Peer Review #2 of "Effects of fertilizer and biochar applications on the relationship among soil moisture, temperature, and N2O emissions in farmland (v0.1)"

Background.Di-nitrogen oxide (N 2 O) emissions from soil may lead to nonpoint-source pollution in farmland.Improving the C and N content in the soil is an excellent strategy to reduce N 2 O emission and mitigate soil N loss.However, this method lacks a unified mathematical index or standard to evaluate its effect.Methods.To quantify the impact of soil improvement (C and N) on N 2 O emissions, we conducted a 2-year field experiment using biochar as carbon source and fertilizer as nitrogen source, setting three treatments (fertilization (300 kg N ha -1), fertilization + biochar (30 t ha -1), control).Results.Results indicate that after biochar application, the average soil water content above 20 cm increased by ~26% and 26.92% in 2019, and ~10 % and 12.49 % in 2020.The average soil temperature above 20 cm also increased by ~2% and 3.41% in 2019.Fertigation significantly promotes the soil N2O emissions, and biochar application indeed inhibited the cumulation by approximately 52.4% in 2019 and 33.9% in 2020, respectively.N 2 O emissions strongly depend on the deep soil moisture and temperature (20-80 cm), in addition to the surface soil moisture and temperature (0-20 cm).Therefore, we established an exponential model between the soil moisture and N 2 O emissions based on theoretical analysis.We find that the N 2 O emissions exponentially increase with increasing soil moisture regardless of fertilization or biochar application .Furthermore, the coefficient a < 0 means that N 2 O emissions initially increase and then decrease.The a RU < a CK indicates that fertilization does promote the rate of N 2 O emissions.And the a BRU > a RU indicates that biochar application mitigates this rate induced by fertilization.This conclusion can be verified by the sensitivity coefficient (SC B of 1.02 and 14.74; SC U of 19.18 and 20.83).Thus, we believe the model can quantify the impact of soil C and N changes on N 2 O emissions.We can conclude that biochar does significantly reduce N 2 O