A combination of straw incorporation and polymer-coated urea offsets soil ammonia and nitrous oxide emissions in winter wheat fields

Abstract

The combined effects of straw incorporation (SI) and polymer-coated urea (PCU) application on soil ammonia (NH3) and nitrous oxide (N2O) emissions from agricultural fields have not been comprehensively evaluated in Northwest China. We conducted a two-year field experiment to assess the effects of combining SI with either uncoated urea (U) or PCU on soil NH3 emissions, N2O emissions, winter wheat yields, yield-scaled NH3 (INH3), and yield-scaled N2O (IN2O). Five treatments were investigated, no nitrogen (N) fertilizer (N0), U application at 150 kg N ha–1 with and without SI (SI+U and S0+U), and PCU application at 150 kg N ha–1 with and without SI (SI+PCU and S0+PCU). The results showed that the NH3 emissions increased by 20.98–34.35% following SI compared to straw removal, mainly due to increases in soil ammonium (NH4+-N) content and water-filled pore space (WFPS). SI resulted in higher N2O emissions than under the S0 scenario by 13.31–49.23% due to increases in soil inorganic N (SIN) contents, WFPS, and soil microbial biomass. In contrast, the PCU application reduced the SIN contents compared to the U application, reducing the NH3 and N2O emissions by 45.99–58.07 and 18.08–53.04%, respectively. Moreover, no significant positive effects of the SI or PCU applications on the winter wheat yield were observed. The lowest INH3 and IN2O values were observed under the S0+PCU and SI+PCU treatments. Our results suggest that single PCU applications and their combination with straw are the optimal agricultural strategies for mitigating gaseous N emissions and maintaining optimal winter wheat yields in Northwest China.