Modelling the effects of conservation tillage on crop water productivity, soil water dynamics and evapotranspiration of a maize-winter wheat-soybean rotation system on the Loess Plateau of China using APSIM

Information relating to the accurate quantification of the impacts of long-term conservation tillage practices on the crop yields and water use patterns of rainfed rotational cropping systems under global climate change is urgently required. The objectives of this study were to calibrate and evaluate APSIM (Agriculture Production System sIMulator) to accurately predict crop growth and development of a maize-winter wheat-soybean rotation, and to investigate the effects of conservation tillage on grain yield, water productivity and evapotranspiration on the Loess Plateau of China. This study integrated APSIM-based simulation modelling and field-level data collected from a maize-winter wheat-soybean rotation system under conventional tillage (CT) and no tillage with stubble retention of the previous crop (NTR) in Xifeng, Gansu, China. APSIM was successfully calibrated and evaluated using the root mean square error (RMSE) and index of agreement (d), indicating good performance on simulating the crop yield, dry matter biomass and soil water dynamic of the three crops for both CT and NTR treatments. Under the long-term scenario simulations (50 a, 25 rotation phases in total), the results showed that NTR improved soil water storage by 0–159 mm (72 mm on average; P < 0.01) of soil water storage before each rotation phase. The grain yield and biomass of winter wheat were significantly improved under the NTR treatment (1805 and 4309 kg ha⁻¹ on average), but changes in maize or soybean were not significant (P > 0.05). On a system basis, the NTR treatment had significantly greater plant transpiration (Tc) and Tc/system water supply (WSₛyₛ), but lower soil evaporation (Eₛ), evapotranspiration (ET), and ET/WSₛyₛ than treatment CT did. Additionally, Tc and Eₛ for maize production were not significantly different between the two treatments. Grain yield water productivity (WPY) and biomass water productivity (WPB) in wheat and soybean were substantially improved by 1.9–8.0 kg ha⁻¹ mm⁻¹ (P < 0.05) under treatment NTR. In general, we advocated that conservation tillage has indicated great potential for improving crop/water productivity and soil water storage under rainfed conditions in the semiarid Loess Plateau region of China.