Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/14/2015
Publication Date: 9/17/2015
Citation: Colaizzi, P.D., Oshaughnessy, S.A., Evett, S.R. 2015. Center pivot mounted infrared sensors: Retrieval of ET and interface with satellite systems [abstract]. Internatinal Workshop on Evapotranspiration Mapping for Water Security, September 15-17, 2015, Washington, D.C.
Technical Abstract: Infrared sensors mounted aboard cener pivot irrigation systems can remotely sense the surface temperatures of the crops and soils, which provides important information on crop water status. This can be used for irrigation management and irrigation automation, which can increase crop water productivity, reduce energy consumed, and reduce irrigation management time required of producers. Scientists at the USDA-ARS Soil and Water Management Research Unit, Bushland, Texas developed wireless infrared sensors and a wireless mesh network designed for center pivots, and made several important advances to a two-source energy balance model used to calculate evaporation (E), transpiration (T), and evapotranspiration (ET), and detect crop water stress. The combined use of the wireless sensors and the two-source energy balance model were tested and compared to independent calculation of ET derived from a soil water balance, where the change in the soil water profile was measured weekly to monthly by a field-calibrated neutron probe during a cotton season in 2013 at Bushland, Texas, USA. Descrepancies between ET calculated by infrared sensors and the two-source model and ET derived from the soil water balance (neutron probe measurements) included RMSE and MBE of 12.5 mm (31%) and -2.6 mm (-6.5%), respectively, where numbers in parentheses were relative to the mean ET derived from the soil water balance. These descrepancies were larger than a similar study where ET was measured by large weighing lysimeters and using stationary infrared sensors. The larger descrepancies in the present study may have resulted from greater uncertainties in soil water balance closure, plant width, height, and leaf area index, sensor soil-vegetation view factors, and relatively infrequent (weekly to monthly) soil water measurements. This approach nonetheless provided a feasible and cost-effective method to map ET within a center pivot field at spatial resolutions (< 10 m) and repeat frequencies (3 to 5 d) similar to or better than satellite systems. Future studies will include more frequent soil water measurements using a new waveguide-on-access-tube (WOAT) sensor, and separate measurements of E and T.