Irrigatmo: no-moving parts system for feed-back and feed-forward irrigation scheduling

The weather-based approach quantifies the crop water requirements (CWR) using a simplified agrohydrological model coupled with meteorological sensors. FAO56 (Allen et al., 1998) is one of the most used bucket models for CWR. In this model, the daily ET0 is usually estimated by the FAO-Penman-Monteith (PM), which needs as inputs standard atmosphere forcings acquired from weather stations that often are equipped with ordinary mechatronics sensors that require regular maintenance. An atmometer (ETgage) is an accurate sensor with no moving parts that continuously measures the ET0 based on a physical analogy of the crop reference. This study aims to design and validate an expert system, named Irrigatmo, to manage irrigation based on the combined application of the feedforward- (FFc) and feedback- (FBc) control irrigation scheduling protocols. The FFc protocol comprises a Kc-based mass balance model instructed with a modified atmometer and FDR sensors for sub-hourly ET0 and soil water content (SWC) measurements. At the same time, the FBc protocol uses the SWC to quantify the critical condition and the crop stress coefficient to adjust the Kc value used in the bucket model. The ETgage was modified by integrating a pressure transducer sensor, calibrated to continuously measure the water level and, therefore, estimate ET0 at a sub-hourly scale. The results showed that Irrigatmo detected accurately and rapidly the changes in atmospheric and soil water conditions. Based on these fine-detected dynamics, the system decided to turn on/off the irrigation valve according to the set irrigation thresholds. In this way, Irrigatmo is a promising tool to adjust precisely and automatically irrigation variables.