The Composition and Organic Carbon Distribution of Organo-mineral Complex in a black Soil as Influenced by Land-use Change and Long-term Fertilization

Abstract

The aim of this experiment was to examine the impact of natural vegetation restoration and long-term fertilization on the composition and organic carbon distribution of organo-mineral complexes in a black soil. The results showed that the fine sand-size complex was the dominant particle of different size complexes. Contents of silt-size and fine sand-size complexes increased in the NP and NP plus animal manure (NPM) treatments, while the content of clay-size complexes decreased as compare with the non-fertilized treatment (NF). The contents of silt-size and clay-size complexes in the grassland (GL) and the bare land (BL) were the same as that in NF. Landuse change resulted in different dynamics in C sequestration in soil, which made cumulative CO₂ emissions differ significantly among the five treatments during the growing seasons. The content of <20 μm size complex in GL was more than those in NP and NPM. The GL has a potential of sequestering more C than tilled soils due to the stability of SOC stored in the <20 μm size fraction. The cumulative CO₂ emissions increased in the order of NP < GL < NPM. Long-term application of organic manure and vegetation restoration increased the organic carbon content of all sizes of complexes, but increased the cumulative CO₂ emissions. Nevertheless, these soil management practices have substantially increased C sequestration into the soil rather than net C losses.