Changes in soil aggregation characteristics and the sequestration of carbon and nitrogen after long-term slight nighttime warming in the farmland of central China

Summary The impact of long-term nocturnal warming on soil aggregate stability and carbon (C) and nitrogen (N) sequestration was examined in agricultural fields. Employing a passive warming system, the nighttime warming experiment involved two treatments: a control check (CK) and a nighttime warming treatment (WT), spanning the entire growth seasons of wheat from 2013 to 2021. The annual average temperature increase ranged from 0.3 to 1.3°C, with an average increment of 0.71°C over the eight years. Both dry and wet sieving methods showed that nighttime warming reduced the proportion of macroaggregates and increased microaggregates compared to CK, thereby diminishing soil aggregate (SA) stability. While nighttime warming had the potential to elevate the concentrations and contents of soil organic carbon (SOC) and total nitrogen (TN), significant effects were only observed in the concentrations and contribution rates of SOC and TN. The C/N ratios across different particle sizes within SA were not significantly affected by nighttime warming. Additionally, no significant correlation was found between the SOC/TN contents and contribution rates and the stability of SA. These results suggest that eight years of nighttime warming could undermine the stability of SA, yet it did not impact the pools of N and C in the agricultural lands of central China.