Effect of household land management in constraining soil organic carbon storage at plot scale in a red earth soil area of South China

摘要

An inventory of topsoil organic carbon content in household farms was performed in a village from a typical rural area with poor soil fertility in a red earth region in Jiangxi Province, South China in 2003. A statistical analysis of SOC variation with land use and household management types, and with crop management practices was conducted. The size of plots surveyed ranged from 0.03 ha to 0.63 ha, with a mean of 0.1 ha, showing consider cropland fragmentation. Topsoil SOC content ranged from 1.72 g/kg to 25.2g/kg, with a mean of 12.7g/kg, varying widely with a variety of household land management and agricultural practices arising from individual household behaviours. Land fragmentation played a minor role in SOC variation with the mean SOC content in plot size <0.1 ha being 20% lower than plot size ≥0.1ha. Nevertheless, the land use (rice fields or dry croplands) and the land contractual system (direct contract or subcontracted land) had greater impacts; SOC content in the plots of dry croplands was 70% lower than that in rice paddies, and the SOC in contracted plots was almost double that found in subcontracted plots. In contrast, agricultural management practices had smaller effects; a 30% increase in SOC with green manure cultivation, and a55% increase with changing cropping intensity. The difference in SOC levels between the least and most favourable cases of household land management and agricultural practice was up to 150%. Our results suggest that policies targeted at agricultural management alone may not deliver the expected SOC benefits if household land management is not also improved. This case study provides rare quantitative information linking limits in the efficacy in soil carbon storage with potential barriers to implementation and may serve as a template for investigating barriers to implementation of climate mitigation practices in agriculture elsewhere in the developing world.