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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

2020 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
Research to improve irrigation efficiency continued under Objective 1. Field research for a deficit irrigated corn silage study was completed during the 2019 growing season. A new study was initiated in 2020 to measure crop water use of sorghum-sudan grass, which is not a typical crop in southern Idaho. Two sorghum-sudan grass varieties were planted in 18 or 76 cm row spacing. Research continued to evaluate establishing alfalfa by interseeding with corn. Results from 2018 and 2019 showed that practice can be successful in southern Idaho, although corn silage yield was 5-10% less when alfalfa was interseeded with the corn compared to corn grown without alfalfa. Initial research showed no benefit to applying a growth regulator to the alfalfa, which is an essential component of the practice in Wisconsin. New research is comparing alfalfa yield established by interseeding with traditional establishment methods of direct seeding alfalfa in the spring or seeding alfalfa after small grain harvest in August. Research to evaluate adoptability of canopy temperature-based crop water stress index (CWSI) as an irrigation management tool for wine grape was conducted at two commercial vineyards in southwest Idaho. Climatic conditions, soil water content, and vine canopy temperature were continuously monitored from July through September in 2019. Climatic and canopy temperature data were used to compute a daily average CWSI based on a cultivar-specific machine learning model that estimated well-watered canopy temperature. The daily average CWSI and soil water content data were published on a website for easy access by the vineyard managers. The vineyard managers readily utilized the website information for making daily irrigation management decisions. Climatic conditions and vine canopy temperature were continuously monitored in wine grape cultivar Malbec irrigated at four rates in an experimental vineyard at Parma, Idaho. The irrigation rates were based on applying 28 mm of water when daily CWSI thresholds of 0.3, 0.4, 0.5 and 0.6 were exceeded. Irrigation amounts applied from June through September were 233, 172, 148 and 68 mm for the 0.3, 0.4, 0.5 and 0.6 irrigation thresholds, respectively. Average weekly leaf water potential decreased with increasing CWSI irrigation threshold, indicating greater plant stress with higher CWSI thresholds. Berry weight, cluster weight and titratable acidity also decreased with increasing CWSI threshold. However, total yield and soluble solids were not significantly different between CWSI irrigation thresholds. Irrigation management based on a daily CWSI threshold was an effective methodology for implementing and maintaining different levels of vine water stress. Climatic conditions and vine canopy temperature were also continuously monitored in wine grape cultivar Pinot noir in a commercial vineyard in southwest Oregon. The results indicate that the methodology developed for estimating wine grape daily CWSI in Idaho is transferable to other regions with different climatic conditions. Research continued to evaluate CWSI-based irrigation scheduling for sugar beet in an arid environment. Climatic conditions and canopy temperature of sugar beet irrigated at four rates were continuously monitored in 2019. The four irrigation rates consisted of applying 100% of estimated evapotranspiration and irrigating when daily CWSI exceeded thresholds of 0.2, 0.4 and 0.6. Irrigation plus precipitation amounts were 649 mm for full irrigation and 467, 370 and 252 mm for the CWSI irrigation thresholds of 0.2, 0.4 and 0.6, respectively. Root and sucrose yield decreased with increasing CWSI irrigation threshold. The relationship between sugar beet daily CWSI and available soil water was also investigated. A general relationship occurred between daily CWSI and total available soil water in the root zone, but it was poorly defined because total available soil water does not describe where soil water is distributed within the root zone. Maximum available soil water of any single 15 cm soil layer, to a depth of 1.8 m, was better correlated with daily CWSI than total available soil water in the root zone. A study continued comparing crop yield and water balance for tilled and no-tilled, cover crop and no cover crop treatments. Berms and flumes were installed to measure runoff that may occur during sprinkler irrigation to better quantify water balances on these plots. Infiltration, aggregate stability, and water holding capacity are also being measured on these plots, and additional long-term studies are being conducted at Kimberly, Idaho, in cooperation with University of Idaho. Research for Objective 2 continued to quantify the impacts of management practices on water quality for irrigated crop production. Water quality and quantity monitoring in the Upper Snake/Rock watershed continued for the Conservation Effects Assessment Project (CEAP). Data were used to determine sediment, soluble salt, and nutrient concentration trends and annual loads of irrigation water flowing into the watershed and returning back to the Snake River. From 2006 to 2018, irrigation return flow sediment, total phosphorus, dissolved phosphorus, soluble salt, and nitrate-nitrogen concentrations were greater than the concentrations in the irrigation water. 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 are being measured on plots where pan lysimeters have been installed. An automated method was developed for using publicly available satellite information to map types of irrigation for identifying 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. An experiment assessing the long-term influence of crosslinked polyacrylamide and polyacrylate amendments (hydrogels) on the status, leaching, and plant uptake of soil nutrients was completed. Soil nutrient data were summarized and analyzed, and a manuscript reporting results was prepared. This study is the first designed to examine long-term benefits of crosslinked polymers in an agricultural setting. The knowledge it provides to the polymer industry and farmers is important because it shows that, if properly managed, hydrogel-amended soils can increase nutrient availability to crops and reduce nitrate nutrient losses in drainage.

1. Long-term solution for thirsty crops is identified. 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 are considered to last less than five years. ARS researchers at Kimberly, Idaho, conducted a nine-year study to measure the effects of a single hydrogel application on plant available water in soil. Based on the slow decline in effectiveness measured in this study, the water retention benefits of hydrogels should last 24–29 years, considerably longer than industry estimates of five years. The long-term water retention benefits substantially increase the cost effectiveness for farmers applying hydrogels to improve water holding capacity in soil.

Review Publications
King, B.A., Tarkalson, D.D., Bjorneberg, D.L. 2020. Soil water extraction patterns and water use efficiency of irrigated sugarbeet under full and limited irrigation in an arid climate. Journal of Sugar Beet Research. 56(3&4):23-53.
Lentz, R.D., Ippolito, J.A., Lehrsch, G.A. 2019. Biochar, manure, and sawdust alter long-term water retention dynamics in degraded soil. Soil Science Society of America Journal. 83(5):1491-1501.
Bjorneberg, D.L., King, B.A., Koehn, A.C. 2020. Watershed water balance changes as furrow irrigation is converted to sprinkler irrigation in an arid region. Journal of Soil and Water Conservation. 75(3):254-262.
Lentz, R.D. 2020. Long-term water retention increases in degraded soils amended with cross-linked polyacrylamide. Agronomy Journal. 112(4):2569-2580.
Baffaut, C., Lohani, S., Thompson, A., Davis, A.R., Aryal, N., Bjorneberg, D.L., Bingner, R.L., Dabney, S.M., Duriancik, L.F., James, D.E., King, K.W., Lee, S., McCarty, G.W., Pease, L.A., Reba, M.L., Sadeghi, A.M., Tomer, M.D., Williams, M.R., Yasarer, L.M. 2020. Evaluation of the Soil Vulnerability Index for artificially drained cropland across eight Conservation Effects Assessment Project watersheds. Journal of Soil and Water Conservation. 75(1):28-41.