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).
