Location:2011 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
This progress report relates to NP Problem area #2.5: Cropping and Tillage Strategies to Best Use Limited Water Supplies and Problem area #6: Water Quality Protection Systems. The third field season of the limited irrigation trials was completed. Good data were collected for corn, dry bean, sunflower and wheat. Winter wheat was planted in September 2010 and the remaining three crops were planted in spring 2011. Canopy reflectance, canopy temperature, and images were taken in all plots at least weekly from a boom-mounted platform on a high-clearance tractor to monitor crop growth and development related to the various degrees of plant water stress. Crop growth stage and plant height were recorded, and intercepted light by the crop canopy measured. Bowen Ratio Energy Balance (BREB) instrumentation was installed in two sunflower fields (one fully irrigated the other deficit irrigated) and in a fully irrigated wheat field to measure crop evapotranspiration (ET). Instrumentation was installed in each sunflower field to measure canopy temperature, intercepted light, soil moisture, and obtain images throughout the day to monitor crop response related to the irrigation scheme. Canopy temperature was also measured in wheat. Stationary infrared thermometers (IRTs) were installed in four of the six irrigation treatments in the corn small plots to detect canopy temperature differences. An analysis of 2008-2010 growing season data showed that the ratio of canopy temperature from water stressed corn to the canopy temperature of fully irrigated corn is a useful water stress indicator for estimating crop ET. Stationary IRTs were installed in selected irrigation treatments of corn, sunflower, and wheat in 2011 to obtain canopy temperature data for evaluation of the water stress indicator in additional crops. Analysis of the fate of atrazine and metolachlor in corn, flumioxazin and pendimethalin in dry beans and sulfentrazone and pendimethalin in sunflower was completed. There are clear differences in movement among these herbicides in the soil. Sulfentrazone leaches very rapidly after a heavy rainfall or irrigation in these sandy, high pH soils. Soil microbes that can rapidly degrade atrazine develop within 4 weeks after application of atrazine onto wheat stubble and persist into the next season. Analysis of 2009 and 2010 data to predict potential weed problems in limited irrigation crops indicates deficit irrigation extends the period of emergence of barnyardgrass and reduces seed production of lambsquarters. Late emerging barnyardgrass may be difficult to control in some limited irrigation crops. In contrast, seed production of lambsquarters was not reduced enough to anticipate fewer problems with this weed in limited irrigation crops. Two spreadsheets were developed to sustain agriculture when water is limited. One is a tool to help growers evaluate profit and water use with combinations of full and limited irrigation crops, dryland crops and rotational fallow. The other is a tool to adapt the ARS Drought Calculator, a decision tool to manage forage production under drought, to more areas of the country.
1. Water use estimates for deficit-irrigated crops. 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. ARS scientists in Fort Collins, CO, determined that the ratio of crop canopy temperature measured over fully irrigated and water-stressed corn is a viable substitute for the traditional water use estimates based on the soil water measurements. Crop canopy measurements can be automated and may be able to be sensed remotely, enabling 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 irrigation water.
2. Predicting the risk of herbicide resistant weeds in a farmer’s field to motivate prevention. The rapid development and spread of herbicide-resistant weeds suggests growers underestimate the risk of resistance or view the future risk as low compared the cost of prevention. In contrast, land managers react promptly and effectively to invasive weeds by identifying vulnerable areas with species distribution modeling. We tested the use of this method for predicting the risk of herbicide resistance in a farmer’s field. Risk can be estimated from limited presence-only data rather than expensive surveys to identify many fields with and without the resistant weed. Preliminary results with glyphosate resistant horseweed in corn and soybean fields point towards providing risk estimates that will motivate growers to use preventative strategies and eliminate ineffective use of herbicides.
Bausch, W.C., Trout, T.J., Buchleiter, G.W. 2010. Evapotranspiration Adjustments for Deficit Irrigated Corn Using Canopy Temperature: A Concept. Journal of Irrigation and Drainage. Irrigation and Drainage (wileyonlinelibrary.com) DOI:10.1002/ird.601.