Simulation of maize crop behavior under deficit irrigation using MOPECO model in a semi-arid environment

Through the experimental data of a three year maize field test, this paper shows the calibration (year 2003) and validation (years 2001 and 2002) processes for the simulation of FAO-700 maize crop (Dracma and Brasco hybrids) under deficit irrigation conditions in Castilla-La Mancha (Spain) using the MOPECO model. Key objectives of this research were: (1) determining the length of growth stages using the growing-degree-days (GDD) method; (2) an analysis of the effect of saline irrigation water on crop yield; and (3) a sensitivity analysis of the main factors affecting gross margin (i.e. irrigation water cost, harvest sale price, and uniformity of irrigation). Results show that MOPECO is suitable for simulating the yield versus total water (gross irrigation + effective rainfall) relationships under the climatic and soil conditions in this study (RMSE = 1199 kg ha−1, relative error = 7.7%, and similarity rate = 0.94, between observed and simulated yields). GDD for the whole growth cycle is around 1802.8 °C, while calibrated crop coefficient (Kc) and crop yield response (ky) values for the four growth stages proposed by FAO-56 are similar to those presented in the literature, which provides evidence that this methodology is appropriate for simulating the behavior of herbaceous crops such as maize under different scenarios of water supply. The electrical conductivity of the irrigation water in the area (0.85 dS m−1) does not significantly affect the final yield of this crop (up to 4.7% higher without considering the effect of salinity) for the irrigation amount commonly applied in the area (around 650 mm). Under the current harvest sale price scenario (0.15€ kg−1), costs have greatly decreased the profitability of maize in the area, reaching 400€ ha−1. Changing the management of the crop for deficit irrigation strategies may save water that can be used by other crops, thereby obtaining a higher gross margin on farms.