Effects of N Reduction and Combined with Organic Fertilizer Application on Rice Yield and NH3 Volatilization from Saline Soil

Organic fertilizer (OF) application can significantly enhance soil fertility and crop yield. However, its influence on nitrogen (N) loss via ammonia (NH3) volatilization from reclaimed coastal paddy soil is not well known. We conducted a pot experiment here using cyanobacteria compost of sawdust and chicken manure plus cyanobacterial sludge, with four treatments, i.e., no urea-N (CK), urea-N (U), 80% urea-N (RU), and 80% urea-N plus compost (RU+OF), to examine these effects. The results showed that reducing urea-N input increased rice grain yield by 29.9–52.1% compared to U treatment. However, RU+OF produced significantly lower rice grain than RU by 14.6%. More straw biomass and N uptake did not translate into higher rice grain yield under OF-amended treatment. Interestingly, compared to the other treatments, RU+OF significantly mitigated NH3 volatilization by 8.9–25.3%, achieving the lowest emissions and the greatest reduction. A 20% reduction in N application rate combined with compost enhanced crop apparent N recovery efficiency and lowered NH3 volatilization. Therefore, organic substitution through combined compost application has potential as a component of reduced-N fertilization strategies in reclaimed coastal paddy soil.