Effects of the combination of straw incorporation and urease inhibitor on ammonia volatilization, nitrogen use efficiency, and grain yield in southwestern China

Abstract The maintenance of crop residues is essential for sustainable soil management, enhancing the ammonia (NH3) volatilization loss due to fertilizer-N. Therefore, implementing the N fertilization strategies within residue straw systems is necessary to reduce N loss. This work investigated how oilseed rape straw incorporation and urease inhibitor applied with urea affected NH3 emissions, N use efficiency (NUE), and rice yields within two growing seasons. This work arranged eight treatments having three replicates, which included urea (UR), urea + 2 Mg ha− straw (UR + 2S), urea + 5 Mg ha− straw (UR + 5S), urea + 8 Mg ha− straw (UR + 8S), urea + 2 Mg ha− straw + 1% NBPT (UR + 2S + UI), urea + 5 Mg ha− straw + 1% NBPT (UR + 5S + UI), urea + 8 Mg ha− straw + 1% NBPT (UR + 8S + UI) and non-urea fertilizer (control), based on the randomized complete block method. Our results indicated that incorporating oilseed rape straw increased NH3 losses by 3.22%-21.51% in 2018 and 30.18%-51.43% in 2019 than the UR treatment, attributing to the higher NH4+-N content and pH value within floodwater. The UR + 2S + UI and UR + 8S + UI enhanced NH3 losses by 2.70%-24.00% in 2019, relative to the oilseed rape straw addition alone. However, combined application of 5 Mg ha− straw and 1% NBPT (UR + 5S + UI) reduced NH3 losses by 26.20% in 2018 and 14.60% in 2019, separately (P < 0.05) when compared with 5 Mg ha− oilseed rape straw only (UR + 5S). Based on the results, adding 1%, NBPT significantly decreased NH3 losses while 5 Mg ha− oilseed rape straw incorporation was applied. Moreover, adding straw alone or in combination with NBPT elevated rice yield by 0.78%-21.21% and NUE from 13.13–21.72%. Otherwise, yield-scaled NH3 emissions within the UR + 5S + UI treatment significantly decreased among all the treatments in 2018 and 2019. Our results indicated that optimizing the oilseed rape straw rate combined with 1% NBPT applied with urea efficiently increased rice yield and reduced NH3 emissions in southwestern China.