Effects of long-term fertilization and residue management on soil organic carbon changes in paddy soils of China: A meta-analysis

Quantification of changes in soil organic carbon (SOC) and SOC stock as influenced by fertilization practices is needed for the improvement of carbon (C) sequestration and soil quality. A meta-analysis of 582 paired-treatment data from 95 long-term field experiments published from 1980 to 2012 was used to characterize the changes in SOC under different fertilization treatments and residue management practices in China's paddy soils. All treatments sequestrated significant amounts of C compared with the control (CK, no fertilizer application). The greatest mean difference in SOC change rates was measured in the NPKM (mineral nitrogen, phosphorus and potassium plus manure) treatment, i.e., 0.401 g kg(-1) yr(-1), followed by the M (manure only) treatment (0.36 g kg(-1) yr(-1)), while the N (mineral nitrogen only) treatment caused the lowest rate of 0.046 g kg(-1) yr(-1). The rates of SOC change in the fertilization treatthents with C incorporation (e.g., manure application or straw return) were noticeably higher than those treated with inorganic chemical fertilizers only. The mean difference in the SOC change rates decreased with time and duration of the experiments. The effects of the initial SOC content on the rates of SOC change were not significant, and the effects of SOC accumulation originating from the fertilization treatments depended on the cropping systems. Potential SOC sequestration estimates were more accurate when two factors (sequestration duration and SOC saturation level) were taken into consideration. Our results indicate that the application of manure (e.g., M or NPKM) showed the greatest potential for C sequestration in agricultural soil and produced the longest SOC sequestration duration (45-51 yr). (C) 2015 Elsevier B.V. All rights reserved.