Abstract: 【Objective】The objective of this study is to explore dynamic differences and influence factors of organic carbon mineralization in different types of paddy soil under long-term located fertilization. The results could help us to illuminate the characteristics of organic carbon mineralization in different types of paddy soil and provide guidance for formulating reasonable nutrient management measures.【Method】In this study, the paddy soils in four different places were used, including Changshu (gleyed soils) in Jiangsu province, Yujiang (reddish soil of low fertility) in Jiangxi province, Wangcheng (reddish soil of high fertility) in Hunan province, and Chongqing (purple soil). The soils were collected in long-term fertilization location including three different treatments, as control (no fertilizer, CK), N, P and K fertilizer (NPK), N, P and K fertilizer plus rice straw (NPKS). The organic carbon mineralization laboratory incubation experiment was conducted in 27 days. The cumulative carbon mineralization was measured through alkali absorption method in constant incubator. The Jones first-order kinetic model was used to express the dynamics of cumulative carbon mineralization with respect to incubation time and was fitted to compare the influence of soil type and different applications of long-term fertilization on the dynamics of carbon mineralization.【Result】Long-term fertilization could improve the content of soil total N, P, K and organic carbon but decreased the soil pH. Long-term fertilization could significantly improve the cumulative carbon mineralization (C) except Changshu soil and different fertilizations caused the increase of 11.7%-86.1%. Two parameters in mineralization kinetic equation, potential mineralization of organic carbon (C0) and easy mineralization of organic carbon (C1), could be significantly improved by fertilization in the reddish paddy soil of Yujiang and Wangcheng. In the same fertilization treatment, C, C0 and C1 were bigger in Changshu and Wangcheng while smaller in Chongqing and Yujiang; Ratio of C0 to soil organic carbon (C0/SOC) was bigger in Yujiang. Correlation analysis indicated that soil organic carbon, total nitrogen, available nitrogen and total phosphorus showed a very significant positive correlation with C, C0 and C1 (P＜0.01); pH and total potassium showed a very significant negative correlation with C; C0/SOC showed a significant negative correlation with SOC, pH and all nutrient indexes. The fertilization treatments had no significant effect on mineralization rate constant (k) while the soil type affected k significantly. The k displayed a very significant negative correlation with pH, C/N, total K (P＜0.01) and a significant negative correlation with available K (P＜0.05). The relative influence of different parameters was obtained through aggregated boosted trees and the result showed that available nitrogen and soil organic carbon had a bigger impact on C and C0 with relative influence at 23.8%, 20.2% (for C) and 29.5%, 23.7% (for C0); soil organic carbon and pH had a bigger impact on C1 and C0/SOC with relative influence at 26.7%, 15.9% (for C1) and 34.4%, 23.0% for (C0/SOC); pH and total potassium had a bigger impact on mineralization rate constant (k) with relative influence at 34.2% and 22.1%, respectively.【Conclusion】The type of soil exerted a bigger impact on soil organic carbon mineralization dynamic than long-term located fertilization. The difference of parent material, pH, organic carbon and nutrient content of soil in different long-term fertilization locations account for the dynamic difference of organic carbon mineralization.

Key words: long-term located fertilization, organic carbon mineralization, kinetic equation, aggregated boosted trees, relative influence