Effects of fertilization on soil organic carbon and carbon pool management index

As an essential indicator of soil quality, soil organic carbon (SOC) and its carbon pool management index (CPMI) had an important role in determining the reasonableness of fertilizer application scheme. The field experiment was conducted to study the influence of different fertilization system on SOC, active organic carbon (AOC) and CPMI under a summer maize cropping system in North China. The experiment included five treatments：1) no fertilizer (CK); 2) organic fertilizer only (OF); 3) recommendation fertilizer (RF); 4) conventional fertilizer (CF); 5) chemical fertilizer only（NPK）. The results showed that compared to CK treatment, SOC and AOC contents increased by 11.68% and 21.71% respectively under OF treatment. SOC contents increased by 6.57% and 7.58% respectively under RF and CF treatments, and AOC contents increased by 8.53% and 4.26%. However, SOC and AOC contents had no obvious enhancement under NPK treatment; OF and RF increased CPMI in comparison with CK by 31.79 and13.01 respectively in soil, while CPMI had no evident change under NPK treatment; The content of AOC in soil were significantly positively correlated with the content of SOC, CPMI and corn grain yield. CPMI had significantly positively correlativity with corn grain yield, and will be a good index to assess influence of fertilization practice on soil quality. It was concluded that under the condition of local soil fertility, application of organic fertilizer, combined application organic fertilizer and chemical fertilizer can both increase SOC contents and improve CPMI, favoring soil quality amelioration and soil fertility improvement.