Combining straw amendment and nitrification inhibitor to mitigate soil N losses during cooling-warming and freeze-thaw cycles

Post-harvest losses of nitrogen (N) from agricultural fields causes environmental damage due to N leaching and greenhouse gas emissions. Two potential strategies to mitigate these losses are amending soil with straw and applying nitrification inhibitors (NIs). Combining these strategies could have a synergistic effect, reducing nitrification and promoting the long-term microbial N immobilization. However, the effect of seasonal temperature fluctuations on N losses – when straw and NIs are applied together – is poorly understood. To investigate this, we conducted a 3-month mesocosm experiment examining the impact of wheat straw amendment and NI on soil N losses via N$_2$O emissions and leaching, depending on temperature variation (freezing-thawing vs cooling-warming), with and without mineral N fertilization. We observed an increase in N$_2$O emissions immediately after applying the straw and N fertilizer, which was reduced by 58% with NI application. Both freezing-thawing and mild cooling-warming led to increase in net N mineralization, causing a second N$_2$O emission peak. However, adding straw reduced N leaching by 70%, thus mitigating total N losses. ... mehrThe positive overall effect of the combined application of straw and NI resulted from the selective actions of each measure: the N immobilization induced by straw reduced leaching, while NI application decreased N$_2$O emissions, which were stimulated by the addition of straw. This “double strike” approach was particularly efficient under strong temperature variations. Our findings have practical importance and should be considered when attempting to mitigate N losses through the application of straw and NI.