Location:2008 Annual Report
1a. Objectives (from AD-416)
OBJECTIVES 1. Develop guidelines, protocols and management strategies for irrigated crop production with limited water supplies. a. Determine crop water production functions and weed, and herbicide response to irrigation amount for a four crop rotation under two tillage practices in the Great Plains. b. Develop remote sensing tools and site-specific strategies to efficiently manage water and nitrogen applications for irrigated cropping systems. 2. Develop tools and strategies for site-specific weed management. 3. Develop tools to assess the impacts of cropping systems and irrigation practices on furrow irrigation-induced erosion.
1b. Approach (from AD-416)
We will use small plot field trials to develop water production functions, weed management strategies, and remotely sensed water deficit measurements of four crops (corn, sunflower, wheat and dry beans) under two tillage systems (conventional tillage and minimum tillage). The effects of tillage and limited irrigation on crop yields, weed population dynamics, and herbicide efficacy will be measured. Deficit irrigations will be scheduled to optimize production using past studies of critical growth stages and crop simulation models. Active and passive sensors on ground-based platforms will measure crop response to water and nitrogen stress. The research will be done in collaboration with an agriculture economist and crop modelers to provide basic information for both short and long-term decisions on the best way to maximize economic return with limited irrigation water. Field measurements and computer simulation studies will be used to determine the utility of site specific weed management in growers' fields. We will contribute to an ARS effort to develop a model for NRCS to assess the impacts of cropping systems and irrigation practices on furrow irrigation-induced erosion.
3. Progress Report
The Limited Irrigation Research Farm (LIRF) was established for conducting trials on limited irrigation and crop growth. A system was installed to provide water on demand to each of the four crops (corn, wheat, sunflower and dry beans). Six irrigation treatments were established for each crop ranging from 40 to 100% of the crop’s maximum water use. An automated weather station was installed to provide data for calculating the maximum crop water uses rates. Detailed measurements of crop growth and soil moisture were made at regular intervals to improve the timing and amounts of irrigation to minimize stress during critical reproductive stages of each crop. Neutron probe access tubes were installed in each plot for soil moisture measurements to a 2 m depth. The soil profile at each tube location was characterized and the neutron probe was calibrated at the time of tube installation. Plant height, intercepted light measurements for canopy cover estimates, and crop phenology were determined through the growing season. Bowen ratio/energy balance instrumentation was installed in two fully irrigated areas planted to corn and beans to measure crop evapo-transpiration (ET). An infrared thermometer (IRT) was also installed to collect canopy temperature data used to determine the degree of plant water stress imposed on a crop due to limited water availability. Soil samples to assess the weed seed populations were collected across the field. The predominant weeds in the seed bank were toothed spurge, purslane and puncture vine and other broadleaf weeds with few grasses. Soil samples were also taken through the growing season from the dry bean and sunflower plots that were treated with metolachlor or a combination of pendimethalin plus sulfentrazone, respectively, to determine the effect of different irrigation patterns on herbicide movement and dissipation. Experiments to evaluate the patterns of weed emergence under limited irrigation were established in corn and sunflower. We are currently investigating a modeling approach that has been used successfully to identify favorable environments for the spread of plants based on sparse and informal information such as herbarium specimens and survey information that federal and state agencies collect about weeds. Simple software was developed that growers can use to estimate weed cover and map weed distribution in fallow fields with images from a color digital camera on moving tractor. The software allows detection of many different weeds under a wide range of conditions. The software will be available at http://arsagsoftware.ars.usda.gov/agsoftware/ in September, 2008. The decision algorithms of our software for site-specific weed management in corn, WeedSite, were programmed so that site-specific weed management can be evaluated for many different crops. The module will be included in a popular farm record-keeping system through a three-way CRADA with the private software company, a corn growers group and the ARS. This progress report relates to NP 211 Action Plan Problem Areas 2.5 (Cropping and Tillage Strategies to Best Use Limited Water Supplies) and 6 (Water Quality Protection Systems).
5. Significant Activities that Support Special Target Populations
Farahani, H.J., Howell, T.A., Shuttleworth, W.J., Bausch, W.C. 2007. Evapotranspiration: Progress in measurement and modeling in agriculture. Transactions of the ASABE. 50(5):1627-1638.