Particulate Organic Carbon And Enzyme Activities In Long-term Fertilized Black Soils

Long-term different fertilized black soils were sampled at the Key Observation Station of the Harbin Black Soil Ecology, Ministry of Agriculture. Particulate organic carbon (POC) and soil enzyme activity were analyzed to evaluate the effect of different fertilization on the black soil fertility.The soil aggregation was classified using wet sieving method. The soil organic carbon (SOC) and POC in different aggregation were determined by total organic carbon analyzer. The aggregation 2-0.25 mm and 0.25-0.053 are above 70%. Organic fertilizer increases SOC and the stability of aggregation. The stability of aggregation was decreased by inorganic fertilizer. The POC in aggregation >2 mm is much more than other classifications. The POC in aggregation 2-0.25 mm and 0.25-0.053 was increased by organic fertilizer. Organic fertilizer enhanced the carbon sequestration.The activity of Dehydrogenase, Chitinase,α-glucosidase andβ-glucosidase was determined by colorimetric method and the Denitrifying enzyme activity was determined by slurry culture method. The organic fertilizer has a significant effect on the soil enzyme activity. The mixed fertilizer is one of the effective measures to increase black soil enzyme activity. The highest activity is Dehydrogenase with 92.5 mg/ (kg 24h) in sample M1P1, Chitinase with 39.5 mg/ (kg h) in sample M2N2,α-glucosidase with 28.7 mg/(kg h) in sample M1P1K1,β-glucosidase with 234 mg/(kg h) in M1P1K1 and Denitrifying enzyme with 10.9 mg/(kg h) in sample M1N1P1K1. The nitrogen fertilizer and NPK fertilizer increase the activity of Chitinase. The activity of Chitinase has a significant positive correlation with the mount of organic fertilizer. The nitrogen and phosphate fertilizer decrease the activity of Dehydrogenase. Organic fertilizer increased the activity of the Dehydrogenase. The single inorganic or mixed inorganic fertilizer has little effect onα-glucosidase activity, but organic fertilizer significantly increasesα-glucosidase activity. The nitrogen and phosphorus mixed fertilizer has significant effect on theβ-glucosidase activity. Double fertilizer increasesβ-glucosidase activity significantly. The nitrogen fertilizer decreasesβ-glucosidase activity. The nitrogen, phosphorus and organic fertilizers increase the activity of Denitrifying enzyme. The mixture of organic and inorganic fertilizer can enhance the stability of aggregation, sequestrate more organic carbon, increased the activity of soil enzyme. Therefore soils become fertile.