Evaluating Remote Sensing-based Crop Water Use Monitoring Methods Using Soil Moisture Sensors

Competition for limited water supplies continues to exert pressure on agriculture. In addition, climate change, urban growth, and drought influence how farmers manage their water supplies. Water transfers from agriculture to other uses are on the rise. To avoid drying farms one alternative water management strategy is to deficit irrigate. However, to perform a successful managing irrigation under a deficit irrigation regime an accurate crop water consumption monitoring method is required. The objective of this study was to evaluate a crop water stress model that is based on the difference between canopy radiometric temperature and air temperature. Three irrigation treatments were imposed on corn plots grown in northeastern Colorado in 2011. The treatments were: TrT 1 full irrigation (six irrigations), TrT 2 deficit irrigation (two irrigations), and TrT 3 reduced irrigation (six irrigation but half the amount of TrT 1). A local weather station located on a grass field was used to compute reference evapotranspiration. Derived crop water stress indices and water use amounts were evaluated with ET values derived from a Neutron probe-based soil water balance and with a surface energy balance model considering inputs from a remote sensing system. Results indicated that relatively low errors in ET estimation are possible if surface radiometric temperature is acquired earlier in the day.