Effects of Long-Term Fertilization on Organic Carbon Mineralization of Different Grain Size Components in Paddy Soils from Yellow Earth

Abstract

Organic carbon in different soil components shows different fertility and bioavailability because of the difference in its stability. Studying the mineralization difference of organic carbon in soil components under long-term fertilization can provide basis for understanding soil components stability and carbon cycle theory. Organic carbon with different particle size components as an important medium in the formation process of humu, which strength of carbon sequestration capacity directly affects the difference of carbon storage. Therefore, the definition of the stability of different components organic carbon will inevitably enrich the mechanism of organic carbon in the whole soil. In this paper, the mineralization characteristics of coarse particle component (250–2000 μm), microaggregate component (53–250 μm) and clay particles (<53 μm) under different treatment (no fertilization (CK), chemical fertilizer (NPK), organic fertilizer (M) and constant organic-inorganic fertilizer (MNPK)) were studied by indoor simulated culture test, and potential mineralizable organic carbon and turnover rate were calculated using the first-order kinetic equation. The results showed that the content of organic carbon and potential mineralizable organic carbon were the highest in coarse particle components and the lowest in clay particle components under different fertilization treatments. Organic fertilizer treatment (M and MNPK) significantly increased its content. The trend of organic carbon mineralization rate was the same, which can be divided into rapid mineralization on 3—12th day and slow mineralization on 12–30th day. The release intensity of organic carbon accumulation mineralization decreased with the extension of culture time. The cumulative mineralization rate of organic carbon in all soil components decreased more in organic fertilizer treatment than CK treatment, which was 0.47–0.15 percentage points and decreased with the decreasing fraction. Overall results suggested that the effects of different fertilization treatments on soil components were mainly manifested on larger fraction components. Organic fertilizer can be used as a better choice for carbon storage management and the carbon sequestration capacity of different components increases with the decrease of particle size, and this study can provide an important basis for the soil fertility of yellow paddy fields.