Partial manure substitution in maize‐soybean intercropping reduces ammonia volatilization and increases yield and water‐use efficiency

Intercropping of cereals with legumes is a well‐established strategy for maximizing yield, but its effectiveness in water‐use efficiency (WUE) is not well recognized. This study aimed to investigate the effectiveness of manure and maize‐soybean intercropping on ammonia (NH 3 ) volatilization, yield, and WUE. A 2‐year field experiment was conducted using three cropping systems: maize monocrop ( Zea mays L.), soybean monocrop ( Glycine max L.), and maize‐soybean intercrop, along with four nitrogen (N) treatments: control, urea, manure, and partial replacement of urea with manure (manure + urea). Maize‐soybean intercropping reduced NH 3 volatilization by 29% and 18% compared to maize and soybean monocrops, respectively, with urea application being responsible for the highest emissions. Intercropped maize produced 43% more above‐ground biomass and 48% more grain yield than maize monoculture. The manure + urea treatment generally had the highest maize above‐ground biomass and grain yields. The dense canopy in intercropping reduced soil evaporation by 6% compared to maize and by 9% compared to soybean monocultures. Likewise, maize yield WUE in intercropping was 55% higher over 2 years compared to maize monoculture. The water equivalent ratio (relative water required in monocrop to produce the same yield in intercrop) ranged from 1.05 to 1.35, and the relative water‐saving index (intercrop water consumption compared to monocrop) ranged from −13.4% to −25.7%, indicating that intercropping consistently uses less water for the same yield compared to monocrops. Among N treatments, the highest WUE of maize yield was observed in the manure + urea treatment. Overall, combining maize‐soybean intercropping with partial urea substitution by manure is a promising agronomic practice for fostering a resilient and sustainable agroecosystem in semi‐arid regions.