Optimizing soil moisture-triggered automated irrigation and nitrogen management in wheat–maize systems using RZWQM2

Abstract

Climate change and water scarcity are major challenges to sustainable agriculture and crop productivity, especially with increasing global food demand around 70% by 2050. Excessive water and nitrogen use in agriculture accelerates environmental degradation and decreases crop water productivity (WPC) and net income. The aim of this work was to integrate of irrigation systems with different fertilization rates to optimize WPC, nitrogen efficiency, and to reduce deep percolation and nitrate leaching. Moreover, the efficiency of RZWQM2 to simulate soil water, yield, WPC, and evapotranspiration for long term about 38 years (1984–2021) was estimated under different scenarios. To estimate efficiency of RZWQM2 model, three treatments of irrigation and fertilization were SDIP=subsurface drip irrigation system with deficit irrigation and fertilization, FIL= Flood irrigation system with deficit fertilization, CK= recommended irrigation and fertilization, were carried out at Luancheng Agro-Ecosystem Experimental Station during 2023-2025. The results observed that RZWQM2 was accurately simulated soil moisture, crop growth, yield, biomass, and WPC (nRMSE: 9.02–29%), as well as leaf area index, evapotranspiration, plant and grain nitrogen uptake, deep percolation, and nitrogen leaching (R² up to 0.93). Long-term simulations identified optimal soil moisture–triggered irrigation strategies were 45% root-zone depletion threshold for wheat and 25% for maize with 80% recharge of plant-available water for both of them. We can conclude the interval between each irrigation for wheat is longer than maize as irrigation schedule under the same conditions. Overall, this study integrates lysimeter observations with long-term process-based modelling to demonstrate that moderate, crop-specific root-zone depletion offers a climate-resilient pathway for sustainable water and nitrogen management in wheat–maize system.