Simulation of soil moisture dynamics, evapotranspiration, and water drainage of summer maize in response to different depths of subsoiling with RZWQM2

The contraindications of summer maize production, water resource shortages, and soil surface layer structural deterioration in the North China Plain (NCP) have become increasingly prominent. Subsoiling has been widely studied as a key tillage conservation technique. The objective of this experiment is to continue characterization of soil moisture dynamics, soil water consumption and drainage under different tillage management. In the present study, two subsoiling depths—35 cm (S35 + R15) and 40 cm (S40 + R15)—were examined and rotary tillage at 15 cm (R15) was used as the control. The volume moisture content of field soil was determined by Time Domain Reflectometry. The amount of water stored in the soil is calculated by the soil volumetric moisture content in the 0–130 cm soil profile cumulated. The amount of water stored in the soil at sowing and harvest time was used to calculate ET using the equation of water balance. The field experiment results were combined with the Root Zone Water Quality Model (RZWQM2) to calibrate and verify RZWQM2 using experimental data for summer maize in the growth period from 2017 to 2019. The results of the field trials showed that the soil water content (SWC) and evapotranspiration (ET) were increased by subsoiling compared to that by R15. RZWQM2 showed promising applicability in this scenario and successfully simulated the soil water dynamics caused by rainfall distribution during the years of treatment by R15, S35 + R15, and S40 + R15. The normalized root mean squared errors (nRMSE) for soil water storage (SWS) and ET were 11.31–19.65% and 11.99–16.57%, respectively. The corrected model was used to supplement the calculations of actual transpiration (AT), actual evaporation (AE), and water drainage. According to the calculations of the model, S35 + R15 and S40 + R15 treatments could effectively reduce the actual evaporation in the early growth period and maintain high transpiration in the middle and late growth periods. However, S40 + R15 treatment also resulted in a higher water drainage rate and greater cumulative water drainage. In terms of soil moisture dynamics, our findings suggest 35 cm to be the optimal depth for subsoiling in the NCP. Concurrently, the results suggest that increasing the depth of the subsoiling may lead to more water drainage.