Automatic Irrigation Control System for Soilless Culture Based on Feedback from Drainage Hydrograph

In a soilless culture, water and nutrients must be frequently and precisely applied due to the reduced volume and low water holding capacity of the substrate. We describe a low-cost and efficient control system for the irrigation management of soilless culture based on an irrigation tray. Both irrigation and drainage volumes from the irrigation control tray are measured automatically. The proposed irrigation scheduling options were based on applying both variable timing and amounts. A Proportional Integral Derivative (PID) algorithm was used to establish the irrigation timing option while two different irrigation application options, based on measurements from the drainage hydrograph, were developed and tested. A field test performed on a tomato crop was carried out to assess the performance of the two irrigation application options. Both irrigation algorithms performed well as they fitted the leaching fraction for every irrigation event to the target value. The fruit yield and quality were comparable to results obtained from the control treatment of the tomato crop. The designed low-cost irrigation control system, if implemented on commercial farms, could prove to be economically very beneficial. Keywords: Automation, Drainage hydrograph, Irrigation control tray, Irrigation scheduling, Proportional-Integral-Derivative (PID) controller, Substrate culture.