1995. (Book).

 

247. Ascough II, J.C., Hanson, J.D., Shaffer, M.J., Buchleiter, G.W., Bartling, P.N., Vandenberg, B.C., Edmunds, D.A., Wiles, L., McMaster, G.S., and Ahuja, L.R. The GPFARM decision support system for whole farm/ranch management. Proc. Workshop on Computer Applications in Water Management; Great Plains, Agricultural Council Public. 154. Fort Collins, CO. pp 53-56. 1995. (Proceedings)

 

248. Buchleiter, G.W., Farahani, H.J., and Ahuja, L.R. Model evaluation of ground water contamination under center pivot irrigated corn in eastern Colorado. Proc. International Symposium on Water Quality Modeling. ASAE Pub. 595. Apr. 2-5. Kissimmee, FL. pp. 41-50. 1995. (Proceedings)

 

249. Farahani, H.J., Ahuja, L.R., Peterson, G.A., and Sherrod, L.A. Root Zone Water Quality Model evaluation of dryland/no-till crop production in eastern Colorado. Proc. International Symposium on Water Quality Modeling. ASAE Pub. 595. Kissimmee, FL. pp.11-20. 1995. (Proceedings)

 

250. Farahani, H.J., Ahuja, L.R., Peterson, G.A., Buchleiter, G.W., and Sherrod, L.A. Modeling of dryland and irrigated corn production systems in eastern Colorado. Proc. Workshop on Computer Applications in Water Management. Fort Collins, CO. Great Plains Agricultural Council. Public.154. Fort Collins, CO. pp. 78-81. 1995. (Proceedings)

 

251. Farahani, H.J., Ahuja, L.R., Buchleiter, G.W., and Peterson, G.A. Mathematical modeling of irrigated and dryland corn production in eastern Colorado. Proc. of the Clean Water-Clean Environment-21st Century. Kansas City, MO. ASAE Pub. 395. pp. 97-100. 1995. (Proceedings)

 

252. Mattakali, N.M., Engman, E.T., Ahuja, L.R., and Jackson, T.J. Estimating soil properties from microwave measurements of soil moisture. Proc. Conf. on Remote Sensing for Agriculture, Forestry, and Natural Resources. Sept. 26-28. Paris, France. pp. 89-101. 1995. (Proceedings)

 

253. Singh, P., Johnsen, K.E., Kanwar, R.S., and Ahuja, L.R. Simulating the effects of soil types on subsurface drain flows using RZWQM. Proc. International Symposium on Water Quality Modeling. Kissimmee, FL. ASAE Pub. 595. pp. 406-415. 1995. (Proceedings)

 

254. Ahuja, L.R., and Garrison, A. (Created by inviting authors and editors). Real World Infiltration. Proc. USDA-ARS Workshop, July 22-26, 1996, Pingree Park, CO. CO Water Resources Res. Inst. Inform. Series 86, Colorado State Univ., Fort Collins, CO. 262pp.1996. (Book)

 

255. Cameira, M.R., Sousa, P.L., Farahani, H.J., Ahuja, L.R., and Pereira, L.S. Simulation of water and nitrates in level basin fertigated maize using RZWQM model. Proc. Workshop Irrig. Drainage. Sept. 17. Cairo. pp 42-53. 1996. (Proceedings)

 

256. Farahani, H.J., Bausch, W.C., Aiken, R.M., and Ahuja. L.R. Evapotranspiration in System-Wide Models. Proceedings of the International ET and Irrigation Scheduling Symp. San Antonio, TX. ASAE. pp. 673-678. 1996. (Proceedings)

 

257. Logsdon, S.D., Nachabe, M.H., and Ahuja, L.R. Macropore modeling: state of science. In Proc. ARS Workshop on Real World Infiltration. CO Water 51 Resources Res. Inst. Information Series #87. pp.217-227. 1996. (Proceedings)

 

258. Mattakali, N.M., Engman, E.T., Ahuja, L.R., Johnsen, K.E., and Jackson, T.J., Spatial variability of saturated soil hydraulic conductivity derived from remotely-sensed data. In J.B. Stewart, (ed.), Scaling Up in Hydrology Using Remote Sensing, John Wiley: NY. pp.193-205. 1996. (Book Chapter)

 

259. Timlin, D.J., Williams, R.D., and Ahuja, L.R., Methods to estimate soil hydraulic parameters for regional scale application of mechanistic models. In D.L. Corwin and K. Loague (eds.), Application of GIS to the modeling of non-point source pollutants in the vedose zone, SSSA Pub. 48. Soil Science Society of America Madison, WI. pp 186-206.1996. (Book Chapter)

 

260. Timlin, D.J., Rawls, W.J., Williams, R., and Ahuja, L.R. Indirect estimation of hydraulic conductivity and its spatial distribution. Proc. ARS Workshop on Real World Infiltration. CO Water Resources Res. Inst. Information Series #87. pp.76-90. 1996. (Proceedings)

 

261. Williams, R.D., Ahuja, L.R., and Timlin, D.J. Estimating the soil water retention curve with soil bulk density and -33 kPa value. Proc. ARS Workshop on Real World Infiltration. CO Water Resources Res. Inst. Series #87. pp 91-101. 1996. (Proceedings)

 

262. Aiken, R.M., Nielsen, D.C., Vigil, M.F., and Ahuja, L.R. Field evaluation of energy balance simulation of surface soil temperatures. Proc. Int. Wind Erosion Symp. June 3-5. USDA-ARS, Manhattan, KS. 1997. (Proceedings)

 

263. Ahuja, L.R., Ma, L., Hanson, J.D. and Kanwar, R.S., Application of the root zone water quality model for environment-water management in agricultural systems. In L.S. Pereira, and Gowing, J.W., (eds.). Water and the Environment: Innovative Issues in Irrigation and Drainage, E&FN Spon: London. pp.3-11. 1998. (Book Chapter)

 

264. Ascough, J.C., McMaster, G.S., Shaffer, M.J., Hanson, J.D., and Ahuja, L.R. Economic and environmental strategic planning for the whole farm and ranch: The GPFARM decision support system. Proc.1st Interagency Hydrolog. Modeling Conference. Las Vegas, NV. April 19-23. USGS. Vol. 1:127- 1998. (Proceedings)

 

265. Bakhsh, A., Kanwar, R.S., and Ahuja, L.R. Simulating the Effects of Manure Application on Water Quality Using RZWQM. Proc. of the Conference on Animal Production System and the Environment: An International Conference on Odor, Water Quality, Nutrient Management and Socioeconomic Issues. July 19-22. Des Moines, Iowa. Vol. 1:445-456. 1998. (Proceedings)

 

266. Ma, L., Ahuja, L.R., Shaffer, M.J., Hanson, J.D., and Rojas, K.W. Parameterization, calibration, and sensitivity analysis of the RZWQM: A Synthesis. 1998 ASAE annual international meeting. Orlando, Florida, July 12-16. Paper No. 982214. 1998. (Proceedings)

 

267. Nachabe, M., Ahuja, L.R., Shaffer, M., Ascough, J., Flynn, B., and Cipra, J. Precision agriculture in dryland: spatial variability of crop yield and roles of soil surveys, aerial photos, and digital elevation models. Part of EUROPTA Conference on Remote Sensing for Agriculture, Ecosystems, and Hydrology. Barcelona, Spain. SPIE Vol. 3499:443-444. 1998. (Proceedings)

 

268. Peterson, G.A., Westfall, D.G., Sherrod, L., Poss, D., Larson, K., Thompson, D. and Ahuja, L.R., Sustainable dryland agroecosystem management. TB98-1. Agric. Exp. Stn., Colorado State University. Fort Collins, CO. 1998. (Technical Report)

 

269. Ahuja, L.R., Rawls, W.J., Nielsen, D.R. and Williams, R.D., Determining soil hydraulic properties and their field variability from simple measurements. Chap. 38, Agricultural Drainage. Am. Soc. Agronomy, Madison, WI. pp. 1185-1121. 1999. (Book Chapter)

 

270. Ascough II, J.C., Green, T.R. Ruan, H., and Ahuja, L.R. Scaling methods for Hydrological Ecosystems: A Review. Proc. Am. Soc. Agric. Eng./Can. Soc. Agric. Eng. 1999 Annual International Meeting, Paper No. 99-2001. July 18-22 Toronto, Canada. 1999. (Proceedings)

 

271. Bakhsh, A., Kanwar, R.S., Jaynes, D.B., Colvin, T.S., and Ahuja. L.R. Simulating the impacts of precision farming and variable N fertilizer rates on NO3-N losses and crop yield using RZWQM. in Mini-Conference on Adv. In Water Quality Modeling. ASAE Intern. Mtg. Toronto, Canada. pp. 127-132. 1999. (Proceedings)

 

272. Green, T.R., Nachabe, M.H., Ahuja, L.R., Murphy, M.R., Ascough II, J.C., and Shaffer, M.J. Preliminary Fractal Analysis of Crop Yield and Experimental Design and Modeling Space-Time Variability Under Dryland Agriculture. In H.J. Morel-Seytoux, (ed.) Proc. Nineteenth Annual AGU Hydrology Days. Aug. 16-20. Fort Collins, CO. pp. 187-198. 1999. (Proceedings)

 

273. Malone, R.W., M, L., Ahuja, L.R., and Rojas, K.W. Validation of the Root Zone Water Quality Model (RZWQM): A Review. Am. Soc. Agricultural Engr. Intern. Mtg, July 18-22. Paper No. 992145. 1999. (Proceedings)

 

274. Peterson, G.A., Westfall, D.G., Peairs, F.B., Sherrod, L., Poss, D., Gangloff, W., Larson, K., Thompson, D.L., Ahuja, L.R., Koch, M.D. and Walker, C.B., Sustainable dryland agroecosystem management. Colorado State Univ. TB99-1. 1999. (Technical Report)

 

275. Timlin, D.J., Ahuja, L.R., Pechepsky, Ya, Williams, R.D., Gimenez, D. and Rawls, W.J. Use of Brooks-Corey pore size distribution index to estimate saturated conductivity from effective porosity. Proc. Intern. Workshop Characterization and Measurement of the Hydraulic Properties of unsaturated Porosity Media, Oct. 22-24. Riverside, CA. M. Th. Van Genuchten, F.J. Leij, and L. Wu (eds.) Univ. Calif., Riverside. pp. 1029-1036. 1999. (Proceedings)

 

276. Williams, R.D., Ahuja, L.R. and Rawls, W.J. Estimating soil water retention using the Gregson one-parameter function. In: Van Genuchten, M. Th., Leij, F.J., and Wu, L. (eds.). Proc. Intern. Workshop Characterization and Measurement of the Hydraulic Properties of Unsaturated Porous Media, Oct. 22-24, 1997, Riverside, CA. Univ. Calif., Riverside. pp. 1011-1018. 1999. (Proceedings)

 

277. Ahuja, L.R., Hanson, J.D., Rojas, K.W. and Shaffer, M.J., Model Overview, In L.R. Ahuja, Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L. (eds.). Root Zone Water Quality Model. Water Resources Publication. Englewood, CO. pp 1-15. 1999. (Book Chapter)

 

278. Ahuja L.R., Benjamin, J.G., Dunn, G.H., Ma, L., Green, T.R., and Peterson, G.A. Quantifying wheel-track effects on soil hydraulic properties for agricultural systems modeling. Proc. 4th Intl. Conf. on Soil Dynamics. Univ. South Australia. Adelaide, Australia. pp 26-30. 2000. (Proceedings)

 

279. Ahuja, L.R., Johnsen, K.E. and Rojas, K.W., Water and chemical transport in soil matrix and macropores, In L.R. Ahuja, Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L. (eds.). Root Zone Water Quality Model. Water Resources Publication. Englewood, CO. pp 13-50. 2000. (Book Chapter)

 

280. Ahuja, L.R., Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L. (eds.) Root Zone Water Quality Model. Water Resources Publication, Englewood, CO. 372pp. 2000. (Book)

 

281. Hanson, J.D., Shaffer, M.J. and Ahuja, L.R., Simulating rangeland production and carbon sequestration. In R.F. Follett, Kimble, J.M., and Lal, R., (eds.) Carbon Sequestration Potential of U.S. Grazing Lands. Lewis Publishers, Boca Raton. pp 345-370. 2000. (Book Chapter)

 

282. Flerchinger, G.N., Aiken, R.M., Rojas, K.W., Ahuja, L.R., Johnsen, K. and Alonso, C.V., Soil heat transport, soil freezing, and snowpack conditions. In

L.R. Ahuja, Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L., (eds.). Root Zone Water Quality Model. Water Resources Publications. Englewood, CO. pp 281-314. 2000. (Book Chapter)

 

283. Peterson, G.A., Westfall, D.G., Peairs, F.B., Sherrod, L., Poss, D., Gangloff, W., Larson, K., Thompson, D.L., Ahuja, L.R., Koch, M.D., and Walker, C.B. Sustainable dryland agroecosystem management. Colorado State Univ. TB00-3. 2000. (Technical Bulletin)

 

284. Rojas, K.W. and Ahuja, L.R., Management Practices. In Ahuja, L.R., Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L. (eds.) Root Zone Water Quality Model. Water Resources Public. Englewood, CO. pp. 245-280. 2000. (Book Chapter)

 

285. Rojas, K.W., Ma, L. and Ahuja, L.R., RZWQM98 User Guide-Appendix, Root Zone Water Quality Model. In L.R. Ahuja, Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L. (eds.) Root Zone Water Quality Model. Water Resources Publications LLC. Englewood, CO. pp. 327-350. 2000. (Book Chapter)

 

286. Sherrod, L.A., Peterson, G.A., Westfall, D.G., and Ahuja, L.R. Carbon Sequestration rates after 12 years under no-till dryland cropping systems rotations. Proc. Great Plains Soil Fertility Conference, Denver, CO March 7- 8. Vol. 8:75-81. A. Schlegel (ed.). 2000. (Proceedings)

 

287. Wauchope, R.D., Nash, R.G., McDowell, L.L., Rojas, K.W., Ahuja, L.R., Willis, G.H., Moorman, T.B. and Ma, Q., Pesticide Processes. In L.R. Ahuja, Rojas, K.W., Hanson, J.D., Shaffer, M.J. and Ma, L., (eds.) Root Zone Water Quality Model. Water Resources Publication. Englewood, CO. pp.163-244. 2000. (Book Chapter)

 

288. Williams, R.D. and Ahuja, L.R. Using the Gregson One-parameter Model to estimate the soil water retention. Proc. Intern. Conf. Soil Dynamics. Univ. South Australia, Adelaide, South Australia. pp.26-30. 2000. (Proceedings)

 

289. Bakhsh, A., Hatfield, J.L., Kanwar, R.S., Ma, L. and Ahuja, L.R. Evaluation of Root Zone Quality Model for Simulation of Non-point Source Pollution from Agricultural Lands. Paper presented at the July 30- August 1, 2002 ASAE annual international meeting, Sacramento, CA. Paper No. 012187. ASAE, St. Joseph, MI. 2001. (Proceedings)

 

290. Baksh, A., Hatfield, J.L., Kanwar, R.S., Ma, L., and Ahuja, L.R. Simulating nitrate losses from Walnut Creek Watershed. A Paper presented at the 2001 ASAE Mid-Central Meeting. St. Joseph, MI., Paper No. MC01-405. March 31, 2001. (Technical Report)

 

291. Bakhsh, A., Kanwar, R.S., Jaynes, D.B., Colvin, T.S. and Ahuja, L.R. Preferential flow effects on NO3-N losses with tile flow. In Bosch, D. and King K. (eds.). Preferential Flow Water: Movement and Chemical Transport in the Environment. Proc. 2nd Intern. Symp., Jan. 3-5, 2001, Honolulu, HI. Am. Soc: Agricultural Eng., St. Joseph, MI. pp. 41-42. 2001. (Proceedings)

 

292. Green, T.R., Erskine, R.H., Martinez, A., Murphy, M.R., Ahuja, L.R., Salas, J.D. and Ramirez, J.A. Scaling relationships of crop yield and soil water content in an agricultural field: Measurement and topographic analyses. Proc. Intl. Congress on Modeling and Simulation, F. Ghissemi., et al (eds.) MODSIM 2001. Dec. 10-13. Canberra, Australia. pp. 359-369. 2001. (Proceedings)

293. Ma, L., Shaffer, M.J., and Ahuja, L.R., Application of RZWQM for soil nitrogen management. In Shaffer, M.J., Ma, L., and Hansen, S., (eds.). Modeling Carbon and Nitrogen Dynamics for Soil Management, CRC Press: Boca Raton, FL. pp 265-301. 2001. (Book Chapter)

 

294. Malone, R.W., Ma, L., Ahuja, L.R. and Rojas, K.W., Evaluation of the Root Zone Water Quality Model (RZWQM): A review, In: Parsons, J.E., Thomas, D.L., and Huffman, R.L. (eds.). Agricultural Non-Point Source Water Quality Models: Their Use and Application. Southern Cooperative Series Bulletin #398, ISBN: 1-58161-398-9. 2001. (Bulletin)

 

295. Ahuja, L.R., and Ma, L., Parameterization of agricultural system models: Current issues and techniques. In Ahuja, L.R., Ma, L. and Howell, T.A. (Eds.). Agricultural System Models in Field Research and Technology Transfer. CRC Press, Boca Raton, FL. pp 273-316. 2002. (Book Chapter)

 

296. Ahuja, L.R., Ma,L., Saseendran, S.A., and Andales, A.A. Agricultural system models in field research and technology transfer. Proc. International Agronomy Congress. Nov. 26-30. New Delhi, India. 2002. (Proceedings)

 

297. Ahuja, L.R., Ma, L., and Howell, T.A., Whole system integration and modeling: Essential to agricultural science and technology in the 21st century. In Ahuja, L.R., Ma, L., and Howell, T.A. (Eds.) Agricultural System Models in Field Research and Technology Transfer. CRC Press, Boca Raton, FL. pp 1-7, 2002. (Book Chapter)

 

298. Ahuja, L.R., Ma, L. and Howell, T.A. (eds.). Agricultural System Models in Field Research and Technology Transfer, Boca Raton, FL. CRC Press, 341pp. 2002. (Book)

 

299. Ahuja, L.R., Green, T.R., Erskine, R.H., Ma, L., Ascough II, J.C., Dunn, G.H., Shaffer, M.J., and Martinez, A., Topographic analysis, scaling and models to evaluate spatial/temporal variability of landscape processes and management. In Ahuja, L.R., Ma, L., and Howell, T.A. (eds.). Agricultural System Models in Field Research and Technology Transfer, CRC Publishers: Boca Raton, FL. pp 265-272. 2002. (Book Chapter)

 

300. Ahuja, L.R. and Ma, L. Computer models to guide soil water management for plants. In R. Lal, (ed.) Encyclopedia of Soil Science. Marcel Dekker, Inc. New York. pp 218-222. 2002. (Book Chapter)

 

301. Ascough II, J.C., Rector, H.D., Hoag, D.L., McMaster, G.S., Vandenberg, B.C., Shaffer, M.J., and Ahuja, L.R. Multicriteria spatial decision support systems: Review, case studies, and future research directions. Proc. International Environmental Modelling and Software Society (IEMSS) 2002 Conference. June 24-27. Univ. Lugano, Switzerland. 3:175-180. 2002. (Proceedings)

302. David, O., Markstrom, S.L., Rojas, K.W., Ahuja, L.R., and Schneider, I.W., The Object Modeling System. In Ahuja, L.R., Ma, L., and Howell, T.A., (eds.) Agricultural System Models in Field Research and Technology Transfer. CRC Press, Boca Raton, FL. pp. 317-330. 2002. (Book Chapter)

 

303. Ma, L., Nielsen, D.C., Ahuja, L.R., Kiniry, J.R., Hanson, J.D., and Hoogenboom, G., An evaluation of RZWQM, CROPGRO, and CERESmaize for responses to water stress in the Central Great Plains of the U.S. In Ahuja, L.R., Ma, L., and Howell, T.A. (eds.). Agricultural System Models in Field Research and Technology Transfer. CRC Press, Boca Raton, FL. Pp 119-148. 2002. (Book Chapter)

 

304. McMaster, G.S., Ascough, J.C., Shaffer, M.J., Byrne, P.F., Scott, D.H., Nielsen, D.C., Andales, A.A., Dunn, G.H., Weltz, M.A., and Ahuja, L.R. Parameterization of GPFARM: An agricultural decision support system for integrating science, economics, resource use, and environmental impacts. pp. Proc. International Environmental Modeling and Software Society Conferences. Univ. Lugano, Switzerland. 72-77. 2002. (Proceedings)

 

305. Peterson, G.A., Westfall, D.G., Peairs, F.B., Sherrod, L., Poss, I., Gaugloff, W., Larson, K., Thompson, D.L., Ahuja, L.R., Koch, M.D. and Walku, C.B., Sustainable dryland agroecosystem management. Colorado State Univ. TB01-02. 91pp. 2002. (Tech. Bulletin)

 

306. Nachabe, M.H., Ahuja, L.R., and Rokicki, R., Full capacity of water in soils, concepts, measurement and approximations. In Stewart, B.A. and Howell, T.A. (Eds.). Encyclopedia Water Science. Marcel-Dekker. pp.915- 918. 2003. (Book Chapter)

 

307. Saseendran, S.A., Ahuja, L. R., and Ma, L., Book review on crop-soil simulation models: applications in developing countries. J. Envrion. Qual. 32:2445-2446.2003. (Book Review)

 

308. Williams, R.D., and Ahuja, L.R., Scaling and evaluating the soil water characteristic using a one-parameter model. In Radcliffe, D.E., and Selim, H.M., (eds.) Scaling Methods in Soil Physics. CRC Press, Boca Raton, FL. pp. 35-40. 2003. (Book Chapter)

 

309. Ascough II, J.C., Green, T.R., Cipra, J.E., Vandenberg, B.C., Flynn, R.L., Norman, J.B., Ahuja, L.R., and Ma, L. 2003. AgSimGIS: Integrated GIS and Agricultural System Modeling. Proc. 2003 ESRI International User Conference, San Diego, California. July 7-11. (Conference Proceedings)

[http://gis.esri.com/library/userconf/proc03/p0309.pdf]

 

310. Ahuja, L.R., Ma, L., Andales, A.A. and Saseendran, S.A., Agricultural

system models in field research and technology transfer. Full chapter in Punjab Singh, I.P., S.Ahlawat, and R. C. Gautam (eds.). Proc. Second International  Agronomy Congress. Indian Soc. Agronomy. July, 2004. pp 226-233. 2004. (Book Chapter)

 

311. Ascough II, J.C., Green, T. R., Cipra, J. E., Ahuja, L. R., and Ma, L. Spacetime modeling of agricultural landscape variability using AgSimGIS.p. 10-21. In Ramirez, J.A. (ed.). Proc. Hydrology Days. March 10-21. Colorado State University, Fort Collins, Colorado. pp 10-21. 2004. (Proceedings)

 

312. Ma, L., and Ahuja, L.R., Book Review on “Mathematical Modeling for System Analysis in Agricultural Research”. Agricultural Systems. 81:273- 274. 2004. (Book Review)

 

313. Sherrod, L.A., Peterson, G.A., Westfall, D.G., and Ahuja, L.R. Carbon budget in dryland agroecosystems after 12 years in no-till as affected by climate, gradient, slope position, and cropping intensity. Proc. Great Plains Fertility Conference Proceedings. Denver, CO. pp. 234-239. 2004. (Proceedings)

 

314. Westfall, D.G., Peterson, G.A., Peairs, F.B., Sherrod, L.A., Poss, D.J., Shaver, T., Larson, K., Thompson, D.L., Ahuja, L.R., Koch, M.D., and Walker, C.B. Sustainable dryland agroecosystem management. Experiment Station Technical Bulletin TB01-05 Nov. 2004. (Technical Report)

 

315. Green, T.R., Ascough II, J.C., Ahuja, L.R., Ma, L., and Erskine, R.H. Model parameterization at different scales: How do we estimate and incorporate spatial information? Proc. Intl. Workshop on Applications, Enhancements and Collaborations of ARS RZWQM and GPFARM Models, April 20-22, Fort Collins, Colorado. pp. 60-61. 2004. (Proceedings).

 

316. Timlin, D., Williams, R.D., Ahuja, L.R. and Heathman, G., Simple parametric methods to estimate soil water retention and hydraulic conductivity. In Y. Pachepsky, and Rawls, W. (eds.). Development of Pedotransfer Functions in Soil Hydrology, Elsevier Publishers. pp. 71-94. 2005. (Book Chapter)

 

317. Ascough II, J. C., Green, T. R., Ma, L. and Ahuja, L. R. Key criteria and selection of sensitivity analysis methods applied to natural resource models. In: Zerger, A. and Argent, R. M. (Eds.). MODSIM 2005 International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2005, pp. 2463-2469. ISBN: 0-9758400-2-9. 2005. (Proceedings)

 

318. Anapalli, S.A., Nielsen, D.C., Ma, L., Ahuja, L.R., Vigil, M.F., Benjamin, J.G., Halvorson, A.D. Effectiveness of RZWQM for simulating alternative Great Plains cropping systems. Proceedings from the 35th Biological Systems Simulation Conference. April 19-21, 2005. Phoenix, AZ. pp. 37-38. 2005. (Proceedings).

 

319. Ascough II, J.C., Green, T.R., Ahuja, L.R., Ma, L., Vandenberg, B.C. 2005.  Spatial water quality modeling framework development using ArcGIS9. Proceedings 05-2082. ASAE Annual International Meeting, Tampa, FL. July 17-20, 2005. (Proceedings).

 

320. Heilman, P., Malone, R. W., Ma, L., Hatfield, J. L., Ahuja, L. R., Ayen, J., Boyle, K., and R. Kanwar. Decision Support for Nitrogen Management in Tile-Drained Agriculture. IEMSS. July 9-12 in Burlington, VT. 2006. (Proceedings).

 

321. Heilman, P., Malone, R. W., Ma, L., Hatfield, J. L., Ahuja, L. R., Ayen, J., Boyle, K., and Kanwar R. (2006). Decision support for nitrogen management in tile-drained agriculture. In: Voinov, A., Jakeman, A.J., Rizzoli, A.E. (eds). Proceedings of the iEMSs Third Biennial Meeting: "Summit on Environmental Modelling and Software". International Environmental Modelling and Software Society, Burlington, USA, July 2006. http://www.iemss.org/iemss2006/papers/s2/139_Heilman_1.pdf (Proceedings).

 

322. Ahuja, L. R. Ma, L., Kozak, J. A., Flerchinger, G. N., Anapalli, S. S., and Aiken, R. M. Modeling effects of till/no-till surface crop residues on soil water, temperature, and energy balance. ISTRO (International Conference on Soil Tillage Research), Kiel, Germany, Aug. 28-Sept. 3, 2006. (Proceedings).

 

323. Ma, L., Sherrod, L.A., Peterson, G.A., Hansen, N.C., and Ahuja. L.R. Soil Organic Carbon Pool Changes Under Long-term No-till and Cropping Intensity Regimes across an Evapotranspiration Gradient in Eastern Colorado, USA. ISTRO (International Conference on Soil Tillage Research), Kiel, Germany, Aug. 28-Sept. 3, 2006. (Proceedings).

 

324. Ahuja, L.R., Ma, L., Saseendran, A., and Malone. R. Application of agricultural system models in assessing and managing contamination of soilwater-atmosphere continuum in agriculture. AgroEnviron 2006: Fifth International Symposium on Agricultural Environment, Ghent, Belgium. Sept. 4-7, 2006. (Proceedings).

 

325. Del Grosso, S.J., Sherrod, L.A., Mosier, A., Peterson, G.A., Ahuja, L.R. and Hansen, N. Impacts of cropping intensity on soil C and net greenhouse gas fluxes for dryland cropping Northeastern Colorado. Proceedings Great Plains Soil Fertility Conference, Denver, CO, March 2008. (Proceedings).

 

326. Saseendran, S.A., Ahuja, L. R., Ma, L., Timlin, D., Stöckle, C. O., Boote, K. J., and Hoogenboom, G. Current water deficit stress simulations in selected agricultural system simulation models. Recent advances in understanding and modeling of water stress effects on plant growth processes. In Ahuja, L.R., Vangimalla, R., Saseendran, S.A., and Yu, Q (Eds.). Response of Crops to Limited Water: Understanding and Modeling Water Stress Effects on Plant Growth Processes. ASA-SSSA-CSSA series on Advances in Modeling Ag Systems. Madison, WI. pp 1-38. 2009. (Book Chapter).

 

327. Ma, L., Ahuja, L. R., and Bruuselma, T. Current Status and Future Needs in plant N Uptake Modeling: A preface. In Ma, L., Ahuja, L. R., and Bruuselma, T. (eds.). 2008. Quantifying and Understanding Plant Nitrogen Uptake for Systems Modeling. pp 1-11. 2008. CRC press. (Book Chapter).

 

328. Ma, L., Ahuja, L. R., and Bruuselma, T. (eds.). 2008. Quantifying and Understanding Plant Nitrogen Uptake for Systems Modeling. CRC Press. 313 pp. (Book).

 

329. Ascough II, J C, Ahuja, L R, McMaster, G.S., Ma, L., and Andales, A. A. 2008. Agriculture Models. Encyclopedia of Ecology. In: Jørgensen, Sven Erik and Fath, Brian D. (Editor-in-Chief), Ecological Models. Vol. [1] of Encyclopedia of Ecology, 5 vols. pp. 85-95. Oxford: Elsevier. (Book Chapter)

 

330. Ahuja, L.R., Vangimalla, R., Saseendran, S.A., and Yu, Q (eds.). Response of Crops to Limited Water: Understanding and Modeling Water Stress 60 Effects on Plant Growth Processes. ASA-SSSA-CSSA series on Advances in Modeling Ag Systems. Madison, WI. 436pp. 2009. (Book).

 

331. Ahuja, L.R., Vangimalla, R., Saseendran, S.A., and Yu, Q. Synthesis of papers and actions and further research to improve response of crop system models to water stress. In Ahuja, L.R., Vangimalla, R., Saseendran, S.A., and Yu, Q (eds.). Response of Crops to Limited Water: Understanding and Modeling Water Stress Effects on Plant Growth Processes. ASA-SSSACSSA series on Advances in Modeling Ag Systems. Madison, WI. pp. 411- 21. 2009. (Book Chapter).

 

332. Ahuja. L.R., Saseendran, S.A., Ma, L., Nielsen, D.C., Trout, T.J., Andales, A.A., and Hansen, N.C. Use of a cropping system model for soil-specific optimization of limited water. International Conference on Precision Agriculture Abstracts and Proceedings from the International Conference on Precision Agriculture, Denver, CO, July 20-23, 2009. (Proceedings).

 

333. Ahuja, L.R., Ma, L., Saseendran, S.A., and Fang, Q. X. Models of agricultural systems to guide research and optimal management of soilwater-nutrient resources and enhance environmental quality under varying climatic conditions. In: MacLeod, et al. (eds.). Aspects of Applied Biology 93: Integrated Agricultural systems: Methodologies, Modeling, and Measuring. June 2-4, 2009, SAC, Edinburgh, UK. (Conference Proceedings). http://qs.aqvs.co.uk/aab/images/P&BF_Modelling.pdf

 

334. Green, T.R., Erskine, R.H., Murphy, M.R., Ma, L., Ascough II, J.C., McMaster, G.S., Dunn, G.H., and Ahuja, L.R. Space-time dynamics of soil water and process interactions in semi-arid terrain, Colorado, USA. International Congress on Modeling and Simulation Proceedings from 18th World IMACS Congress and MODSIM09 International Congress on Modeling and Simulation, Cairns, Australia, July 13-17, 2009. (Proceedings).

 

335. Lloyd, W., David, O., Ascough II, J.C., Rojas, K.W., Carlson, J.R., Leavesley, G.H., Krause, P., Green, T.R., and Ahuja, L.R. Environmental modeling framework invasiveness: analysis and implications. In: Swayne, D.A., Yang, W., Voinov, A.A., and Filativa, T. (eds.). Proc. Fifth Biennial Conference of the International Environmental Modeling and Software Society; Modeling for Environment’s Sake, Ottawa, Canada, July 5-8, 2010, pp. 1073-1080 (Proceedings).

 

336. David, O., Ascough, J.C., Leavesley, G., Ahuja, L.R. Rethinking modeling framework design: Object Modeling System 3.0. In: In: Swayne, D.A., Yang, W., Voinov, A.A., and Filativa, T. (eds.). Proc. Fifth Biennial Conference of the International Environmental Modeling and Software Society; Modeling for Environment’s Sake, Ottawa, Canada, July 5-8, 2010, pp. 1183-119. 2010. (Proceedings).

 

337. Sherrod, L.A., Ahuja, L.R., and Hansen, N.C. No-till cropping system effects on soil profile organic carbon (0-24 inch) and total nitrogen after 7 years of drought. Great Plains Fertility Conf. Proceedings. March 2-3, 2010. Denver, CO. pp. 156-162. (Proceedings/Symposium).

 

338. Sherrod, L.A., Ahuja, L.R., Hansen, N.C., Larson, K., Thompson, D., Harn, D., and Thompson, C. 2010. Water storage and precipitation impacts on wheat and sorghum yields over 22 years at Stonington (Bill Wright Farm). Technical Report TR10-02 January 2009; Plainsman Research Center 2009 Research Reports; Agricultural Experiment Station, Colorado State University, pp 101-105. (Technical Report)

 

339. Ma, L., Ahuja, L. R., Saseendran, S. A., Malone, R. W., Green, T. R., Nolan, B. T., Bartling, P. N. S., Flerchinger, G. N., Boote, K. J., and Hoogenboom, G. A. Protocol for parameterization and calibration of RZWQM2 in field research. In: Ahuja, L. R. and Ma, L. (eds.). Methods of Introducing System Models into Agricultural Research, ASA-SSSA-CSSA book series. pp. 1-64. 2011. Madison, WI (Book Chapter)

 

340. Ahuja, L. R., and Ma, L. (eds.). Methods of Introducing System Models into Agricultural Research, ASA-SSSA-CSSA series on Advances in Modeling Ag Systems. Madison, WI. 450 pp. 2011. (Book).

 

341. Ahuja, L. R., and Ma, L. A synthesis of current parameterization approaches and needs for future improvements. In: Ahuja, L. R. and Ma, L. (eds.). Methods of Introducing System Models into Agricultural Research, ASA-SSSA_CSSA series on Advances in Modeling Ag Systems. Madison, WI. pp. 427-440. 2011. (Book Chapter).

 

342. Reyes-Fox, M.A., Del Grosso, S.J., Sherrod, L.A., Peterson, G.A., Ahuja, L.R., and Hansen, N. Can Daycent represent impacts of slope and cropping intensity on soil C and yield for dryland systems in Eastern Colorado? Proc. Great Plains Soil Fertility Conference, Denver, CO. March, 2012. (Proceedings).

 

343. Saseendran, S. A., Ahuja, L. R., and Ma, L. Development of crop production functions for crops in Colorado using RZWQM2 model. Documentation submitted to Regnesis Management Group LLC., Denver, CO. 49pp. 2012. (Technical Report)

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