Optimum sensor location for irrigation scheduling of cotton in a field with variable soil

Fields in the southeastern coastal plain region have a high degree of variability in soil type and topography, with some areas of the field wetter or dryer than other areas. Efficient irrigation in these fields is best achieved using a sensors-based variable rate irrigation (VRI) system, which takes all of these variations into consideration. However, where the moisture sensors are located in a field can significantly affect irrigation scheduling decisions. Replicated tests were conducted during 2012 and 2013 growing seasons to determine the most accurate and affordable sensor technology for irrigation scheduling in cotton production and to determine the optimum sensor location in a production field with soil variations. The tests involved four commercially available moisture sensors. The results suggested that, in a production field with soil variability, it would be beneficial to install moisture sensors in management zones with higher EC readings (heavier soil textures) to obtain maximum yield and WUE. However, this may not be true during a dry year, since the 2012 and 2013 growing seasons had above 500 mm of precipitation compared to average rainfall of 280 mm. The results also showed that decagon sensor offered more promise for irrigation scheduling than the rest of the sensors tested, since it offered good accuracy and is affordable.