Submitted to: Irrigation Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2012
Publication Date: 11/2/2012
Citation: Oshaughnessy, S.A., Evett, S.R., Colaizzi, P.D., Howell, T.A. 2012. Automating prescription map building for VRI systems using plant feedback. Irrigation Association Conference Proceedings. November 2-6, 2012, Orlando, Florida. 2012 CDROM
Interpretive Summary: Variable rate irrigation refers to applying variable amounts of irrigation to different locations within a field, and can be achieved through speed or zone control. Zone control variable rate irrigation sprinkler systems are capable of applying varying amounts of irrigation radially and in the direction of travel. Typically, an initial prescription map is built based on soil texture or soil electrical conductivity (EC) and uploaded to the control panel of the sprinkler system to control irrigations. Producers are beginning to update prescription maps within a growing season based on soil water sensing data. However, few studies use plant feedback systems to update prescription maps. This study uses an array of wireless infrared thermometers mounted on a center pivot lateral and an integrated crop water stress index to spatially monitor crop water stress in forage sorghum in the Texas Panhandle Region and control irrigations based on varying thermal stress threshold levels. This preliminary study indicated that it is feasible to construct and upload dynamic prescription maps to the pivot control panel using a combination of USDA-ARS and proprietary coding. As of the soft dough stage, plant biophysical measurements are not significantly different; however, the manual irrigations have received a higher amount of irrigations.
Technical Abstract: Prescription maps for commercial variable rate irrigation (VRI) equipment direct the irrigation rates for each sprinkler zone on a sprinkler lateral as the lateral moves across the field. Typically, these maps are manually uploaded at the beginning of the irrigation season; and the maps are based on prior yield, soil texture, topography, or soil electrical conductivity data. Producers are now beginning to make changes to their initial maps during the growing season based on visual observations, aerial imagery, and/or soil moisture sensors. In this study, plant feedback monitoring with infrared thermometers mounted on a moving sprinkler irrigation system was used to develop dynamic daily prescription maps for VRI sprinkler systems to aid in site-specific irrigation delivery. It was hypothesized that the plant feedback response can be used for site-specific control of crop water use efficiency. Here we discuss the application of a plant feedback algorithm combined with a variable rate irrigation system to implement site-specific irrigation management of sorghum throughout a growing season, and preliminary results to include examples of daily prescription maps, crop biophysical responses, and the average soil water content for the different irrigation treatments grouped by irrigation method. The methods used in this study provide one possible framework for establishing and integrating dynamic prescription maps into automatic control of irrigation scheduling.