Context: The contradiction between high agricultural yields and water resource shortages is becoming increasingly serious. Reducing nitrogen appropriately with green manure retention can ensure high agricultural yields,  but it remains unclear whether it can optimize crop water consumption characteristics and improve water  productivity (WPc).  

Objective: This study aims to investigate the effect of green manure retention combined with nitrogen reduction  on water use characteristics of maize and its potential mechanisms.  

Methods: A field experiment was conducted at Wuwei Oasis Agricultural Experimental Station in China from  2020 to 2022, with five treatments: (i) traditional nitrogen application with green manure retention (N100), (ii)  nitrogen reduction by 10 % with green manure retention (N90), (iii) nitrogen reduction by 20 % with green  manure retention (N80), (iv) nitrogen reduction by 30 % with green manure retention (N70), and (v) nitrogen  reduction by 40 % with green manure retention (N60).  

Results: The results showed that compared with the N100 treatment, 0-50 cm maize root biomass (RB), biomass  accumulation (BA), and canopy cover (CC) were not significantly reduced in the N80 treatment. This model  ensured a stable grain yield (GY) and improved 0− 50 cm soil water storage (SWS) by 7.1− 13.1 %. It effectively  suppressed soil evaporation (E), promoted maize transpiration (T), reduced maize evapotranspiration (ET) by  4.8 %, and increased WPc by 1.8− 26.6 %. Structural equation modeling (SEM) suggests that RB was the most  important factor for improving WPc. In addition, this system ensures that economic benefits did not decrease.  

Conclusion: It can be seen that nitrogen reduction by 20 % with green manure retention is a reasonable nitrogen  fertilizer management system to alleviate the contradiction between high maize yield and water resource  shortages in the region.  

Implications: The results of this study provide valuable insights into alleviating the contradiction between agricultural production and regional water resource scarcity.