Characteristics of Organic Carbon Changes in Brown Earth under 37-year Long-Term Fertilization

To investigate the impacts of different fertilization on characteristics of organic carbon (OC) changes in brown earth (Hapli-Udic Cambisol), an experiment was conducted with long-term located fertilization experiment from 1979–2015. The experiment field divided into chemical fertilization group, low levels of organic manure group and high levels of organic manure group. The results showed that: the OC was mainly stored in >1.0 mm size aggregates. As the organic fertilizers application grew, the mass percentage of the water-stable aggregates (WSA) for >1.0 mm aggregates significantly increased by 2.3–30.1 times and when the organic and inorganic fertilizers were combined to be applied, the mass percentage of >2.0 mm aggregates and carbon preservation capacity (CPC) increased significantly. Over 37 years of fertilization, the organic carbon concentration, stock and rate of change in brown soil presented the following rank: high-levels of organic manures group > low-levels of organic manures group> chemical fertilization group. Based on the experimental data over the last 37 years, we examined the relationship between total carbon input and the change of organic carbon stock, and constructed a curve: y = 0.153x–0.129.