Impacts of Soil Moisture and Fertilizer on N[sub.2]O Emissions from Cornfield Soil in a Karst Watershed, SW China

Incubation experiments using a typical cornfield soil in the Wujiang River watershed, SW China, were conducted to examine the impacts of soil moisture and fertilizer on N[sub.2]O emissions and production mechanisms. According to the local fertilizer type, we added NH[sub.4]NO[sub.3] (N) and glucose (C) during incubation to simulate fertilizer application in the cornfield soil. The results showed that an increase in soil moisture and fertilizer significantly stimulated N[sub.2]O emissions in cornfield soil in the karst area, and it varied with soil moisture. The highest N[sub.2]O emission fluxes were observed in the treatment with nitrogen and carbon addition at 70% water-filled pore space (WFPS), reaching 6.6 mg kg[sup.−1] h[sup.−1], which was 22,310, 124.9, and 1.4 times higher than those at 5%, 40%, and 110% WFPS, respectively. The variations of nitrogen species indicated that the production of extremely high N[sub.2]O at 70% WFPS was dominated by nitrifier denitrification and denitrification, and N[sub.2]O was the primary form of soil nitrogen loss when soil moisture was >70% WFPS. This study provides a database for estimating N[sub.2]O emissions in cropland soil in the karst area, and further helped to promote proper soil nitrogen assessment and management of agricultural land of the karst watersheds.