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Optimizing Agricultural Water Use and Management

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The ARS Watershed and Water Availability research program develops solutions that improve water management for efficient agricultural production. In the United States, irrigated agriculture produces 49 percent of U.S. crop market value on 18 percent of cropped lands. However, agriculture is subject to growing competition for water resources, growing pressure to safeguard water quality, and a clear need to adapt to alternative water resources. The following FY 2020 research accomplishments highlight ARS advancements in irrigation, drainage technology, and decision support systems for addressing the challenges associated with agricultural water use.

Sub-surface drip reduces seasonal irrigation applications for corn. In the face of declining water supplies, crop farmers need to maximize the yield per unit of water used in crop production, the so-called crop water productivity (CWP). It is not well understood how irrigation application methods affect CWP. ARS scientists in Bushland, TX, compared the water use and yield of grain corn and sorghum production using sprinkler and subsurface drip irrigation (SDI) methods. Using the SDI application method, loss of water to evaporation was reduced by 2-5 inches during the growing season, compared to losses that occurred with sprinkler irrigation. SDI reduced overall corn water use by up to 6 inches and increased grain yields by up to 20 percent. The combined effects were an increase in CWP by up to 46 percent, compared with sprinkler irrigation. The increases in CWP are enough to offset the higher costs for SDI installation.

Deficit irrigation saves water in peach production under arid conditions. Agricultural irrigation is a major user of fresh water in arid and semiarid areas of the world. About 23,000 hectares of peaches grown in the Central Valley of California depend on irrigation, which uses scarce water resources. Deficit irrigation is a potential strategy to save water without severely impacting crop production; however, the long-term impact of deficit irrigation on productivity is not well understood. ARS researchers in Parlier, CA, demonstrated in a 10-year field study that deficit irrigation can result in up to 40 percent water savings without significant yield losses or reductions in fruit quality such as firmness, total soluble solids, pH, malic acid, or total phenolics. Findings from this long-term research provide peach growers an alternative irrigation strategy to save water and lower input costs.

A long-term solution for thirsty crops. A cost-effective means of increasing plant-available water can alleviate water stress from infrequent precipitation or limited irrigation supplies. Polymer hydrogels increase the capacity of soil to hold water, but the effects were previously thought to last only a few years. ARS researchers in Kimberly, ID, conducted a 9-year study to measure the effects of a single hydrogel application on plant-available water in soil. Based on the slow decline in water availability seen in this study, the water retention benefits of hydrogels should last from 24 years to 29 years, considerably longer than current industry estimates. The long-term water retention benefits substantially increase the cost effectiveness for farmers applying hydrogels to improve soil’s water holding capacity.

Center pivot mounted leaf temperature sensors are inexpensive and provide accurate input to irrigation water optimization. In times of low crop prices, farmers need to produce crops as inexpensively as possible. One way farmers can reduce input costs is to irrigate only when it is most needed. Crop leaf temperatures are easily measured by sensors, which provide a real-time assessment of water stress, and in turn, indicate if irrigation should be scheduled. However, users of temperature sensors have been concerned that measurements from sensors mounted on a center pivot may not be as accurate as non-moving (stationary) sensors. ARS scientists in Bushland, TX, compared irrigation scheduling based on data from stationary temperature sensors to those mounted on a center pivot. There were no differences in accuracy between stationary or moving temperature sensors, and irrigation application scheduling governed by one type of sensor was similar to scheduling governed by the other. Center pivots are now used on 30 million acres in the United States. Installing temperature sensors aboard center pivots and using them for irrigation scheduling could save farmers substantial water and reduce energy input costs.