Location:2012 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:
Substantial results were realized over the 5 years of the project. Deficit irrigation is an important management practice to sustain irrigated agricultural production with limited water supplies. Accurate water use estimates are critical to managing deficit irrigation. Crop yields in these trials with corn, sunflower, pinto beans, and wheat tended to be linearly related to evapotranspiration water consumption with a negative intercept, such that yield per unit water consumption (water use efficiency) decreased with deficit irrigation. This result implies that deficit irrigation often will not be a good economic choice. A ratio of crop canopy temperature measured over fully irrigated and water stressed corn was determined to be a viable substitute for the traditional water stress coefficient based on soil water parameters and measurements. Estimates of crop water use for deficit irrigated corn using canopy temperature as the stress indicator and canopy reflectance to adjust for anomalies in plant growth compared more favorably to measured crop ET than water use estimates calculated by traditional procedures. These measurements are sensed remotely and can be automated for effective use of the technology. Accurate and practical water use estimates will allow growers to reduce risk involved in deficit irrigation practices and precisely manage limited supplies of irrigation water. The dissipation and movement of herbicides used under deficit irrigation conditions depended on the crop, rainfall, and use patterns. Pendimethalin did not leach in any of the years, where sulfentrazone leached very rapidly in the top 30 cm of the soil column if a heavy irrigation or rainfall occurred soon after treatment. The rate of atrazine dissipation depended on the history of atrazine use. Enhanced atrazine degradation occurred within 8 weeks after application and the soil retained the ability to rapidly degrade atrazine at least 3 years after the herbicide was applied. Decision support systems were released to aid farmers in managing weeds in a cost-effective manner and to help ranchers adjust range management practices based on precipitation records. Our new CRIS project (5402-13000-007-00D) will further evaluate and improve these technologies for managing deficit irrigated corn and sunflower.
1. Yield is linearly related to water consumption. The four years of research on the effect of deficit irrigation (irrigationg less than full crop water requirements) on productivity of corn, sunflowers, dry beans and wheat showed that crop yields tended to be linearly related to evapotranspiration water consumption and that yield per unit water consumption (water use efficiency) decreased with deficit irrigation. This result implies that deficit irrigation often will not be a good economic choice. If a farmer has limited water, it would be better to fully irrigate fewer acres rather than apply limited water over more acres.