Simulating the effects of irrigation and tillage on soil water, evapotranspiration, and yield of winter wheat with RZWQM2

Agricultural water shortages threaten food security worldwide, particularly in the North China Plain (NCP) which is an important grain production base in China. To solve this problem, we studied the effects of two tillage methods (no tillage: NT and plow tillage to 15 cm: PT) combined with two different irrigation timing (I1, 60 mm at the jointing stage and I2, 60 mm at 10 days after the jointing stage) on the grain yield of winter wheat and crop water productivity (CWP). The experimental results were used to calibrate the RZWQM2 model to improve its application in the NCP. The simulation results of the model could be used to compensate for the shortcomings of field experiments. The RZWQM2 model was calibrated and validated using the winter wheat growth data from 2015 to 2019. The normalized root mean square error (calibration and validation) between simulated and measured soil water storage (SWS), evapotranspiration (ET), leaf area index (LAI), biomass, and grain yield was 8.43 %-11.99 %, 4.39 %-8.67 %, 13.71 %-19.87 %, 16.37 %-19.36 %, and 13.83 %-17.71 %, respectively. NT improved the measured soil moisture status but decreased measured yield. However, I2 compensated for the negative effect of NT and resulted in a higher measured CWP than that after I1. The modified RZWQM2 model was used to calculate the actual transpiration and actual evaporation (AE) to expand the experimental results and reveal the effect of different treatments on actual evapotranspiration (AET). NT reduced the simulated AE during the entire growth period, reducing AET and increasing CWP. However, compared with the simulation effect of SWS and ET, the simulation effect of LAI, biomass, and grain yield was worse, and it was evident that improvements to the plant growth model are required. This study demonstrated that NT combined with delayed irrigation (10 days after the jointing stage) can improve soil moisture status and increase CWP in the NCP.

Automated summary

This study demonstrates that no-tillage combined with delayed irrigation (10 days after the jointing stage) can improve soil moisture status and increase crop water productivity in the North China Plain.