Cropland soils in China have a large potential for carbon sequestration based on literature survey

Abstract

The carbon sequestration of soils has been of key concern particularly since the 4 per mille initiative was launched in COP21 in Paris. Here, we tried to understand three related important questions through literature survey: how did soil organic carbon (SOC) stock change in Chinese croplands in the past decades? What are the agronomic management practices and their potentials to increase the SOC of croplands in China? And how do changes in the SOC affect crop yields? The analyses showed that the SOC stock in the surface soil (0–20 cm) of Chinese croplands increased on average by 0.48% yr–1 from 1980 to 2011. The increase was significant in the eastern and northern China, and particularly in the paddy soils in southern China; however it decreased in the northeastern China. The increase of the SOC stock was attributed to substantial increase in organic inputs, resulted from increased crop productivity, the amendments of crop residues and organic manure, the increases in synthetic fertilizer application and the optimal combination of nutrients, as well as adopting no-tillage practice. Increase in the SOC can increase crop yield and reduce yield variability. Additional means to enhance soil carbon sequestration can be application of biochar, and improvement of synthetic nitrogen use efficiency through disseminating formula fertilizer application based on soil testing, optimized application of inorganic and organic fertilizers associated with extension of conservation tillage. Currently, the straw return ratio has reached about 50%, whereas organic fertilization and conservation tillage (about 6.6%) are still at relatively low levels, the recommended management practices can be further extended to the regions with degraded soils and high population pressure. Further implementation of the recommended management practices on Chinese croplands would increase the SOC stock by ≥25.0 Tg C yr–1 or 0.63% yr–1, compensating for Chinese CO2 emissions by ≥1.0%. In conclusion, Chinese croplands can meet the 4 per mille target and play a crucial role in food security, carbon sequestration and greenhouse gas (GHG) mitigation. The priority is to develop climate smart agronomic management practices to gain synergies between climate adaptation and mitigation.