The Rate and Duration of Nitrogen Addition Influence the Response of Soil Heterotrophic Respiration to Nitrogen in Cropping Systems

Under today’s climate warming, mitigating the risks of soil organic carbon (SOC) decomposition in cropping systems is critical to maintain carbon sequestration. This study posits that nitrogen addition rate and duration are the key factors influencing the responses of soil heterotrophic respiration (Rh) to climate warming in a cropping system. Based on soil sampled from traditional-agriculture rice-growing regions in the Taihu Lake Basin in eastern China, this study aimed to clarify how nitrogen addition strategies affect soil Rh and its temperature sensitivity (Q10) and to explore the underlying mechanisms of the changes in soil environment that influence carbon emissions under nitrogen addition through the Rh pathway. The results demonstrate that, with the increasing duration of nitrogen addition, soil Rh and its Q10 were initially increased but subsequently suppressed, and the inhibitory effect on soil Rh became apparent after six years of continuous addition. Further analysis revealed that decreases in C/N, pH, and extractable organic nitrogen and increases in mineral nitrogen are the primary factors suppressing soil Rh. These findings indicate that an optimized nitrogen addition strategy tailored to specific crops could achieve profitable crop yields while effectively mitigating the promoting effect of climate warming on SOC decomposition.