Using sensor-based control to optimize soil moisture availability and minimize leaching in commercial strawberry production in Spain
The major strawberry production area in Spain is centered in Huelva province (SW Spain), with over 7,500 ha cultivated with drip fertigation under plasticulture production. Research in 2015 greatly increased drip irrigation efficiency by pulsing short (15-20 min) irrigation events during the day, increasing yields by more than 20 g plant-1, with an increased income of 1,300 ha-1. In 2016, we implemented an automated sensor-based control technology (Mayim, LLC; Pittsburgh, USA) to see if we could improve on these gains in efficiency. A sensor network was installed in November 2015 in two production tunnels, one to monitor the pulse irrigation events made by the grower, the other to implement sensor-based irrigation control. Soil moisture was monitored in each tunnel with three radio enabled data loggers (Em50R and nR5-DC, Meter-Group, Inc., Pullman, USA), each with 10HS soil moisture sensors (Meter-Group, Inc.) at 10 and 20 cm depths in the root zone. Sensor-controlled irrigation was initiated when the average soil volumetric water content (VWC) decreased below a set-point of 19%, which optimized VWC throughout the 35 cm bed depth. The nR5-DC node controlled irrigation events by opening and closing a l2V-DC latching solenoid (Netafim) via a relay on the node. Water applications in each tunnel were also monitored in real-time with flow meters (Zenner International GmbH & Co. KG, Saarbrücken, Germany). Additionally, soil matric potential (at 10 cm in the root zone) and electrical conductivity (EC) (at 35 cm for nutrient leaching) were monitored using MPS-6 and GS3 sensors (Meter-Group, Inc.), respectively. All sensor data were logged and transmitted to a computer and base station on the farm, which was connected to the internet via an air-card modem. All data were downloaded into a sophisticated graphical database program (SensorwebTM, Mayim, LLC), which also allowed real-time communication with the control nodes to adjust irrigation events, if needed. The SensorwebTM software provides micro-pulse (1-5 min) irrigation control capabilities, which further optimises irrigation water applications. During the 15 weeks of the study (January 27-May 11, 2016), pulse-irrigation applied 7,618 m3 ha-1 of irrigation water in 2-5 pulses day-1, compared to 3,141 m3 ha-1 applied with sensor-based control (58.8% less water). Estimated crop water use (ETc) for this period was 2,954 m3 ha-1. Sensor-controlled irrigation applied 110% of ETc vs. 261% for the pulse irrigation treatment during this period. During this time, root zone matric potential averaged less than -10 kPa in both treatments, with minimal leaching of salts below 35 cm for sensor-controlled irrigation.
Guéry, S., Lea-Cox, J.D., Martinez Bastida, M.A., Belayneh, B.E. and Ferrer-Alegre, F. (2018). Using sensor-based control to optimize soil moisture availability and minimize leaching in commercial strawberry production in Spain. Acta Hortic. 1197, 171-178
plasticulture, sensor-controlled irrigation, volumetric water content, water potential