Ammonia emission characteristics and emission coefficients of wheat and corn rotation cropland under different fertilization methods in lime concretion black soil

Soil type affects farmland ammonia volatilization, but few studies have examined ammonia volatilization characteristics and emission coefficients. Therefore, the accurate inventory of regional farmland soil ammonia emissions is disadvantaged. Lime concretion black soil found in southern Henan, China, was used to explore the ammonia volatilization characteristics of winterwheat-summer maize-rotated cropland by the closed-sponge method. The soil was unfertilized (CK) or treated with traditional fertilizer (TR), optimized fertilizer (OPT), re-optimized fertilizer (ZOPT), or slow-controlled fertilizer (HK), and the ammonia emissions coefficient was determined. The results showed that the winter wheat and summer maize ammonia volatilization amounts using the traditional fertilizer treatment were 11.1 and 13.4 kg·hm^-2, respectively. Summer maize ammonia emission was 21% higher than winter wheat, indicating that the summer maize season was a high-volume period. Winter wheat and summer maize treated with HK and ZOPT had the lowest ammonia emission coefficients (HK:1.7% for winter wheat, 1.5% for summer maize; ZOPT:2.1% for winter wheat, 2.6% for summer maize; P < 0.05), the OPT treatment had moderate coefficients (2.6% for winter wheat, 3.6% for summer maize), and the TR treatment had the highest coefficients (3.6% for winter wheat, 4.7% for summer maize). The ammonia emissions fertilization gradients and fertilization amounts were plotted, and the ammonia volatilization amounts under variable fertilization treatments were linear (R²:0.931 for winter wheat, 0.934 for summer maize). These results may help to improve nitrogen fertilizer use and the ammonia emission inventory and provide basis for nitrogen emission estimation of winter wheat-summer maize rotation in lime concretion black soil croplands.