Quantifying soil N 2 O emissions from soil and anaerobically digested swine manure, nitrification and denitrification using 15 N isotope labeling method

Increasing use of anaerobically digested swine manure in the farmland makes it necessary to understand its impact on N 2 O emissions, regarding the source of N 2 O and the corresponding mechanism of action. We used a 15 N-labeled sulfate modifying the soil in order to identify the sources of N 2 O and the pathways of nitrification and denitrification. Three soil moisture contents (50% WHC, 75% WHC, and 100% WHC) along with three levels of anaerobically digested swine manure (0 g·kg −1 , 10 g·kg −1 , and 25 g·kg −1 ) were tested using randomized block design. Although the combined effect of contents of anaerobically digested swine manure and the soil moisture contents added to the system stimulated the utilization of soil N and promoted denitrification, the process of nitrification dominated. In anaerobically digested swine manure-treated soils, the rate of contribution of anaerobically digested swine manure to N 2 O accounted for 68.6–99.8%. In the 25 g·kg −1 treatment, the maximum of N 2 O produced by denitrification and nitrification were 14.1% and 93.1%.