Nitrogen fertilizer reduction in combination with<i>Azolla</i>cover for reducing ammonia volatilization and improving nitrogen use efficiency of rice

Abstract

RN₁₅A and RN₃₀A substantially reduced total AV by 50.3 and 66.9% compared with FN, respectively, primarily due to the lower surface water ammonia concentrations and pH. RN improved the efficiency of <i>Azolla</i> cover on reducing AV, with 4.1-9.9% higher than for FN. Compared with the FN, RN₁₅A and RN₃₀A enhanced apparent N recovery efficiency (ANRE) by 46.5 and 39.1%, which might be responsible for the lower NH₃ emission and the increased total N uptake / total chemical N applied. Furthermore, RN₁₅A and RN₃₀A reduced yield-scaled volatilization by 52.3 and 64.3% than for FN, respectively. Thus, combining 15-30% RN with <i>Azolla</i> cover may be a way to reduce AV and improve ANRE without decreasing rice grain yield.