Simulation of evapotranspiration of corn under mulched drip irrigation based on SIMDual_Kc model in Tongliao area of Inner Mongolia

Abstract: In recent years, the mulched drip irrigation due to its efficient irrigation has been promoted in Inner Mongolia. However, few studies have focused on this area. In this study, we investigated the difference soil evaporation under the film mulching and bare land in order to clarify the change law of evaporation of corn and explore the mechanism of water saving and yield increase of corn under mulched drip irrigation in Northeast of Inner Mongolia. The SIMDual_Kc model was used to simulate the change of crop coefficient. And the crop coefficient was used for soil evaporation calculation. The model was calibrated by the results from the filed experiment. The field experiment was carried out in 2014 and 2015. A total of 3 treatments including low, mid and high water treatments were designed based on field capacity. The corn was planted under the mulching and bare land. The soil moisture was determined by TDR and the soil evaporation was measured by standard and self-made lysimeters. Meanwhile, the corn height and leaf area were determined during the growing period of corn. The model calibration and validation results showed that the simulated soil moisture agreed well with the measured values. The R2 was 0.85-0.91 and the root mean square error was 1.0% and below. The soil moisture under the film mulching was lower than that of bare land after rainfall. It indicated that the film could prevent rainfall into soil. The simulated soil moisture of film mulching was higher than that of bare land, suggesting that the film could protect soil moisture from evaporation. Based on the simulation, the basal crop coefficient was 0.15, 1 and 0.4 under the bare land and 0.15, 1.05 and 0.4 under the film mulching in the early, middle and late growth stage of corn. In the early stage, the basal crop coefficient and its adjustment was similar for the treatment of bare land since the root was shallow and continuous rainfall. In the middle stage, the transpiration dominated and the soil evaporation coefficient was the lowest. In the later stage, the evaporation coefficient was slightly increased again. The change of basal crop coefficient and evaporation coefficient was similar for the film mulching and bare land treatments. The ratio of evaporation to crop evapotranspiration was calculated by using SIMDual_Kc model. The ratio of 2014 and 2015 were respectively 26.15%, 27.23% and 19.85%, 20.29% for bare land and film mulching. The ratio of film mulching was lower than that of bare land. The change amount of soil evaporation in bare land was 1.67-2.18 mm/d and that in film mulching was 1.33-2.17 mm/d. It showed that mulching can effectively reduce the soil evaporation, and has the potential to reduce crop water consumption. It can guide the production of corn under mulched drip irrigation in Northeast of Inner Mongolia.