Location: Northwest Irrigation and Soils Research
Project Number: 2054-13000-009-00-D
Project Type: In-House Appropriated
Start Date: Dec 6, 2016
End Date: Dec 5, 2021
The research in this project includes a series of studies conducted under two broad objectives of improving water use efficiency and water quality in irrigated crop production. Water use efficiency research focuses on a variety of crops and conditions that occur in the northwestern U.S. Much of the water quality research focuses on the Upper Snake Rock (USR) watershed which is part of the ARS Conservation Effects Assessment Project (CEAP). Objective 1: Improve irrigation water use efficiency by improving irrigation scheduling, infiltration, and soil water holding capacity. Subobjective 1A. Quantify silage corn yield and water use under full and deficit irrigation strategies. Subobjective 1B. Develop and test cultivar specific models for calculating crop water stress index (CWSI) as a tool for irrigation management of wine grape in the arid western U.S. Subobjective 1C. Develop and test a CWSI methodology for deficit irrigation management of sugar beet in an arid environment. Subobjective 1D. Compare soil water balances among tilled and no-tilled, cover crop and no cover crop treatments. Objective 2: Quantify the impacts of management practices on water quality for irrigated crop production at field and watershed scales. Subobjective 2A. Determine annual water balances and nitrate losses in the USR watershed. Subobjective 2B. Determine field-scale furrow irrigation efficiency and sediment and phosphorus losses. Subobjective 2C. Measure leaching under sprinkler and furrow irrigated plots with pan lysimeters. Subobjective 2D. Determine the long-term (5+ years) influence of crosslinked polyacrylamide amendments on soil water drainage, nutrient leaching, and plant nutrient uptake. Subobjective 2E. Develop a simple and inexpensive water-soluble polyacrylamide technology to mitigate sediment and nutrient discharges from horticulture potting soil and nursery beds. Subobjective 2F. Evaluate deep soil sampling as an indicator of nitrate leaching in production fields.
The overall objective of improving irrigation water use efficiency will be addressed through four field studies. A three-year study will be to measure silage corn yield response to four irrigation levels ranging from full irrigation to 25% of full irrigation. Full irrigation is defined as no water stress based on soil water measurements. A second study will develop models for calculating the crop water stress index (CWSI) for specific wine grape cultivars so the CWSI can be used to manage deficit irrigation. The CWSI is calculated from actual canopy temperature and the temperatures of well-watered and severely water stressed crop canopies. The models will be used to predict well-watered and severely stressed canopy temperatures so that vineyards will not need to provide these growing conditions to use the CWSI. A third study will collect canopy temperature data from deficit irrigated sugar beet to apply the CWSI technique to this crop. Previous research has shown that sugar beet yield is not significantly decreased when irrigation is reduced about 20%. Canopy temperature measurement could be a convenient method for managing this deficit irrigation. The fourth study will compare water use between tilled and no-tilled plots with and without a cover crop planted after the main crop is harvested. Additional residue from no-till and cover crop can reduce soil evaporation, however, cover crops will require additional irrigation in an arid region. The second objective will be accomplished through watershed, field, and small plot scale research. Watershed and field scale research will measure the changes in water quality as fields are converted from furrow irrigation to sprinkler irrigation. Irrigation water diverted into the 82,000 ha Upper Snake Rock watershed and water returning to the Snake River in eight return flow streams will be monitored for water quantity and quality to determine water, sediment and nutrient balances for the watershed. Similar monitoring will be done at farm and field scale to provide more detailed measures of irrigation efficiency and sediment and phosphorus losses. A separate study will use pan lysimeters in replicated plots to compare leaching and irrigation efficiency between furrow and sprinkler irrigation. Small-scale field studies will be conducted to evaluate the effectiveness of water-soluble polyacrylamide to reduce nutrient losses from nursery container production and water-absorbent polyacrylamide to improve long-term (5 years) water holding capacity in soil. A final study will assess post-harvest, deep soil sampling techniques as an indicator of nitrate leaching. Some agencies are promoting post-harvest deep soil sampling to evaluate nutrient management. However, sampling at a single point in time does not provide sufficient information to judge if leaching has occurred or will occur. Therefore, soil cores will be collected in the spring and fall for 2.5 years to determine if consistent patterns occur in nitrogen and phosphorus concentration profiles in the soil.