Performance of a Wireless Sensor Network for Crop Water Monitoring and Irrigation Control

Abstract

Robust automatic irrigation scheduling has been demonstrated using wired sensors and sensor network systems with subsurface drip and moving irrigation systems. However, there are limited studies that report on crop yield and water use efficiency resulting from the use of wireless networks to automatically schedule and control irrigations. In this study, a multinode wireless sensor network (WSN) system was mounted onto a six-span center pivot outfitted with a commercial variable rate irrigation (VRI) system. Data from the WSN was used for automatic irrigation scheduling and irrigation control to produce an early hybrid variety of grain sorghum in 2011. An integrated crop water stress index (CWSI) was used as a threshold to schedule irrigations. Half of the center pivot field was divided into six sectors, three were irrigated using automatic control, and three were irrigated based on weekly direct soil water measurements. Wireless sensor nodes, i.e. infrared thermometers, GPS unit, and multiband radiometers were integrated onto the center pivot system and field below. The WSN system was scaled to 40 different nodes and was operational throughout 98% of the growing season. An assessment of the reliability of the nodes, demonstrated that delivery rates for data packets from the different nodes ranged between 90% to 98%. Automatic irrigation scheduling succeeded in producing mean dry grain yields and controlling crop water use efficiency (WUE) at levels that were similar to those from soil water based irrigation scheduling. Average seasonal integrated crop water stress indices were negatively correlated to irrigation treatment amounts in both the manual and automatic plots and correlated well to crop water use. These results demonstrate that it is feasible to use WSN systems for irrigation management on a field scale level.