Effects of the Combining Straw Return with Urease Inhibitor on Ammonia Volatilization, Nitrogen Use Efficiency, and Rice Yield in Purple Soil Areas.

Straw return in rice ( Oryza sativa L.) paddy has been heavily criticized for its potential to influence ammonia (NH 3 ) volatilization loss due to irrational fertilizer N application. Therefore, improving the N fertilization strategies within residue straw systems is necessary to reduce N loss from NH 3 volatilization. This study investigated how the incorporation of oilseed rape straw and the urease inhibitor affected NH 3 volatilization, fertilizer N use efficiency (FNUE), and rice yields over two growing seasons (2018-2019) in the purple soil region. This study arranged eight treatments combined straw (2, 5, 8 ton ha -1 , named 2S, 5S, 8S, respectively), with urea or urease inhibitor (UI, 1% NBPT) with three replicates, which included control (CK), UR (Urea, 150 kg N ha -1 ), UR + 2S, UR + 5S, UR + 8S, UR + 2S + UI, UR + 5S + UI, UR + 8S + UI, based on the randomized complete block method. Our results indicated that incorporating oilseed rape straw increased NH 3 losses by 3.2-30.4% in 2018 and 4.3-17.6% in 2019 than the UR treatment, attributing to the higher NH 4 + -N content and pH value within floodwater. However, the UR + 2S + UI, UR + 5S + UI and UR + 8S + UI treatments reduced NH 3 losses by 3.8%, 30.3%, and 8.1% in 2018 and 19.9%, 39.5%, and 35.8% in 2019, separately compared to their corresponding UR plus straw treatments. According to the findings, adding 1% NBPT significantly decreased NH 3 losses while incorporating 5 ton ha -1 oilseed rape straw. Furthermore, adding straw, either alone or in conjunction with 1% NBPT, increased rice yield and FNUE by 0.6-18.8% and 0.6-18.8%, respectively. Otherwise, NH 3 losses scaled by yield in the UR + 5S + UI treatment decreased significantly between all treatments in 2018 and 2019. These results suggest that optimizing the oilseed rape straw rate combined with 1% NBPT applied with urea efficiently increased rice yield and reduced NH 3 emissions in the purple soil region of Sichuan Province, China.