Soil organic carbon pools under long-term mineral and organic amendments: a multisite study

Soil organic carbon (SOC) has various pools with different stabilization mechanisms. It is unclear how these SOC pools respond to various mineral and organic amendments depending on a large climate-soil gradient. Here, we studied in three zonal soils: Ferralic Cambisol (subtropic), Calcaric Cambisol (warm-temperate) and Luvic Phaeozem (mid-temperate) under 23-year mineral, straw and manure amendments. Six SOC sub-pools were isolated: unprotected, physically, chemically, biochemically, physico-chemically and physico-biochemically protected pools. Compared to initial level, SOC and most sub-pools increased in the three soils under manure application (p < 0.05), but little under straw and mineral amendments. The Luvic Phaeozems had much higher sequestration efficiencies of bulk SOC (27 • Manure amendments fed SOC and most pools much better than straw and mineral fertilizers. • Luvic Phaeozems had higher build-up ability of SOC pools than the other two soils. • Physico-chemical and physico-biochemical pools had convergent build-up abilities among soils. • Calcaric Cambisol has dissimilar fractionation pattern of SOC with other two soils.