Project : USDA ARS

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Research Project: Preserving Water Availability and Quality for Agriculture in the Lower Mississippi River Basin

Location: Delta Water Management Research

2020 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
Objective 1: As part of the Lower Mississippi River Basin LTAR, ARS researchers are measuring water use, water quality, greenhouse gas (GHG) emissions, soil moisture, grain quality, and arsenic levels in rice grain at commercial rice fields. While climate change continues to become a threat to crop production and water resources, innovative technologies associated with rice resilience to high temperature and post-harvest assessment of grain are being investigated by ARS researchers using state-of-the-art infrastructure and instrumentation. Continued field validation of these advanced technologies facilitates the development of rice genomes resilient to climate change. Through collaboration with RiceTec, Dale Bumpers National Rice Research Center, and Arkansas State University (ASU), ARS researchers continue to build upon a database of greenhouse gas emissions by management and variety from the mid-south. Research on the automation of rice irrigation continues and is being conducted on 16 farm fields in Northeast Arkansas. This study compares water savings, yield, economics, and other parameters of fully-automated, partially automated, and fully-manual rice irrigation management. Irrigation research involving the use of winter cover crops in a furrow irrigated rice-soybean system continue at two farm locations while a soybean-maize system is being investigated at two other farm locations in cooperation with the University of Arkansas (U of A) and Natural Resources Conservation Service (NRCS). With the long-term research efforts in the study of water management in rice, ARS researchers received a 2020 Conservation Innovation Award from the Soil and Water Conservation Society for their role in the “Arkansas Rice Irrigation Water Management Field Day”. ARS researchers were invited to present their findings at the Sino-U.S. Water Savings Technologies Flagship Project, National Conservation Systems Cotton and Rice Production Conference, American Chemical Society, Agricultural and Food Chemistry Division National Meeting, Arkansas Chapter of the American Society of Agricultural and Biological Engineers, and a rice producers association in Brazil. Objective 2: Research in this objective has been expanded by the unit’s invited participation in the Natural Resources Conservation Service’s Arkansas Groundwater Initiative (AGWI). This NRCS-funded initiative is a 10-year effort whose overarching goal is to reduce aquifer decline in critical groundwater areas located in the Grand Prairie and Cache River Critical Groundwater Areas (CGA) of Arkansas. The program involves collaborations between farmers and ARS, NRCS and U.S. Geological Survey (USGS) personnel. DWMRU scientists will measure irrigation use before and after a range of conservation practices are employed which USGS staff will try to correlate with any resulting changes in groundwater levels. These activities complement on-going efforts to inventory agricultural surface water resources and irrigation practices in the Cache River GCA that will be used to create potential scenarios for attaining groundwater use reductions. The unit has shifted managed groundwater recharge efforts to infiltration galleries (IG), with plans to test two IG in the Cache River CGA. A manuscript describing the optimal locations for IG in the study area will be submitted in September to a Water Resources Research special section on aquifer decline. We anticipate construction of the IG will begin in September. Objective 3: Much of the work in this objective is at the farm- and field-scale, which requires collaboration. Collaboration to meet this objective continued with regional producers, organizations and universities (ASU, U of A, and North Carolina A&T State University). Data collection at the nine edge-of-field sites and ten in-stream CEAP sites continued. Data from these sites were used to help verify the national Soil Vulnerability Index. New funding was secured through U of A collaborators to continue research at four sites that were at the end of their six-year edge-of-field contract with NRCS, and to begin data collection at two new rice/soybean sites.

Accomplishments
1. Greenhouse gas measurements for mid-South agricultural systems. ARS researchers in Jonesboro, Arkansas, found that when rice fields are re-flooded after harvest to provide winter habitat for waterfowl, methane gas emissions can equal to 20 to 30% of those produced during the rice growing season. Thus, while winter flooding is beneficial to waterfowl and generates needed income for regional economies, it also contributes to the environmental footprint of rice. ARS researchers also found that methane can be reduced by up to 50%, relative to conventional practices when rice farmers use intermittent flooding, a water-conserving irrigation practice. Taken together, these results show that methane emissions created by winter flooding can be offset by careful irrigation management during the rice growing season while protecting grain yield and groundwater resources. These results further improve our understanding of agricultural sources and sinks of greenhouse gas emissions and provide current datasets for estimating US emission factors from rice cultivation.

2. Intensification of grain and cereal production while protecting water and the environment. In the U.S. and Brazil, rice and soybean are grown in rotation on clayey soils that pose both drainage and irrigation challenges to advancing yield while protecting water and the environment. To address these and other issues, land-forming has been practiced in the mid-South U.S. since the 1980s, but is relatively new to Brazilian producers. ARS researchers in Jonesboro, Arkansas, were invited to assist researchers in Brazil and Uruguay to compare land forming options for fields with complex slopes and shapes. Refinements to increase production of grains will be required to meet future demands. ARS researchers in Jonesboro, Arkansas, were requested by a major manufacturer of breakfast cereals to summarize the status of cereal production in the U.S. The chapter offers new insights to develop impactful research studies in advancing yield while protecting water and the environment. Results of these studies can be used by policy makers and extension and research personnel in efforts to address sustainable crop production in the next decade.

3. Long-term water quality measurements at field and farm scales. Knowledge of how production practices affect water quality help land managers and farmers make more informed decisions when implementing soil and water conservation practices. ARS researchers in Jonesboro, Arkansas, found that nutrient and sediment losses that occur outside of the growing season (i.e., winter, spring) were statistically higher than those measured during the growing season, lending support to the need for practices such as winter cover crops and proper use of slotted-board risers during the off-season. Lower concentrations and loads of nutrients and sediment were observed in rice fields compared to measurements made in the cotton and soybean systems. As part of these efforts, an improved method for measuring nitrate in the laboratory was developed that reduced the need for a toxic reagent. These findings (a) help inform regional budgets on nutrient and sediment loss, (b) guide land managers and state conservationists on where to target their limited resources, and (c) may be used to calibrate/verify/validate water quality models.

U.S. DEPARTMENT OF AGRICULTURE

Delta Water Management Research: Jonesboro, AR