Soil Fertility and Agricultural Sustainability Assessment Based On Long-Term Agroecosystem Experiments in China.

Soil organic carbon (SOC) is the basis and core of soil fertility. The concept of sustainable agriculture emphasizes the importance of SOC management for food security, environment protection and climate mitigation. Long-term agroecosystem experiments (LTAEs) can be defined as large-scale field experiments more than 20 years old that investigate crop production, soil quality, and environmental effects of agriculture. 21 LTAE sites were selected to include a wide range of agro-climates, food crop systems and soil types in China. Major treatments were no fertilizer control (CK), unbalanced nitrogen fertilizer (N), balanced nitrogen, phosphorus and potassium fertilizers (NPK), combination of the NPK and manure (NPK+M), and combination of the NPK and straw (NPK+S). SOC content and crop yield dynamics and their relationship were systematically assessed based on the selected LTAEs. Additional straw and especially manure application are important for maintaining or accumulating SOC, and for increasing crop yield and its sustainability index. There is a strong interaction between SOC and crop yield: increase in crop yield increases C input with residue return and thus increases SOC, and increase in SOC enhances crop yield through improving soil fertility. According to statistical results, an increase of 1 g/kg of SOC can enhance grain yield by 0.3–0.5 t/ha in upland area of north China, and by 0.4–0.6 t/ha in paddy area of south China. On average, grain yield stability can increase by 10% to 20% with an increase of 1 g/kg of SOC. Organic amendments should be widely encouraged to sequester SOC and to sustain soil fertility and agricultural production.

Key Words: Soil organic carbon, Soil Fertility, Sustainable agriculture