Research Project: Precipitation and Irrigation Management to Optimize Profits from Crop Production

Location: Soil and Water Management Research

2018 Annual Report

Objectives
Objective 1: Develop improved methods and sensor systems for determining crop water use and stress, and integrate these into systems for water management. Sub-objective 1.1: Improve understanding of soil water status and sensing. Sub-objective 1.2: Improve determinations of evapotranspiration (ET). Sub-objective 1.3: Improve water management decisions at multiple scales by incorporating a better understanding of ET into hydrological models. Objective 2: Develop irrigation and sensor technologies, and best management practices for different irrigation application systems and technologies. Sub-objective 2.1: Compare crop water use efficiency (WUE) and partitioning of water use between evaporation (E) and transpiration (T) between subsurface drip (SDI) and sprinkler irrigation systems. Sub-objective 2.2: Develop sensors and algorithms to improve decision support for an irrigation scheduling supervisory control and data acquisition (ISSCADA) system to spatially optimize crop yields and WUE. Sub-objective 2.3: Develop irrigation application strategies that vary water application temporally for improved cotton lint yields. Objective 3: Develop and determine best management practices to maximize WUE, and long-term profitability using multi-year rotations of different crops and cropping practices, including both dryland and intermittent irrigation practices. Sub-objective 3.1: Determine if long-term weather predictions can be used to optimize irrigation strategies for increased WUE and yield. Sub-objective 3.2. Determine the effects of different conservation tillage practices on precipitation capture and harvest in relation to crop rotation phase. Sub-objective 3.3: Evaluate crop yield response to varying levels of deficit irrigation and water stress under differing management (Genetics x Environment x Management, G x E x M).

Approach
The Ogallala Aquifer region of the U.S. is one of the primary crop production areas in the country, in part because it overlays one of the country’s largest fresh water aquifers. But water availability from the aquifer has decreased significantly since the beginning of wide-spread irrigation in the 1950s, with the greatest impact on the Southern and Central High Plains of western Kansas and Texas. Responding to this will require both more efficient water use by irrigation and increased productivity with lower risk from dryland farming. Cropping practices such as rotation with fallow period for soil water recharge and irrigation practices that avoid evaporation address many of the unique needs of the Central and Southern Great Plains. However the need remains for more efficient water use in these semi-arid regions. Therefore this project will research three areas. First, a better understanding of soil water movement and evaporation, and evapotranspiration. Second, sensors that monitor soil water and crop water stress will be developed to effectively and efficiently use the remaining groundwater for irrigated crop production. Finally, the project will develop best management practices for using water more efficiently under dryland and marginal irrigation regimes. These results will enable the region to remain a competitive area for crop production, sustain farm based communities, and maintain the strength of American agriculture in world markets. Research will be conducted in laboratory and field situations from scales of small plots to regions where crop related data is extracted from remotely sensed images. New plant and soil water stresses will be developed in the laboratory, and once refined, field tested. Data will be integrated into prescriptions for dynamic site specific irrigation scheduling that account for well capacities. These will be tested under field conditions. Understanding of methods to measure evapotranspiration, like eddy covariance, COSMOS, etc., will be enhanced by comparing values from large weighing lysimeters and accurate water balance derived from neutron probe measurements for the soil profile. Measurements from microlysimeters and soil heat flux plates will be used in the field to provide better separation of measures of evaporation and transpiration components of evapotranspiration. A better understanding of evapotranspiration will be used to guide the development of best management practices for crop production and those practices will be tested under field conditions. Data will be used to refine existing hydrologic models, including AcrSWAT, Aquacrop, etc. Data bases of crop water use will be developed and made available to other scientists. This research project also leads the Ogallala Aquifer Program, a research-education consortium addressing solutions arising from decreasing water availability from the Ogallala Aquifer in western Kansa and the Texas High Plains. The consortium includes the ARS NP211 projects at Bushland and Lubbock, Texas, Kansas State University, Texas A&M AgriLife Research and Extension Service, Texas Tech University and West Texas A&M University.

Progress Report
Research in the project continues to progress as per the approved project plan. All eighteen milestones proposed in the project's research plan were either substantially or fully met in FY2018. The weather during FY2018 has been unusually dry with little precipitation occurring during the winter and spring seasons. Rain has been scarce during the first half of the summer of 2018. Dry conditions hampered data collection from dryland research experiments. Runoff from dryland watersheds that had been continuously monitored from 1958 to 2015 when excessive rain damaged the existing terrace structures isolating the watersheds. These terraces were renovated in FY2017 and 2018 (Milestone 16). However, no runoff data has been collected in FY2018 because of droughty conditions. The four large weighing lysimeters continued to be one of the most utilized resource of the research unit. Alfalfa had been proposed in the approved project plan as the subject of investigation for the large weighing lysimeters starting in FY2018. However, alfalfa was replaced with corn for the experiments on the large weighing lysimeters. Corn allows for better estimates of soil evaporation, especially early in the growing season when the crop is smaller, and its management is of more interest to stakeholders. In addition, corn has been a subject of investigation in previously years; additional data were needed to confirm results. Instrumentation and data collection related to five milestones involved the large weighing lysimeters facility in FY2018. Irrigation scheduling by Time Domain Reflectometry (TDR) soil moisture for maize was one avenue of investigation for the large weighing lysimeter fields in FY2018 (Milestone 1). Data collection regarding water sensing by the COSMOS system continued in FY2018 and data from COSMOS were compared to soil moisture measurements by the large weighing lysimeters, and neutron and TDR probes (Milestone 2). Large weighing lysimeters are expensive to install and maintain. Other accurate means for measuring crop ET are needed. ET measurements by laser scintillometers and eddy covariance systems are being compared to data from the large weighing lysimeters (Milestone 4). These methods still lack the accuracy that large weighing lysimeters provide. A relative new series of investigations to use imagery from unmanned aerial systems (UAV) to estimate ET was started in FY2018 (Milestone 5). Data from the large weighing lysimeters are invaluable for validating and calibrating other measurements of ET including remotely sensed images. Irrigation scheduling based on crop canopy temperatures by stationary IRT and soil moisture values by either neutron probe or TDR senses continued for a second year using the large weighing lysimeters fields (Milestone 12). Because two of the four large weighing lysimeter fields were irrigated by subsurface drip and the other two were by sprinkler, thus, the data collected from these fields in FY2018 compared the effects of irrigation method on soil evaporation and other components of ET (Milestone 8). Research into advanced irrigation scheduling and automation continued using 3- and 6-span center pivot irrigation systems. Under the 3-span irrigation system, ET measurements from two-source energy balance model combined with data on soil moisture values from either neutron or TDR probes were used to guide irrigation applications and compared to irrigations scheduled by manual calculations of changes in soil moisture from neutron probe measurements (Milestone 10). Under the 6-span center pivot irrigation system growing sorghum, the use of computer visual device and Irrigation Scheduling Supervisory Control and Data Acquisition (ISSCADA) system using feedback from plant and soil measurements were tested and compared to manual scheduling of irrigation application using changes in soil moisture by neutron probe readings (Milestones 11 and 12). These instruments were also used to refine the software and hardware to acquire thermal and IR images of irrigated crop canopies under field conditions (Milestone 18). Under these center pivots, irrigation scheduling using either plant or plant and soil data were being compared to scheduling using soil moisture measurements from neutron probes (Milestone 9). The unit's unique Soil-Plant-Environment Research facility was used for the third year of experiment examining if water stress could be used to initiate cutout of cotton flowering to encourage the fuller development of cotton bolls and improve lint quality (Milestone 14). This facility included smaller lysimeters of four soil types common to the Southern Great Plains and a rainout shelter for precise control of soil water content. Field experiments comparing the response of new drought tolerant maize to conventional hybrids to varying amount of irrigation water were conducted under a linear move irrigation system (Milestone 17). The data from field experiments, especially those related to ET from the large weighing lysimeters, are an exceptional resource in the development and refinement of hydrological models. Four of the milestones (3, 6, 7,15) in FY2018 were related to this area of research. The current irrigation routines within Soil Water assessment Tool (SWAT) simulate these activities poorly. Changes in program coding enabled researchers to simulate irrigation by the management allowance depletion method. This change in the programming was evaluated and found to more accurately reflect this method of irrigation scheduling than the previous routines. SWAT also uses a rudimentary crop growth model as part of its means to simulate ET portion of the hydrological cycle. It has been reported previously that the existing crop model in SWAT did not accurately simulate crop leaf area index over the course of a growing season, an important determinant of ET and crop yields. Researchers in this project have been examining other crop models that can be used an input to better simulate leaf area index. These studies were ongoing in FY2018. Weather data consistent with La Nina and El Nino weather cycles were used as input into SWAT to better understand on these long term weather trends may affect dryland crop production over the Texas High Plains. El Nino climate conditions were related to better wheat grain yields. Cooperative research with commercial partners continues under two different CRADAs and two MTAs, one of which is new in FY18. Project's scientists cooperated with numerous researchers in the United States and in eleven other countries. Research results in FY18 generated 27 accomplishments. Of these, fifteen had ARS scientists as principle investigators (PIs). These accomplishments related to irrigation management, dryland production practices and the refinement of hydrological models. The remaining 12 accomplishments had PIs from Kansas State University, Texas A&M AgriLife Research and Extension Service, Texas Tech University or West Texas A&M University. These accomplishments were conducted via the Ogallala Aquifer Program (OAP) and its four related non-assistance cooperative agreements (NACAs). Research in the OAP was directed towards one or more of five objectives: 1) Develop water management strategies and technologies that could reduce water withdrawals by 20% in 2020 as compared to 2012 maintaining farm profitability; 2) develop management strategies and technologies that increase the sustainability of dryland cropping systems; 3) improve the understanding of hydrological and climate factors that affect agriculture; 4) determine the impact of water policies; 5) develop best management for alternative crops. ARS scientists at Bushland in conjunction with the OAP sponsored events to celebrate 40 years of sprinkler research on the High Plains. These include: 1) Field days at Bushland, Texas, and Garden City, Kansas; and 2) special technical sessions at the annual meeting of the American Society of Agricultural and Biological Engineers, and Irrigation Association.

Accomplishments
1. Managed deficit irrigation can save 6 inches of irrigation per acre and boost yields. Development of sustainable and efficient irrigation strategies is a priority for agricultural producers faced with water shortages. A promising management strategy for reducing water use is managed deficit irrigation, in which the crop is not fully irrigated but greater irrigation is applied during grain set and early fill. However, experimental results are lacking for this irrigation strategy. Thus, ARS scientists from Bushland, Texas collaborated with Texas A&M AgriLife Research and Extension Service to study managed deficit irrigation with grain sorghum. Managed deficit irrigation averaged 25 bushel per acre more than deficit irrigated sorghum using only 1.5 inches of additional irrigation as compared to nearly 8 inches with fully irrigated sorghum. If irrigation water is limiting, Managed Deficit Irrigation (MDI) has significant advantages over deficit irrigation.

2. Corn under mobile drip irrigation requires less irrigation water for similar yields. Since water availability for irrigation from the Ogallala Aquifer is declining; farmers in the Texas High Plains region are interested in mobile drip irrigation as a means to reduce groundwater withdrawals while maintaining crop yields. However, there is limited information on the performance of the mobile drip irrigation MDI system and its benefits. ARS scientists at Bushland, Texas with support from the High Plains Water District conducted a two-year study to compare corn production irrigated with mobile drip irrigation to low elevation sprinklers and low energy precision application (LEPA) drag socks. Results indicated that in a year with above average summer rainfall, there was little difference in yields among the three application methods. Corn under the mobile drip irrigation required about one inch less to produce optimum yields. However, during a year with less than average summer rainfall, corn irrigated with the mobile drip irrigation system required at least three inches less water to produce similar grain yields. These results could help sustain irrigated agriculture on farms that have limited well capacity.

3. Hand held device can estimate virus infection in irrigated wheat. Approximately three million acres of winter wheat are grown in the Texas High Plains region, with one-third being irrigated. A critical issue for farmers is that wheat is susceptible to Wheat Streak Mosaic Virus (WSMV), which is transmitted by the wheat curl mite. If infected early in the season, the wheat will produce little to no yield. ARS scientists /at Bushland, Texas, along with researchers at Texas A&M AgriLife, demonstrated that a hand held meter which detects different colors of light (green in this case) can be used to identify WSMV infection in a field in early spring. Wheat crops with high levels of infection should not be irrigated because the crop will not use the additional water. This is an important finding for producers as early detection with this sensor can limit water waste.

4. Canopy temperatures and weather data successfully schedule irrigation applications. Corn is an important crop for cattle feed on the Texas High Plains. However, water for agriculture in this area is limited. Therefore, ARS scientists in Bushland, Texas used canopy temperature and weather data (feedback) to determine whether areas within a corn field were water-stressed. If the crop was stressed, water was applied. These results were compared to corn that was scheduled manually using a very accurate soil water probe. In the feedback plots, grain and biomass yields, the amount of water that the crop used and yield per amount of water were similar to the manually scheduled plots. Farmers could use this system that will be available soon from Texas A&M AgriLife as a download to help improve irrigation management of corn by maintaining yields but preventing under-and over-watering.

5. Narrow row cotton does not promote dryland cotton lint yields. Dryland farming may replace irrigated acres as water from the Ogallala Aquifer becomes scarce. Cotton is a good dryland crop if new farm practices can offset the yield limiting growing season on the southern High Plains. Scientists from Bushland, Texas and Texas A&M AgriLife Research and Extension Service tested row and plant spacings on cotton fiber quality and yield using field plots. Cotton grown in narrow, 25 to 50 cm row widths and 7.5 to 10 cm frequency were shorter and had fewer bolls per plant than with common 76 cm rows. These results show farmers, extension agents and crop consultants that dryland cotton planted with narrow row and plant spacing did not yield higher.

6. Tillage is required to sustain grazing of dryland wheat and sorghum. Water availability for irrigation from the Ogallala Aquifer is declining on the southern High Plains, and to maintain farm income with reduced water withdrawals, dryland row crop agriculture will need to intensify. The current three-year dryland wheat-sorghum-fallow rotation has stabilized crop production except under extended drought. Inclusion of grazing cattle at various stages of the rotation can increase income potential; however, the sustainable management protocols that preserved the infiltration of rain have not been adequately identified. Therefore, grazing and no-till (NT) or stubble-mulch (SM) tillage effects on rain infiltration and soil loss and stability were compared by ARS scientists from Bushland, Texas. Infiltration did not differ significantly with grazing. Soil loss from sorghum fallow increased with grazing and SM tillage. With good residue, SM tillage after grazed wheat increased infiltration greater than 100 % over NT. Occasional SM tillage is recommended to wheat farmers that combine grazing and NT. These results apply to grazing wheat throughout the southern Great Plains.

7. Critique of soil water sensors published. New and improved soil water sensor technologies are being promoted for the assessment of crop water use and to schedule irrigation. However, the accuracy of some of the sensors is questionable thereby requiring evaluation under field settings where they will be used. ARS scientists from Bushland and Lubbock, Texas critiqued several available soil water sensors and showed that some results can be misleading. This critique provides helpful guidance for better research practices in the future that will provide farmers, extension agents and crop consultants with better information for guiding the use of soil water sensors to schedule irrigation.

8. Low wheat yields are unlikely with El Nino on the Texas High Plains. Decades of pumping with minimal recharge has resulted in declining levels of the Ogallala Aquifer in the Texas High Plains. A gradual transition to more dryland management systems including winter wheat cropping rotations is expected. Precipitation forecasting approaches may help producers manage crops accordingly. However, the use of these forecasting approaches have not been fully investigated. It is now known that temperatures in the Pacific Ocean affect the climate in North America, especially the southwestern region of the U.S. These Pacific Ocean temperature trends were used to separate years into relatively wet (El Nino) and dry (La Nina) phases using historical measured precipitation data from the ARS laboratory at Bushland, Texas. Analyses of simulated wheat yield values revealed a reduced likelihood of lower grain yields for El Nino phases. Therefore, predictions of El Nino or La Nina may be a useful tool to determine the level of inputs for dryland crop production on the Texas High Plains.

9. Kansas Water Budget adequately predicts sorghum and wheat yields for the Southern High Plains. As water available for irrigation from the Ogallala Aquifer decreases, dryland farming will become more common place on the Southern High Plains. Farmers will need information on dryland yield potential based on weather forecasts to determine the optimum levels of inputs. However, currently the ability to predict wheat and sorghum yields is rather limited. Therefore, ARS scientists from Bushland, Texas worked with researchers in the Ogallala Aquifer Program at Kansas State University to better forecast dryland sorghum and wheat grain yields from weather variables and water use. Crop production functions relating water use and grain yield were developed based on the Kansas Water Budget (KSWB). The KSWB model was found to be an useful decision support tool for relating water supply to grain yield. In the future farmers may be able to combine short term weather forecasts (30-90 days) with KSWB to determine yield potentials and the optimum levels of inputs including irrigation applications.

10. A commonly used crop model overestimates crop growth and water use. Water scarcity due to drought and groundwater depletion has led to an increased number of modeling studies aimed at evaluating crop response to limited irrigation. The Decision Support System for Agrotechnology Transfer (DSSAT) is a widely used crop growth model. However, the ability of this model to simulate crop response and water balance under limited irrigation has not been well studied. Therefore, scientists from ARS, Bushland, Texas and Texas A&M AgriLife compared simulated and measured plant growth values for corn grown in the Texas Panhandle under full and limited irrigation. Results showed that this model overestimated corn growth, yield, and crop water use under limited irrigation. These results are of interest to agronomist, plant physiologists and crop modelers because they demonstrate the weakness of the current model to simulate corn growth under less than ideal growing conditions.

11. Design for sub-surface drip irrigation for a large lysimeter. Conservation of scarce water supplies have encouraged farmers on the Southern High Plains to adopt new irrigation technologies with the hope that groundwater withdrawals can be reduced while maintaining or increasing crop yields. The large weighing lysimeters at the ARS research location in Bushland, Texas provide important information on crop water use that can be used for scheduling irrigation applications. These results have been limited to those farms using sprinklers such as center pivots as the application method. However, the occurrence of subsurface drip irrigation (SDI) has increased substantially in the past 10 to 15 years in part because of cost share on installation from NRCS-USDA. Therefore, ARS scientists from ARS at Bushland, Texas devised a method to install and use SDI on two of the four large weighing lysimeters located in Bushland, Texas. These installations will allow for precise comparison of crop water use between crops grown under sprinklers and SDI in the near future.

12. Drought is more likely the further west on the Texas High Plains. Drought conditions are common in areas such as the Texas High Plains and can cause large agricultural losses. To minimize drought impacts, it is beneficial to understand how likely certain levels of drought can be. However, such data are not readily available for the Texas High Plains. Therefore, scientists from ARS in Bushland, Texas and El Reno, Oklahoma and researchers from Texas A&M AgriLife Research and Extension Service calculated the likelihood of drought conditions throughout the Texas High Plains, based on a standard index, and found that drought conditions are very likely throughout the summer months. Drought conditions decreased from West to East, possible in response to rainfall increasing from West to East. These data can provide useful information for managing water in this region.

13. The auto-irrigation part of a commonly used hydrologic model cannot simulate irrigation practices. Water scarcity due to drought and groundwater depletion has led to an increased emphasis on irrigation strategies for extending limited water resources. Models are commonly used to assess the impacts of such strategies. The Soil and Water Assessment Tool (SWAT), a widely used hydrologic model, is increasingly being used to evaluate the impacts of irrigation strategies at both field and watershed scales. However, concerns about the ability of the auto-irrigate function in SWAT to simulate actual irrigation practices have tempered results. Scientists from Bushland, Texas and Texas A&M AgriLife compared simulated irrigation, crop water use, plant growth, and yield to measured values for crops grown in the Texas High Plains. Results showed that the auto-irrigate function was unable to represent irrigation practices of the region, prompting the need for revision of the auto-irrigation algorithm in SWAT. Although users of SWAT have expressed dissatisfaction with the auto-irrigation regime, this is the first report establishing the inability of the routine to simulate current irrigation practices.

14. Farm model Agricultural Policy Environmental eXtender (APEX) underestimates crop water use. Freshwater resources are becoming scarce and subject to nutrient pollution from agricultural use. Modeling tools such as the APEX model are used to evaluate the effects of management practices on water quality. Meaningful evaluation is dependent on accurate simulation of water balance components. However, limited work has been done to assess the model's ability to estimate evapotranspiration (ET). In this study, researchers from Bushland, Texas compared simulated ET from five methods to measured ET values from Bushland, Texas. Results indicated that APEX generally underestimated ET for crops grown in the semi-arid Texas High Plains. These results are of interest to SWAT users and those that use model results for water planning and policy decisions.

15. Cover crops in western Kansas may decrease wheat yields by decreasing soil water. Recently there has been a great interest in the use of cover crops to promote soil health and reduce erosion. However, there is a debate whether planting cover crops will be beneficial in areas where crop production is limited by rainfall, because the cover crop may deplete soil water for crops that produce farm income. Therefore, scientists from Kansas State University in the ARS led Ogallala Aquifer Program at Bushland, Texas studied replacing fallow in no-till winter wheat–fallow rotation with cover, forage, or grain crops. Plant available water at wheat planting was reduced the most when the fallow period was replaced with a summer grain crop. For every inch of saved soil water at planting, wheat yields increased by 2.5 bushels per acre (about $12.5 per acre). Wheat yields were depressed least when the summer fallow was replaced with a short season annual forage.

16. No-till promotes higher yields of dryland wheat and sorghum in western Kansas. As available water for irrigation from the Ogallala Aquifer decreases, more land owners are likely to farm more dryland (rain-fed) acres. Tillage is an important cropping practice that affects yield, profitability, and environmental quality, especially with dryland farming. However, the responses of crops to different tillage practices are site specific and vary with crop rotations. Therefore, scientists from Kansas State University in the ARS led Ogallala Aquifer Program at Bushland, Texas conducted a long term investigation (26 years) of the effects of different tillage practices on a dryland wheat-grain sorghum-fallow rotation in western Kansas. On average, there was a 31% wheat yield advantage for no till over stubble much tillage, and 120% sorghum yield advantage for no till over stubble mulch tillage. Farmers interested in greater crop yields should consider no-till over stubble mulch tillage.

17. Water requirement for optimum grain yields less with modern corn hybrids. Corn is the major irrigated crop on the Texas High Plains (THP) using over 50% of the total irrigation water. Currently, high level corn production is challenged because of the declining water in the Ogallala Aquifer and water policies of regional groundwater conservation districts. However, management practices for sustainable high corn yields with less irrigation water needs are to be refined. Scientists from Texas A&M University in the ARS led Ogallala Aquifer Program at Bushland, Texas evaluated corn management practices on the THP with reduced or limited levels of irrigation over the last forty years. With recent advances in corn breeding and genetics, irrigation requirements can be reduced by up to 25% in some years with grain yields comparable to full irrigation. Among management practices, irrigation remains the single-most important factor affecting corn yields, with some effects from planting date, and seeding rate.

18. Drought tolerance in dryland wheat related to its ability to use soil water from deeper depths. Drought is the most important factor limiting wheat yields on the U.S. southern High Plains (SHP). Adoption of suitable cultivars and crop management practices are crucial to reducing yield loss from drought, however, the parameters associated with tolerance to drought are not fully known. Therefore, scientists from Bushland, Texas, Texas A&M University and North Dakota State University conducted a 5-yr study to investigate soil water extraction by four wheat cultivars. There were large variations in grain yields (474 to 3,685 kg per ha) in dryland wheat across years and cultivars. Yield was largely determined by plant available soil water at planting and seasonal precipitation. More recent cultivars (TAM 110, TAM 111, and TAM 112) were able to extract more water from deeper in the soil profile than the legacy wheat cultivar, TAM 105, especially during the dry years seasons. This study demonstrated that effective use of soil water from greater soil depths is important for wheat yields on the Southern High Plains.

19. Heavy early season irrigation is wasteful for cotton production on the Texas High Plains. Decreased groundwater under the Texas High Plains has increased the risks associated with irrigation. However, timing application of irrigation boosts crop yields significantly in most years. Therefore, scientists from Texas Tech University, and Texas A&M University in the ARS led Ogallala Aquifer Program at Bushland, Texas investigated 27 irrigation treatments combining time of application and amount of applied water using cotton as the crop. Heavy irrigation early in the growing season used more water, did not increase boll number, and was often detrimental to yield. Mid- and late-season irrigation improved yield and fiber quality. These results provide insight into optimizing cotton water use in a region with declining crop water availability, increased pumping restrictions, and a challenging climate.

20. ARS’Ogallala Aquifer Program is helping to train the next generation of agricultural engineers. Advances in farming across the U.S. and the High Plains will require the development of capable and skilled labor force. However, many students are "booked learned" and gain little practical experience in the design and production of farm equipment. Therefore, professors from West Texas A&M University and University of New Haven in the ARS led Ogallala Aquifer Program at Bushland, Texas had students in the mechanical and civil engineering programs work on a variety of engineering projects. This specific project designed, built and evaluated a solar distillation apparatus that can "clean up" wastewater from livestock production systems on farms. Students gain practical experience in engineering design and equipment production that should prepare them better for future agricultural related jobs.

21. Water policies need to take into account crop prices, input costs and discount rate. Agriculture plays a vital role in the sustainability of the economy of the High Plains Region of the United States. With the development and adoption of irrigation technology, this region was transformed into one of the most agriculturally productive regions in the world. The primary source of irrigation in this region is the Ogallala Aquifer. Currently, water from the aquifer is being used at a much faster rate than natural recharge can occur, resulting in a high rate of depletion. Not enough is known how this depletion of groundwater will effect regional economic sustainability. Scientists from West Texas A&M University and Kansas State University in the ARS led Ogallala Aquifer Program at Bushland, Texas evaluated the impact alternative prices and discount rates on groundwater policy recommendations. As indicated by results of this study, crop prices, input costs, and discount rates have an impact on the effectiveness of water policies that encourage fewer irrigated acres. These results are of interest to water policy makers when estimating changes in farm economy with changes in groundwater policy.

22. A coupled natural-human model can help guide water policy decisions. As water from the Ogallala Aquifer decreases, water policy makers need information on the impact of future water policies on socio-economic impacts. However, the tools for developing such information to guide water policy formulation is still under development. Scientists from Kansas State University, Pennsylvania State University, Auburn University and University of Minnesota in the ARS led Ogallala Aquifer Program at Bushland, Texas studied the impact of water policy on conserving the Ogallala Aquifer in Groundwater Management District 3 in southwestern Kansas using a model that simulates a coupled natural–human system. The findings corroborate previous studies showing that conservation often leads to an initial expansion in irrigation. This study supports the use of a-coupled-natural-human model to understand the effects of changes in groundwater policy.

23. Wastewater can be "cleaned up" by solar distillation. As water availability from the Ogallala Aquifer decreases, other sources of fresh water will need to be pursued to make up from lost supply. However, there is a lot of waste water of low quality on the Texas High Plains from electricity production, livestock processing, oil and gas mining, towns and cities, etc. Therefore, processes to produce usable water from waste streams need to be developed and tested. Scientists from West Texas A&M University and the University of New Haven in the ARS led Ogallala Aquifer Program at Bushland, Texas tested the ability of a solar distillation system to treat wastewater. Analyses demonstrated that such a process is feasible for reclaiming water on farms.

24. Contaminants in wastewater from beef feedlots can be removed. Other sources of high quality water will need to be identified and developed as available water from the Ogallala Aquifer decreases. Cattle feedlot runoff and waste water contains substantial concentrations of salts, nutrients, pathogens, and organic matter, which limits its reuse. However, processes that can separate these contaminants from the water need to be developed. Therefore, scientists from West Texas A&M University and Cleveland State University in the ARS led Ogallala Aquifer Program at Bushland, Texas studied the efficiency of treating feedlot wastewater with an electrocoagulation process. The results demonstrated that most contaminants could be removed. These findings are vital for the development of methods to generate "clean" water from feedlot wastewater.

25. Cotton with a gene that decreases sensitivity to a plant hormone are drought tolerant. As available water from the Ogallala Aquifer for irrigation decreases, farmers will need to reduce withdrawals from the aquifer. The use of varieties that use less irrigation water per unit of yield is one way that farmers can reduce withdrawals and maintain farm sales. However, basic knowledge of the physiological processes that contribute to efficient water use must be identified. In previous studies, cotton that was insensitive to the plant hormone abscisic acid (ABA) tended to be drought tolerant. However, the exact mechanism for this drought tolerance has not been identified. Therefore, scientists from Texas Tech University, Texas A&M University and University of California-Davis in the ARS led Ogallala Aquifer Program at Bushland, Texas investigated transgenic cotton lines with genes that impart insensitivity to ABA. Results substantiate the potential for engineering drought tolerance in agricultural crops such as cotton by over-expression of these genes. This information is of value to other crop breeders and plant physiologists working towards enhanced drought tolerance in major crops for the southern High Plains.

26. A gene from fruit flies may aid in the development of drought tolerant crops. As available water from the Ogallala Aquifer for irrigation decreases, farmers will seek crop varieties that are more water efficient. Conventional plant breeding methods have increased the yield potential of many commonly grown crops including cotton, wheat and corn. Traditional breeding methods tend to increase crop yields in a progressive, incremental manner. However, transgenetic technologies may increase crop water use by a rapid leap forward. A gene from fruit flies may increase the expression of introduced genes in transgenetic plants. Therefore, scientists from Texas Tech University, Chengdu Institute of Biological Products Co. (China), Henan Academy of Agricultural Sciences (China), Recep Tayyip Erdogan University (Turkey) and Sichuan University (China) in the ARS led Ogallala Aquifer Program at Bushland, Texas examined the effects of this fruit fly gene on the expression of two plant genes introduced into a model plant. The results showed that the fruit fly gene does promote the expression of two plant genes introduced into plants without the gene. These results are of interest to plant molecular biologists and crop breeders trying to increase the expression of desired traits.

27. A biochemical factor that promotes drought gene expression identified in cotton. Drought is a key limiting factor for cotton production, with more than half of the global cotton supply being grown in regions in which water supply is limited. The use of drought resistant cotton varieties is one way farmers can continue to grow cotton in such areas. However, the underlying mechanism of the response of cotton to drought stress remains elusive. Scientists from Texas A&M University and China Agricultural University along with ARS researchers at Bushland, Texas identified a protein factor that interacts with genes to regulate the drought stress response in cotton. This is an important step forward in understanding the drought response in crops and may aid in the development of improved varieties in the future.

Review Publications
O'Shaughnessy, S.A., Colaizzi, P.D. 2017. Performance of precision mobile drip irrigation in the Texas High Plains region. Agronomy. 7(4):68. https://doi.org/10.3390/agronomy7040068.
Baumhardt, R.L., Schwartz, R.C., Marek, G.W., Bell, J.M. 2018. Planting geometry and growing season effects on the growth and yield of dryland cotton. Agricultural Sciences. 9(1):99-116. https://doi.org/10.4236/as.2018.91008.
Schwartz, R.C., Evett, S.R., Lascano, R.J. 2018. Comments on "J. Singh et al., Performance assessment of factory and field calibrations for electromagnetic sensors in a loam soil [Agric. Water Manage. 196: 87-98]. Agricultural Water Management. 203:236-239.
O'Shaughnessy, S.A., Andrade, M.A., Evett, S.R. 2017. Using an integrated crop water stress index for irrigation scheduling of two corn hybrids in a semi-arid region. Irrigation Science. 35(5):451-467.
Saleh, A., Niraula, R., Marek, G.W., Gowda, P.H., Brauer, D.K., Howell, T.A. 2018. Lysimetric evaluation of the APEX Model to simulate daily ET for irrigated crops in the Texas High Plains. Transactions of the ASABE. 61(1):65-74. https://doi.org/10.13031/trans.11938.
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