Long-term fertilization increases the temperature sensitivity of OC mineralization in soil aggregates of a highland agroecosystem

Abstract

The mineralization of aggregate-associated organic carbon (OC) and the effect of long-term fertilization on its temperature sensitivity have not been addressed, but are critical for understanding OC sequestration and dynamics in agricultural soil. We measured the mineralization of OC in total soils and aggregates after 27years of application of various fertilizers in a highland agroecosystem in central China and calculated the temperature sensitivity of OC mineralization. Our objectives were to understand the effects of long-term fertilization on OC mineralization in aggregates and its temperature sensitivity, and to determine the contribution of each aggregate size class to OC mineralization in total soils. Long-term fertilization decreased cumulative mineralized OC (Cmin) in <0.053mm size class but increased Cmin in >2, 0.25–2, and 0.053–0.25mm aggregates. The increases were smaller in treatments with mineral fertilizers than with manure or manure combined with mineral fertilizer. The temperature sensitivity of OC mineralization was decreased in >2mm aggregate but increased in <2mm aggregates and total soils by fertilization treatments. The OC mineralization in <0.053mm size class accounted for 36% of the OC mineralization in total soils. Manure or manure combined with mineral fertilizer had a higher potential to change the contribution of aggregates to OC mineralization in total soils. Our results suggest that OC mineralization in total soils was determined mainly by mineralization in the <0.053mm size class of these highland agricultural soils, and long-term fertilization increased the temperature sensitivity of OC mineralization in total soils and <2mm aggregates.