Nitrous oxide emissions from a rainfed-cultivated black soil in Northeast China: effect of fertilization and maize crop

Abstract

Nitrous oxide emission (N2O) from applied fertilizer across the different agricultural landscapes especially those of rainfed area is extremely variable (both spatially and temporally), thus posing the greatest challenge to researchers, modelers, and policy makers to accurately predict N2O emissions. Nitrous oxide emissions from a rainfed, maize-planted, black soil (Udic Mollisols) were monitored in the Harbin State Key Agroecological Experimental Station (Harbin, Heilongjiang Province, China). The four treatments were: a bare soil amended with no N (C0) or with 225 kg N ha−1 (CN), and maize (Zea mays L.)-planted soils fertilized with no N (P0) or with 225 kg N ha−1 (PN). Nitrous oxide emissions significantly (P < 0.05) increased from 141 ± 5 g N2O-N ha−1 (C0) to 570 ± 33 g N2O-N ha−1 (CN) in unplanted soil, and from 209 ± 29 g N2O-N ha−1 (P0) to 884 ± 45 g N2O-N ha−1 (PN) in planted soil. Approximately 75 % of N2O emissions were from fertilizer N applied and the emission factor (EF) of applied fertilizer N as N2O in unplanted and planted soils was 0.19 and 0.30 %, respectively. The presence of maize crop significantly (P < 0.05) increased the N2O emission by 55 % in the N-fertilized soil but not in the N-unfertilized soil. There was a significant (P < 0.05) interaction effect of fertilization × maize on N2O emissions. Nitrous oxide fluxes were significantly affected by soil moisture and soil temperature (P < 0.05), with the temperature sensitivity of 1.73–2.24, which together explained 62–76 % of seasonal variation in N2O fluxes. Our results demonstrated that N2O emissions from rainfed arable black soils in Northeast China primarily depended on the application of fertilizer N; however, the EF of fertilizer N as N2O was low, probably due to low precipitation and soil moisture.