保护性耕作下农田表土有机碳含量变化特征分析——基于中国农业生态系统长期试验资料

本文收集整理1979--2008年有关中国保护性耕作的长期试验文献，整合分析了长期保护性耕作下中国农田表土有机碳的变化特征。采用的48篇有效文献涉及18个省（区、市）的59个长期试验点，涵盖12种土类。总样本88个（其中早地51个，水田37个）。结果表明，保护性耕作处理下旱地和水田表土有机碳年变化分别介于一0．30～0．75g·kg^-1·a^-1和-0．20～2．71g·kg^-1·a^-1，平均增幅分别达0．21g·kg^-1·a^-1和0．51g·kg^-1·a^-1。可见长期保护性耕作下，农田表土有机碳含量总体呈上升趋势，水田下增长高于旱地。和少免耕相比，秸秆还田更有利于促进表土有机碳的积累。统计分析还表明，结合秸秆还田的综合保护性耕作措施可以使水田和早地的有效固碳期限分别持续27a和23a，水田在保持较高固碳速率的同时，延长了有效固碳年限。耕地表土有机碳含量在保护性耕作下特别是秸秆还田可以较大幅度地提高，实行保护性耕作可以具有农业稳产与土壤固碳的双重意义。

Characteristics of Cropland Topsoil Organic Carbon Dynamics Under Different Conservation Tillage Treatments Based on Long-term Agro-ecosystem Experiments Across Mainland China

Conservation tillage （CT）has become one of the most important measures of sustainable agriculture development, and it is a relatively new concept but widely adopted in China and has considerable benefits. In this paper data of topsoil soil organic carbon （ SOC ）in longterm field experiments of China from publications available from 1979 to 2008 was collected to summarize and analyze the dynamics of SOC. The data set comprised of 88 observations （51 and 37 from dry croplands and rice paddies, respectively）of SOC under different conservation tillage measures at 59 experiment sites （31 for dry croplands and 28 for rice paddies）across 18 provinces of mainland China. The soils repre- sented by the experiments covered 12 dominant types of cropland soils from China. The relative increase in SOC content was analyzed with respect to initial SOC stock, and rice paddies and dry croplands soils were compared. This analysis was done for 2 different categories of long-term conservation tillage：no-tillage （reduced tillage ）and straw mulching. An overall increase in SOC was projected for both types of croplands, with a relative annual increment （RAI, g·kg^-1·a^-1）of -0.30-0.75 （0.21 on average ）for dry cropland soils, and -0.20-2.71 （0.51 on average） for rice paddy soils. Initial and final SOC values in rice paddies were higher significantly than that in dry croplands, and rice paddies can enhance SOC accumulation than dry croplands. Enhanced SOC accumulation was much higher under straw mulching than that in no-tillage and reduced tillage. Comprehensive conservation tillage （no-tillage with straw mulching ）contained carbon sequestration durations of 27 and 23 years for rice paddies and dry croplands, respectively. Conservation tillage is a key technique of sustainable agriculture, and carrying out research of application and extension of conservation tillage in China is of profound significance. It is necessary to strengthen the study for improving crop productivity, enhancing SOC accumu