Development of mechanistic models for nitrous oxide emissions from two soil types amended with manure composts at different ammonium nitrogen rates

Abstract

Existing process-based biogeochemical models do not sufficiently assess the impacts of manure composts on nitrous oxide (N2O) emissions due to a lack of model equations satisfactorily explaining N2O emission mechanisms in manure compost-amended soils. We aimed to develop mechanistic models for N2O emissions in nitrification and denitrification processes from two soil types amended with two manure compost types at different initial ammonium N (NH4+ -N) rates. The data of N2O emissions and NH4+-N and Nitrate N (NO3- -N) contents from an aerobic incubation experiment, which used cattle manure compost and mixed compost-amended Kochi (K) and Ushimado (U) soils at three different initial NH4 + -N rates were used for model development. The linear models for N2O emissions were developed using parameters of soil NH4 + -N (nitrification) or NO3 - -N (denitrification) contents. In addition, N2O emissions in nitrification showed a steady state with consumed NH4 + -N contents. In the linear model, NH4 + -N contents could satisfactorily evaluate N2O emissions in nitrification in both manure compost-amended K and U soils regardless of the initial NH4 + -N rates. The regression coefficient value of the linear model clearly showed the effects of soil and compost properties on N2O emissions. In the model for N2O emissions in denitrification, NO3 - -N contents reasonably reflected N2O emissions only in K soil. In conclusion, N2O emissions in manure compost-amended soils can be assessed by NH4 + -N (both K and U soils) and NO3 -N contents (only K soil).