Location: Delta Water Management Research
2019 Annual Report
Objectives
Objective 1: Measure, model, and/or estimate the impact of current and innovative farming practices on water quantity and quality while sustaining crop yields and reducing environmental impacts in irrigated agroecosystems.
Sub-objective 1a: Quantify changes in irrigation water use, water quality, and crop water productivity as a result of implementing innovative rice production practices.
Sub-objective 1b: Quantify changes in irrigation water use, water quality, and crop water productivity as a result of implementing innovative row-crop production practices.
Objective 2: Develop and/or enhance agronomically sound irrigation and drainage management tools, practices, and technologies that protect and/or increase available water resources.
Sub-objective-2a: Evaluate alternative sources of irrigation water.
Sub-objective-2b: Evaluate practices and technologies for managed recharge of the MRVA aquifer.
Objective 3: Improve watershed management in irrigated agroecosystems of the Lower Mississippi River Basin.
Sub-objective 3a: Develop an improved understanding of nutrient and sediment transport, transformations and the hydrology in an irrigated landscape.
Approach
To preserve the quantity and quality of irrigation water supplies in the Lower
Mississippi River Basin, it is necessary to consider the range of crops, soils, and production systems; the types of irrigation and drainage systems employed; the level of runoff water recycling employed; and the different water sources available. This project will address ways to improve the sustainability of groundwater supplies by investigating alternative irrigation methods for the crops currently produced in the region. Production system evaluations will include on-farm research with active participation by crop producers and crop advisors. Data collected from on-farm evaluations will be used to inform, enhance and validate existing hydrology models. Findings from this research are expected to reduce agricultural reliance on groundwater and improve water resources management, inform decision makers of potential impacts of conservation practices, and arm producers with tools and technologies that conserve water resources while maintaining crop yield.
Progress Report
The Delta Water Management Research Unit has had a productive fifth full year. The mission of the unit is to execute research related to agricultural water resources management at the plot, field, farm and watershed scales to further our knowledge base, evaluate technological solutions and inform crop production practices. Much work is at the farm- and field-scale, which requires collaboration with regional producers, organizations and universities (Arkansas State Univ. (ASU), Univ. of Arkansas, and Mississippi State University). Through collaboration and base and grant funds, the program supports 3 scientists, 2 support scientist, 1 program support assistant, and 4 seasonal (LA) employees. Through collaborative agreements the unit works with 3 post-doctoral researchers, 5 full-time technicians, and several summer technicians-both undergraduate and high school students.
Direct grant funding was successfully secured through the Arkansas Cotton Board, Arkansas Rice Research and Promotion Board, Cotton Inc., Ducks Unlimited, and the Natural Resources Conservation Service. Collaboratively the unit has received sub-awards from two Arkansas Soybean Research and Promotion Board grants. The ARS scientists were invited to present at Global Water Security for Agriculture and Natural Resources, International Rice Congress, Arkansas Soil and Water Education Conference, Sino-US Water Savings Technologies Flagship Project, International Congress of Science and Technology in the Tropics, Economics of Managed Aquifer Recharge, and the National Conservation Systems Cotton and Rice Production Conference. The ARS scientists mentored two students in the Bridge the Divide Program and one in the Louis Stokes Alliance for Minority Participation.
All scientists are developing their individual programs while working collectively on unit-wide efforts. Continued progress was made on groundwater/surface water interaction, in-stream water quantity and quality, and water quality of reservoir and tail water recovery irrigation systems. In close collaboration with a local producer, the ARS scientists are measuring water use, water quality, greenhouse gas emissions, soil moisture, grain quality, and/or arsenic levels on production sized rice fields. This effort will be expanded through the Natural Resources Conservation Service’s Groundwater Initiative, whose goal is to materially reduce the cones of depression in Arkansas’ Mississippi River Valley Alluvial aquifer. DWMRU was invited to participate in this 10-year study that will involve working closely with Arkansas producers and other state and federal agencies to increase use of irrigation-conserving technologies and management practices. The DWMRU was asked to lead efforts to measure changes in irrigation use over time in two 50,000-acre study regions. Largely from newly funded research grants in collaboration with ASU, an ARS scientist has begun a new study on irrigation impacts from cover crop use in soybean and cotton production. Through collaboration with RiceTec, Dale Bumpers National Rice Research Center, and ASU, an ARS scientist continues to build upon a database of greenhouse gas emissions by management and variety from the mid-south. Significant progress was made on the development of state-of-the-art field infrastructure and crop establishments of 320 rice diversity panels to assess high night temperature stress tolerance in flooded rice system, which is part of a multi-institutional National Science Foundation project on rice and wheat heat resilience.
Accomplishments
1. On-farm irrigation reservoirs and associated structures have been constructed in Arkansas to help reduce reliance on groundwater. Reservoirs store winter-spring precipitation for later use as crop irrigation and also facilitate reuse of irrigation runoff. Conversely, reservoirs represent significant investments in financial and natural resources, and may cause producers to forego crop production and incur long-term maintenance costs. Thus, an analysis of reservoir construction trends in the Grand Prairie (GP) and Cache River (CR) Critical Groundwater Areas was conducted by ARS scientists in
Jonesboro, Arkansas, to assist in future water management and resource allocations. The objectives were to determine the following for both critical groundwater areas: 1) Numbers and sizes of reservoirs constructed over time, 2) Reservoir locations in relation to saturated aquifer thickness, and 3) Types of land used in reservoir construction and resulting footprints of the reservoirs and associated structures. Between 1996 and 2015, on average, 16 ± 5 and 4 ± 1 reservoirs were constructed per year, corresponding to cumulative new reservoir surface areas of 161 ± 49 and 60 ± 18 ha yr-1, for GP and CR, respectively. In terms of reservoir locations relative to aquifer status, after 1996, 84.5% of 309 reservoirs constructed in GP and 91.0% of 78 in CR were located in areas with remaining saturated aquifer thicknesses of 50% or less. The majority of new reservoirs (74% in GP and 63% in CR) were constructed on previously productive cropland. The disparities in reservoir construction rates, locations, and prior land uses between the two critical groundwater areas is likely due to groundwater declines being first observed in GP as well as the existence of two large-scale river diversion projects under construction in GP that feature on-farm storage as a means to offset groundwater use. Results of this analysis can be used in the development of targeted resource allocation initiatives and conservation efforts in critical groundwater areas and other similarly water-scarce regions.
2. Rice is important to the economies of rice-growing states in the Lower Mississippi River Valley. This rice also relies heavily on groundwater pumped from the alluvial aquifer that is declining in portions of Arkansas and Mississippi. Results from this study by ARS scientists in Jonesboro, Arkansas, show that if producers were to maintain approximately two inches of freeboard to capture rainfall, rice irrigation use can be reduced by 10% relative to when no freeboard is managed. These results can be used to devise simple rice flood management practices that maximize rainfall capture that, in turn, could help alleviate on-going declines in the Mississippi River Valley Alluvial aquifer.
3. Innovative irrigation strategies in rice production that sustain rice quality are paramount to the longevity of production in the US Mid-South, where 75% of US rice is grown. To ascertain the impact of water-saving irrigation practices on rice quality, three irrigation treatments, namely: continuous flooding with cascade delivery; continuous flooding with multiple-inlet delivery; and Alternate Wetting and Drying (AWD) with multiple-inlet delivery were established on production-sized fields in 2017 by ARS scientists in Jonesboro, Arkansas. Milling yields were not affected by irrigation treatments. The average milled rice and head rice yields across irrigation treatments were 73% and 59%, respectively. Rice quality evaluations showed that chalkiness occurred more frequently in the AWD fields (5.6%) than in the two continuously-flooded fields (5.1 to 5.2%). Pasting properties such as peak and breakdown viscosities were not affected by irrigation treatments, but setback viscosity, which is often linked with cooked rice texture, was least for the AWD treatment (146 cP) and similar for the continuously-flooded fields (168 to 169 cP). Producers that are implementing these practices, millers that are receiving rice from different irrigation practices, and industry that must consider different characteristics when using rice in products will all benefit from the findings in this study.
4. Approximately 11% of the global anthropogenic methane emissions are currently attributed to rice cultivation. In this study by ARS scientists in Jonesboro, Arkansas, the impact of water irrigation practices on rice field CH4 emissions was evaluated in Arkansas, where more than half of US rice is produced. Typical rice irrigation uses continuous flooding (CF) during the majority of the production season. While conserving water, the Alternate Wetting and Drying (AWD) irrigation practice can also reduce CH4 emissions through the deliberate, periodic introduction of non-flooded conditions. Continuous measurements of methane flux indicated a 79% reduction in season-long emissions from the AWD field relative to the CF field. The seasonal cumulative carbon losses by CH4 emission were 30.3 and 141.9 kg CH4-C ha-1 for the AWD and CF fields, respectively. Considering differences in field conditions and soils, the AWD practice is attributable to a 36-51% reduction in seasonal emissions. The substantial decrease in CH4 emissions by AWD offers strong evidence for the efficacy of AWD in reducing methane emissions in Arkansas rice production. The AWD practice is under consideration for carbon offsets trading and this new market could encourage greater reductions in methane emissions on a larger scale.
5. Assessment and monitoring of crop type and extent is one of the most critical information needs for food security. Crop type inventory and within season estimates at moderate (<30m) resolution has been elusive in many regions due to lack of temporal frequency, clouds, and restrictive data policies. New opportunities exist from operational fusion of Landsat-8 Operational Land Imager (OLI), Sentinel-2 (A & B), and Sentinel-1 (A & B) which provide more frequent open access observations now that these satellites are fully operational. The goal of this research application by ARS scientists in Jonesboro, Arkansas, was to compare Harmonized Landsat-8 Sentinel-2 (HLS), Sentinel-1 (S1), and combined radar and optical data in an operational, near-real time context. Outcomes show HLS achieved high accuracies and the ability to provide insight on crop location and extent within the crop season. Overall, the growth in availability of time dense moderate resolution data streams and different sensitivities of optical and radar data provide a mechanism for within season crop mapping and area estimates that can help improve food security.
Review Publications
Liang, L., Runkle, B.R., Sapkota, B.B., Reba, M.L. 2019. Automated mapping of rice fields using multi-year training sample normalization. International Journal of Remote Sensing. 40:(18):7252-7271. https://doi.org/10.1080/01431161.2019.1601286.
Torbick, N., Huang, X., Ziniti, B., Johnson, D., Masek, J., Reba, M.L. 2018. Fusion of moderate resolution earth observations for operational crop type mapping. Remote Sensing. 10(7):1-16. http://doi.org/10.3390/rs10071058.
Graham-Acquahh, S., Siebenmorgen, T.J., Reba, M.L., Massey, J., Mauromoustakos, A., Adviento-Borbe, A.A., January, R., Burgos, R., Baltz-Gray, J. 2019. Impact of alternative irrigation practices on rice quality. Cereal Chemistry. 96:815-823. https://doi.org/10.1002/cche.10182.
Massey, J., Smith, M.C., Adviento-Borbe, A.A., Reba, M.L., Avila, L.A. 2019. Using rainfall analysis to manage freeboard and increase rainfall capture for multiple-inlet rice irrigation in the Lower Mississippi River Valley. Journal of Irrigation and Drainage Engineering. 145(8). https://doi.org/10.1061/%28ASCE%29IR.1943-4774.0001403.
