2013 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 in 2012 to carry out the current project. This project focuses on developing irrigation schedules that will reduce water consumption while maintaining yield. The first field data collection season was completed successfully in 2012 with high yields under full irrigation in spite of extreme drought conditions. Plant growth and phenology, canopy temperature, shoot and root growth and development, as well as gas exchange and metabolite levels, were measured throughout the growing season along with soil water content and atmospheric evaporative demand to determine what factors are most important in the plant’s response to water stress and yield. Minirhizotron access tubes were installed and root growth monitored. Sap flow gauges were installed to monitor water uptake of individual plants. The gauges show great promise, but also proved to be difficult and time consuming to install and maintain. Water balance data and evapotranspiration estimates were completed for the 2012 season. Additional years of data will be required to draw conclusions.
The final year of trials with an experimental ethylene inhibitor was carried out with inconclusive results.
The second year of field experimentation was initiated (2013 season). New instrumentation for the high boy reflectance tractor was purchased and installed including radiometers and an infrared camera. A greenhouse pot study was carried out to validate the sap flow gauge measurements and to determine critical differences between stress response in corn and sunflower. An unexpected weather event during a critical period (May snow) prevented successful completion of the experiment.
Due to retirements and a shortage of personnel, the water production function database and risk analysis (Obj.
3)could not be completed.
Glyphosate resistant weeds are becoming an increasingly greater problem for growers in multiple crops. Rapid identification of glyphosate resistant weeds is critical for managing this problem. A field assay was developed by ARS researchers in Ft. Collins, CO in cooperation with Monsanto that potentially could provide a visual method for detecting glyphosate resistance. This assay detects the presence of shikimate, a metabolite that accumulates in susceptible plants but not in glyphosate resistant plants. With this rapid assay, glyphosate resistant weeds can be identified and alternative weed control methods used to control resistant infestations.
Melton, F., Johnson, L., Lund, C., Pierce, L., Michaelis, A., Hiatt, S., Guzman, A., Adhikari, D., Prudy, A.J., Rosevelt, C., Votava, K., Trout, T.J., Temesgen, B., Frame, K., Sheffner, E., Nemani, R. 2012. Satellite irrigation management support with the terrestrial observation and prediction system: A framework for integration of satellite & surface observations to support improvements in agricultural water resource management. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 5(6): 1709–1721.
Anothai, J., Soler, C., Green, A., Trout, T.J., Hoogenboom, G. 2013. Evaluation of two evapotranspiration approaches simulated with the CSM-CERES-Maize model under different irrigation strategies and the impact on maize growth, development and soil moisture content for semi-arid conditions. Agricultural and Forest Meteorology. 176: 64-76.
DeJonge, K.C., Ascough II, J.C., Andales, A.A., Hansen, N.C., Garcia, L.A., Ababi, M. 2012. Improving evapotranspiration simulations in the CERES-maize model under limited irrigation. Agricultural Water Management (2012), pp. 92-103.
Taghvaeian, S., Chavez, J.L., Bausch, W., Dejonge, K.C., Trout, T.J. 2013. Minimizing instrumentation requirement for estimating crop water stress index and transpiration of maize. Irrigation Science. 32:53-65.