Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2013
Publication Date: 1/9/2014
Citation: O'Shaughnessy, S.A., Evett, S.R., Colaizzi, P.D., Howell, T.A. 2014. Wireless sensor network effectively controls center pivot irrigation of sorghum. Applied Engineering in Agriculture. 29(6):853-864.
Interpretive Summary: Many producers in the Great Plains region operate multiple center pivot systems. Automating irrigation scheduling by remotely sensing crop water stress can improve irrigation and time management. Automated irrigation scheduling has been a subject of research work at the Conservation and Production Research Laboratory at Bushland, Texas since the 1990’s. In these previous research studies, crop monitoring and automatic irrigation scheduling had been accomplished with wired sensors, multiplexers, and data loggers. Although wired systems are highly reliable, they are not practical for large scale agricultural applications. Their limitations include a restricted area of coverage, inflexibility in changing the network layout, relatively high capital costs, and involve maintenance of the cabling and intermediate data logging units. In this study, a wireless sensor network comprised of infrared thermometers, multiband radiometers, and a global positioning sensor (GPS) unit were used to monitor crop water stress, schedule irrigations, and control a six-span center pivot system. While there were intermittent issues with data dropout from the wireless sensors, treatment plots that were irrigated with automatic methods produced grain yields and water use efficiency that was similar to those produced from manual methods of irrigation scheduling using direct soil water measurements. These results indicate that it is possible to control automatic irrigation scheduling with a wireless sensor network system on a large-sized pivot field.
Technical 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 equipped 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 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.