Decision support system and weather forecast data for modeling open field vegetable crops evapotranspiration

Usually, irrigation scheduling is based on a soil water balance approach that considers reference evapotranspiration and crop coefficients as inputs. However, these crop coefficients come from the literature and the whole approach does not take into account field variability in canopy vigour, among other factors. The current study compared a novel irrigation model (Riego-Asesor, RA), which determines soil evaporation and plant transpiration separately using crop characteristics and weather forecasts as inputs, with the standard irrigation farmer practices (F). Such comparison was performed on four open field vegetation seasons, two in endive and one in muskmelon, in south-eastern Spain. The irrigation volume applied, crop aboveground biomass, water content, relative chlorophyll content (SPAD) and yield were determined in both treatments. Water savings around 8% for RA when compared with the F treatment have been observed. Farmer’s watering regime was already well adjusted to the crop water needs and this, combined with the leaching fraction applied due to the high salinity levels of the irrigation water employed in the area, impeded to attain greater water savings. In sight of the results obtained from the field experiments, it can be concluded that the proposed model is able to mimic successfully the irrigation management performed by the farmer without the use of on-the-ground sensors. The main discrepancies observed between the two approaches were caused by the fact that the Riego-Asesor model does not consider special management practices during specific moments of the growing season. Nevertheless, when no specific actions were adopted by the farmer, Riego-Asesor tended to estimate lower irrigation volumes, resulting in water savings.