Location:2009 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 first field season of the limited irrigation trials was completed successfully. Good data was collected for the 2008 corn and sunflower crops. Data was collected for the dry beans, but yields were below expectations. Eight varieties of pinto beans were also grown with two levels of irrigation in cooperation with Mark Brick, CSU bean breeder. Water use and water production functions were calculated for the three crops and presented at several workshops and the EWRI meeting. Winter wheat was planted in August 2008 and the remaining three crops were planted in spring 2009. Two wheat variety by water trials were also planted, monitored, and harvested in collaboration with CSU Wheat Breeders and ARS-Agricultural Systems Unit. The 2008 bean variety by water trial was repeated in 2009. Plant physiological and stress response measurements were completed as described in the project plan. Energy balance instrumentation was installed in two corn treatments in collaboration with ARS-ASR and CSU. Neutron probe access tubes were installed in wheat, corn and beans, respectively. Since these tubes were installed in different locations than in 2008, four sites based on soil differences in each of these blocks were used to check the calibration equation for the neutron probe. Bowen ratio/energy balance instrumentation was installed in the wheat ET block in late October 2008 to measure crop ET from shortly after emergence, through dormancy, spring green-up, and the main portion of wheat growth, development, and maturation. Stationary infrared thermometers (IRTs) to continuously measure canopy temperature were installed in four of the six irrigation treatments in two reps of the wheat small plot block to measure differences in canopy temperature related to the irrigation scheme. Canopy temperature, canopy reflectance, 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 as related to the various degrees of plant water stress imposed by the irrigation scheme. Growth stage, plant height, intercepted light for canopy cover estimates, and limited leaf area measurements on corn are in progress for this year’s growing season. These data will be correlated with the remotely sensed data. Studies to investigate the effect of limited irrigation on weed communities were continued at two sites and new studies were initiated to investigate the effect of limited irrigation on seed production and the pattern of emergence and seed production of selected weed species at one location. Testing of the statistical model for predicting weed distributions from presence-only data was delayed but the testing will be more complete and valid for our use of the model. Soil samples were taken from the corn, dry bean and sunflower blocks to determine the effect of irrigation levels on the movement and dissipation of the herbicides applied to the soil of these crops.
1. Evaluation of Center Pivot Irrigation Water Distribution Uniformity. The USDA-Natural Resources Conservation Service requires an independent method to evaluate whether center pivot irrigation systems will perform to their standards before they cost share these systems. A Center Pivot Evaluation Program has been developed and refined over the past 25 years by ARS agricultural engineers in Fort Collins. Although the program has been used by NRCS, several modifications and improvements were needed. The modifications were completed, a user manual written, NRCS engineers were trained to input new nozzle hardware, and the program was turned over to NRCS. This program will enable NRCS to efficiently and accurately assess the predicted distribution uniformity of new center pivots and insure that they meet cost share guidelines. Uniform water distribution will enable efficient irrigation water use by center pivot systems.
2. Enhanced Atrazine Degradation. Herbicide use history is more important than irrigation in determining atrazine dissipation. ARS scientists in Fort Collins, Colorado in cooperation with ARS scientists in Stoneville, Mississippi and scientists at Colorado State University found that herbicide use history and not irrigation or tillage practices was the most important factor in determining the rate of atrazine degradation. Continuous use of atrazine over 4 years led to very rapid dissipation of this herbicide with a concomitant loss of weed control. A survey of soil from over 100 fields in Colorado, California, Mississippi, Florida, Hawaii, Kansas, Illinois, and Hawaii showed that enhanced atrazine degradation is a widespread phenomenon throughout the U.S. where the herbicide is used on a continuous basis. Farmers who depend on the atrazine for residual weed control need to be aware of this phenomenon and will have to change their weed management practices to maintain adequate weed control in crops such as corn and sugarcane.
3. Estimation of Ground Cover of Horticultural Crops with Satellite Imagery. The portion of sunlight that falls on crops is a good indicator of the relative water use of those crops. Measurements were made of ground cover of 16 crops on 30 fields across the 2008 growing season (12 dates) in the west side of the San Joaquin Valley in California. These measurements were compared with Normalized Difference Vegetation Index (NDVI) values from Landsat satellite images. The satellite images estimated ground cover of the wide range of horticultural crops very well. Satellite imagery can efficiently and cost-effectively estimate crop ground cover over wide areas. Accurate ground cover estimates enables improved prediction of crop water use, better irrigation scheduling and more efficient irrigation water use.
Bausch, W.C., Halvorson, A.D., Cipra, J. 2008. QuickBird Satellite and Ground-based Multispectral Data Correlations with Agronomic Parameters of Irrigated Maize Grown in Small Plots. Biosystems Engineering 101 (2008), pp. 306-315 DOI information: 10.1016/j.biosystemseng.2008.09.011