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

The combined effects of straw incorporation (SI) and polymer -coated urea (PCU) application on soil ammonia (NH 3 ) and nitrous oxide (N 2 O) 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 NH 3 emissions, N 2 O emissions, winter wheat yields, yield -scaled NH 3 ( I NH3 ), and yield -scaled N 2 O ( I N2O ). Five treatments were investigated, no nitrogen (N) fertilizer (N 0 ), U application at 150 kg N ha -1 with and without SI (SI+U and S 0 +U), and PCU application at 150 kg N ha -1 with and without SI (SI+PCU and S 0 +PCU). The results showed that the NH 3 emissions increased by 20.98-34.35% following SI compared to straw removal, mainly due to increases in soil ammonium (NH 4 + -N) content and water -filled pore space (WFPS). SI resulted in higher N 2 O emissions than under the S 0 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 NH 3 and N 2 O 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 I NH 3 and I N2O values were observed under the S 0 +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.