Water Resources Research Act Program

Details for Project ID 2016WA412B

Low Energy Precision (/Spray) Applications: Unmanned Aerial System based Rapid Evaluation for Crop and Site Specific System Adaptation in the Pacific Northwest

Institute: Washington
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $27,500 Total Non-Federal Funds: $55,062

Principal Investigators: Lav Khot, Troy Peters

Abstract: co-PIs: Peters, R. Troy. 1; Neibling, William H.2 Water is one of the key input resources in the irrigated crops production. Amongst the various irrigation methods used in the Pacific Northwest, overhead sprinkler irrigation through central pivot system is by far the most common with about 62% of the sprinkler (3.2 million) irrigated acres. Central pivot system has been transitioned from having sprinkler nozzles at the top of the pipe to mid-elevation and to low-energy spray sprinklers on the pivot. Such modifications has improved the application efficacy from 60% with traditional configuration to 85% by mid-elevation spray application (MESA) and up to 95-98% by low energy spray (or precision) application (LESA/LEPA). The energy use has also been reduced as the new configuration needs 25 psi at pivot point compared to 80 psi on traditional center pivots. The LESA/LEPA technique has little difference in application efficiency due to changing wind and weather over time and day-night differences. Decreased required run times due to better uniformity and improved application efficiency, and lower required application pressures combine to create large potential pumping energy savings. It also means that limited water resources can be stretched much further. However, because the same amount of water must be applied in less time due to the much smaller wetted radius, the very high application rate leads to justifiable concerns with ponding and/or runoff that must be managed. Therefore, in many areas such as the Pacific Northwest, it has been tried in limited ways without modifying practices to control runoff, and were subsequently abandoned as unworkable due to the observed higher runoff rates. In recent years (2014-2015) however, our team (Drs. Peters and Neibling) have modified the LEPA/LESA system and variants are being tested at cooperating grower sites for irrigating alfalfa, oats, wheat, corn, spearmint and grass seed production. One of the criticisms is that the real efficiency differences between LESA and MESA are overestimated since the water that is lost to wind drift and evaporation from MESA suppresses crop water use requirements downwind due to the resultant lower temperatures and increased humidity. To help quantify these differences it is important to measure canopy temperature differences on canopies of similar crops under both MESA and LESA. This data would help show where the additional energy is either lost or gained from evaporated water. Thus, proposed project is aimed at quantifying above phenomenon using the unmanned aerial system (UAS) based high resolution aerial infrared and multi-spectral images of the test fields where one span is LESA/LEPA and the remaining is MESA. Specifically, the project objectives are: 1) UAS based high resolution imaging of the LESA/LEPA vs MESA sights at two different times of the season to evaluate how the wetted canopy affects application efficiency, how it may suppress evapotranspiration demand, and to see differences in ponding and runoff, 2) Quantify water use efficiency (through canopy health) at various growth stages for row and field crops irrigated using modified LESA/LEPA systems, and 3) Map the high resolution remotely sensed field data and establish its relation to ground reference data including yield where possible. Ultimately, the project outcome will promote more efficient and effective use of water in agriculture. It will save water and energy in a way that benefits the farmer. High resolution images will also be useful to supplement physical demonstrations of the LEPA/LESA system and to assuage grower fears of the potential drawbacks of this technology. Leveraged will also be the funds from the Bonneville Power Administration, who are interested in the potential power savings. Getting preliminary data about the potential effects of evapotranspiration suppression should lead to an entirely new area of very important research that will likely be of great interest to state and federal funding agencies.