Nitrous oxide emission and sweet potato yield in upland soil: Effects of different type and application rate of composted animal manures.

The aims of this study were to determine type and application rate of composted animal manure to optimize sweet potato yield relative to NO emissions from upland soils. To this end, the study was conducted on upland soils amended with different types and rates of composted animal manure and located at two geographically different regions of South Korea. Field trials were established at Miryang and Yesan in South Korea during the sweet potato (Ipomoea batatas) growing season over 2 years: 2017 (Year 1) and 2018 (Year 2). Three composted animal manures (chicken, cow, and pig) were applied at the rates of 0, 10, and 20 Mg ha to upland soils in both locations. In both Years and locations, manure type did not affected significantly cumulative NO emissions from soil during the sweet potato growing season or the belowground biomass of sweet potato. However, application rate of animal manures affected significantly the cumulative NO emission, nitrogen (N) in soil, and belowground biomass of sweet potato. An increase in cumulative NO emission with application rates of animal manures was related to total N and inorganic N concentration in soil. The belowground biomass yield of sweet potato but also the cumulative NO emission increased with increasing application rate of composted animal manures up to 7.6 and 16.0 Mg ha in Miryang and Yesan, respectively. To reduce NO emission from arable soil while increasing crop yield, composted animal manures should be applied at less than application rate that produce the maximum belowground biomass of sweet potato.