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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Research Project #432376

Research Project: Improving Water Use Efficiency and Water Quality in Irrigated Agricultural Systems

Location: Northwest Irrigation and Soils Research

2021 Annual Report

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.

Progress Report
For Objective 1, progress was made to better understand irrigation requirements for silage corn and sorghum-sudangrass, to investigate a new furrow irrigation erosion prediction method, and to quantify differences in irrigation runoff between tilled and no-tilled plots. Seasonal soil water changes, evapotranspiration and corn yield were analyzed for a multi-year water and nitrogen deficiency study. Four irrigation rates (100, 75, 50 and 25 percent of estimated evapotranspiration) and two nitrogen rates (246 and 0 kg N/ha) were used in the field study. Seasonal soil water extraction and evapotranspiration were significantly different between years and irrigation treatments, but not between nitrogen treatments. This indicates that lower yielding areas in fields will require as much irrigation as higher producing areas. The significant differences between years were due to limited and variable non-growing season precipitation between years. Grain yield was significantly different between years, irrigation treatment and nitrogen treatment. The significant difference in grain yield between years was due to yearly differences in soil water recharge and yield reduction associated with growing corn continuously for three years. The relationship between grain yield and evapotranspiration was nonlinear for both nitrogen treatments, indicating that the yield response for each unit of irrigation water applied decreases as the amount of water applied approaches maximum evapotranspiration. Evaluation of crop water stress index (CWSI)-based irrigation scheduling for sugar beet was initiated but then terminated due to poor sugar beet emergence, possibly due to herbicide carryover. The sugar beet plant population was insufficient for the research study and the study was continued in 2021. An investigation was initiated into using self-organizing maps (SOM) for estimating sediment loss from furrow irrigation. Results show that sediment loss prediction was more accurate using SOM than using a feed forward artificial neural network. The correlation coefficient between measured and predicted sediment loss was greater than 0.9. The greater SOM prediction performance was attributed to the ability of SOM to accommodate highly variable data that is typical of sediment loss from furrow irrigated fields. A study was initiated to investigate yield and water use of sorghum-sudangrass grown for forage. Some Idaho dairymen want to include a warm season crop, like sorghum-sudangrass, as an option for their crop rotation but no production data are available in Idaho. Initial forage yield results from 2020 were about half of typical corn silage yield when sorghum-sudangrass was planted in early June, which is six weeks later than typical planting date for corn. A study continued comparing crop yield and water balance for tilled and no-tilled, cover crop and no cover crop treatments. The field was planted to sugar beet in 2021. No-till plots have had no runoff during 25-mm irrigations with the linear-move irrigation system. Runoff from the tilled plots has resulted in lower soil water content compared to the no-till plots. Cover crop has not impacted runoff or crop yield. Research for Objective 2 continued to quantify the impacts of management practices on water quality. Water quality and quantity monitoring in the Upper Snake/Rock watershed continued for the Conservation Effects Assessment Project (CEAP). Twenty monitoring sites were added in 2021 in cooperation with the Twin Falls Canal Company. From 2006 to 2018, concentrations of sediment, total phosphorus, dissolved phosphorus, soluble salt and nitrate-nitrogen were greater in irrigation return flow than in in the irrigation water initially diverted from the Snake River. However, there were decreasing trends for total phosphorus, dissolved phosphorus and soluble salt concentrations in the return flow. Since most of the irrigation water is used by crops in the watershed, the total amount of sediment and phosphorus entering the watershed with irrigation water each year was greater than the amount returning to the Snake River. However, the data also indicate that nitrate-nitrogen concentrations in shallow groundwater are increasing. One of the main conservation practices implemented in this CEAP watershed is conversion from furrow to sprinkler irrigation. Leaching and irrigation efficiency for furrow and sprinkler irrigation continue to be measured on plots where pan lysimeters have been installed. Initial data indicate that similar or greater amounts of water leached with sprinkler irrigation compared to furrow irrigation. Nitrate-nitrogen concentrations decreased with time for both sprinkler and furrow irrigation. An automated method was developed to use satellite information for mapping types of irrigation to identify where and when sprinkler irrigation was installed in the CEAP watershed. The method uses publicly available satellite images and computer vision to identify sprinkler and furrow irrigated fields. The methodology will be evaluated by comparing remote sensing results with field observations.

1. Conservation practices improve water quality in an irrigated watershed. The Twin Falls Canal Company has been diverting water from the Snake River to irrigate 200,000 acres of crop land since 1905. This project was almost entirely furrow irrigated until farmers began converting to sprinkler irrigation in the 1990s. ARS researchers in Kimberly, Idaho, documented the chronic problem of soil loss from furrow irrigated fields and the dramatic improvement in water quality resulting from converting to sprinkler irrigation, installing edge-of-field sediment ponds and constructing large water quality ponds on irrigation return flow streams. In 1971, 42,000 tons of sediment were discharged to the Snake River. In 2016, more sediment entered the watershed with irrigation water than returned to the Snake River so the irrigation project removed more than 10,000 tons of sediment from the river. Continued conversion from furrow to sprinkler irrigation and improved irrigation management will further reduce sediment and nutrient contributions to the Snake River.

Review Publications
Lentz, R.D., Bautista, E., Koehn, A.C., Sojka, R.E. 2020. Infiltration and soil water distribution in irrigation furrows treated with polyacrylamide. Transactions of the ASABE. 63(5):1451-1464.
King, B.A., Shellie, K., Tarkalson, D.D., Levin, A.D., Sharma, V., Bjorneberg, D.L. 2020. Data-driven models for canopy temperature-based irrigation scheduling. Transactions of the ASABE. 63(5):1579-1592.
Bjorneberg, D.L., Ippolito, J.A., King, B.A., Nouwakpo, S.K., Koehn, A.C. 2020. Moving toward sustainable irrigation in a southern Idaho irrigation project. Transactions of the ASABE. 63(5):1441-1449.
Koehn, A.C., Bjorneberg, D.L., Malone, R.W., Leytem, A.B., Moore, A., Ma, L., Bartling, P.N. 2021. Simulating soil nitrogen fate in irrigated crop production with manure applications. Science of the Total Environment. 793. Article e148510.
Shellie, K., King, B.A. 2020. Application of a daily crop water stress index to deficit irrigate Malbec grapevine under semi-arid conditions. Agriculture. 10(11). Article 492.
King, B.A., Tarkalson, D.D., Sharma, V., Bjorneberg, D.L. 2020. Thermal crop water stress index base line temperatures for sugarbeet in arid western U.S. Agricultural Water Management. 243.
King, B.A., Stark, J.C., Neibling, H. 2020. Potato irrigation management. In: Stark J., Thornton M., Nolte P., editors. Potato Production Systems. Cham, Switzerland: Springer. p. 417-446.
Lentz, R.D., Ippolito, J. 2021. Cross-linked polymers increase nutrient sorption in degraded soils. Agronomy Journal. 113(2):1121-1135.