2012 Annual Report
1a.Objectives (from AD-416):
1. Quantify crop physiological and yield response to water stress at different growth stages.
2. Develop real-time crop coefficients based on canopy temperature and reflectance for irrigation scheduling.
3. Determine and quantify and understand the causes of variability in crop water productivity to improve yield predictions and decision making.
4. Determine the dissipation and movement of herbicides applied to soil under deficit irrigation.
1b.Approach (from AD-416):
Irrigated agriculture plays a critical role in meeting global food needs. Declining irrigation water supplies threaten the sustainability of irrigated agricultural production in the Great Plains, the U.S. and worldwide. Projected increases in temperature, evaporation, and drought frequency with climate change magnify this concern. The aim of this research is to provide fundamental information and tools to optimize crop production with deficit irrigation and sustain irrigated agriculture under limited water supply. Deficit irrigation supplies less water than crops need to maximize yields, with the goal to increase net returns per unit of water. However, mechanisms of crop response and water savings under deficit irrigation remain poorly understood. We will determine the effect of timing and severity of deficit irrigation on evapotranspiration, crop physiological response, and crop productivity using corn and sunflower as models. With this information, we will develop recommendations on how to time irrigations to maximize crop yield per unit water consumed and allocate limited irrigation on a farm. We will also develop a method to schedule deficit irrigation using measurements of crop ground cover and canopy temperature. As part of a multi-location project, we will develop methods to apply experimental results like ours throughout the western U.S. and areas of the world facing similar threats. We also will ensure that weeds will not hinder deficit irrigation success by determining the herbicide efficacy and environmental impacts in these systems.
The field plots were reorganized and the irrigation system was modified to begin a new research project that is an extension of a recently completed research project. The new research project will focus on developing irrigation schedules that will reduce water consumption while maintaining yield. Canopy temperature, soil moisture levels, shoot and root growth and development, as well as gas exchange and metabolite levels, are being measured throughout the growing season to determine what factors are most important in the plant’s response to water stress and yield. Estimates of crop evapotranspiration (ET) for fully irrigated corn, sunflower, and wheat based on data from our previous research project are being developed and compared to estimates from other locations to determine the transferability of these estimates from one location to another. In addition, plant measurements such as percent ground cover and vegetation indices calculated from canopy reflectance in the red and near infrared regions of the electromagnetic spectrum are being investigated as inputs to insure that the crop coefficient used for estimating crop ET accurately reflect plant growth conditions in the field for both fully- and deficit-irrigated crops.
Sulfentrazone leaches rapidly in sandy soil with high pH. Two years of research comparing the movement of pendimethalin and sulfentrazone applied to a sandy soil, pH 8, in sunflowers showed the two herbicides behave quite differently. Pendimethalin did not move below the top 7.5 cm of the soil in either year or irrigation frequency. Sulfentrazone, however, moved in the top 30 cm of the soil and the rate and amount of movement was directly related to the amount and intensity of irrigation or rainfall. Sulfentrazone moved rapidly downward in the soil profile when 30 to 50 mm of rainfall/irrigation was applied and remained in the lower profile for the rest of the season. These results support the label for sulfentrazone which warns that the herbicide can cause crop damage if applied to a sandy soil with high pH.
Hunter, W.J., Shaner, D.L. 2012. Removing hexazinone from groundwater with microbial bioreactors. Current Microbiology. 64:405-411.
Islam, A., Ahuja, L.R., Garcia, L.A., Ma, L., Anapalli, S.A., Trout, T.J. 2012. Modeling the impacts of climate change on irrigated corn production in the central Great Plains. Agricultural Water Management. 110:94-108.
Shaner, D.L., Brunk, G., Nissen, S., Westra, P., Chen, W. 2012. Role of soil adsorption and microbial degradation on dissipation of mesotrione in plant available soil water. Journal of Environmental Quality. 41:170-178.
Johnson, L.F., Trout, T.J. 2012. Satellite-assisted monitoring of vegetable crop evapotranspiration in California's San Joaquin Valley. Remote Sensing. 4:439-455.