Location: Northwest Irrigation and Soils Research
2017 Annual Report
Objectives
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.
Approach
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
This report documents progress for project 2054-13000-009-00D, "Improving Water Use Efficiency and Water Quality in Irrigated Agricultural Systems," which started in December 2016 and continues research from Project 2054-13000-008-00D Soil and Water Conservation for Northwestern Irrigated Agriculture.
A three-year study was initiated to measure silage corn yield and forage quality with four irrigation levels (100, 75, 50 and 25% of estimated evapotranspiration). An ongoing study measured canopy temperatures of sugar beet under three irrigation levels (100, 65 and 35% of estimated evapotranspiration). Multiple linear regression and neural network modeling were evaluated for predicting well-watered sugar beet canopy temperature for calculating crop water stress index. Multiple linear regression using solar radiation, air temperature, relative humidity and wind speed as independent variables provided good estimates of well-watered sugar beet canopy temperature. Neural network modeling using the same independent variables, however, predicted well-watered sugar beet canopy temperature with significantly less error than multiple linear regression. Non-transpiring canopy temperature was estimated from the cumulative probability distribution of the difference between measured canopy temperature of the lowest irrigation treatment (driest) and air temperature. Air temperature plus 10 degrees Celsius provided a good estimate of non-transpiring sugar beet canopy temperature. Crop water stress index calculated using these methods detected differences in crop water stress of the deficit irrigation treatments.
Canopy temperatures of six wine grape cultivars were measured under three irrigation levels (100, 70 and 35% of estimated evapotranspiration). A wireless network was developed to monitor canopy temperature of four wine grape cultivars under the three irrigation treatments. Data collected by the wireless network was used to calculate 15-minute average crop water stress index values in real time from 1:00 to 3:00 p.m. A daily average crop water stress index was calculated as the average of 15-minute crop water stress index values between 1:00 and 3:00 p.m. The daily crop water stress index readily detected differences in crop water stress associated with the three irrigation treatments and was used to adjust irrigation scheduling of the full irrigation treatments.
Monitoring of the Upper Snake Rock watershed in Idaho for the Conservation Effects Assessment Project (CEAP) continued. Nitrate enters irrigation return flow from subsurface drain tunnels (essentially man-made springs) in the watershed. While nitrate concentrations in irrigation return flow streams doubled from 1970 to 2005, current trends indicate that concentrations are steady or decreasing, and the amount of subsurface drainage is decreasing which means that less nitrate is being transported to return flow streams. The conversion from furrow irrigation to sprinkler irrigation may be a reason that flow from drainage tunnels has decreased.
An initial study demonstrated that water-soluble polyacrylamide (PAM) treatments could reduce sediment and nutrient losses from pots in commercial nurseries. A second study was initiated to confirm the efficacy of these treatments as well as the effects on plant characteristics of flowers growing in nursery containers. An experiment assessing the long-term influence of crosslinked polyacrylamide amendments on soil water drainage, nutrient leaching, and plant nutrient uptake continued during 2017. Results indicate that crosslinked (or water absorbing) PAM is still reducing leaching from soil in 3.5 gallon pots five years after application.
An informal cooperative project continued with the Shoshone Bannock Tribes in Fort Hall, Idaho, to collect deep soil samples in the spring and after harvest. Elevated nitrate concentrations were not detected below the root zone in these sandy soils. Some samples had elevated phosphorus concentrations below three feet, which could indicate that leaching is occurring and nitrate leached below the six foot sampling depth.
Accomplishments
1. Strip-tilling sugar beet reduces tillage costs and improves infiltration without sacrificing sugar yield. About half of U.S. sugar production comes from sugar beet. Farmers often do several tillage operations before planting because sugar beet seed is small and planted very shallow. ARS researchers in Kimberly, Idaho, compared sugar beet production with strip tillage and conventional tillage under full and deficit irrigation. Sugar yields were similar for both tillage practices under all irrigation amounts, which were applied with a linear move irrigation system. Conventional tillage, however, had 4 to 14% of the irrigation water runoff compared to no runoff from strip tillage. Using strip tillage can reduce production costs $50 to $75 per acre and increase irrigation efficiency while maintaining sugar beet yield.
2. Real-time calculation of crop water stress index for wine grapes. Wine grapes are intentionally water stressed to induce desirable qualities in the berries, but few techniques are available to actively manage water stress without laborious plant monitoring. A wireless network monitored canopy temperatures and calculated crop water stress indexes of four wine grape cultivars under the three irrigation treatments. Crop water stress index was automatically posted on a website where it could be used to guide irrigation. The daily crop water stress index values readily detected differences associated with the three irrigation treatments, and can be used to actively manage water stress in vineyards.
3. Sprinkler irrigation improves soil quality of historically eroded furrow irrigated fields. Converting from furrow irrigation to sprinkler irrigation eliminates the continual erosion of topsoil from the inflow ends of furrow irrigated fields that can reduce crop yields up to 25%. ARS scientists at Kimberly, Idaho, and Ames, Iowa, measured soil quality indicators on paired furrow and sprinkler irrigated fields in the Upper Snake Rock Watershed in Idaho as part of the Conservation Effects Assessment Project. Soil quality index scores were greater on eroded areas of fields that had been converted to sprinkler irrigation compared to fields that were still furrow irrigated. Converting to sprinkler irrigation not only reduces erosion and improves irrigation efficiency, it also improves soil quality of historically eroded areas of furrow irrigated fields, potentially increasing crop yields.
Review Publications
Tarkalson, D.D., King, B.A. 2017. Effects of tillage and irrigation management on sugarbeet production. Agronomy Journal. 109(5):2396-2406. doi:10.2134/agronj2016.09.0530.
Tarkalson, D.D., King, B.A. 2017. Effect of deficit irrigation timing on sugarbeet. Agronomy Journal. 109(5):2119-2127. doi:10.2134/agronj2017.01.0061.
King, B.A., Tarkalson, D.D. 2017. Irrigated sugarbeet sucrose content in relation to growing season climatic conditions in the northwest U.S. Journal of Sugar Beet Research. 54(1&2):60-74.
