Study On Soil Biological Fertility Of Different Fertilization Systems

Based on long-term fertilizer experiments in fluvo-aquic soil in Changping, Beijing, the research was carried out from 2004 to 2006 to explore the effects of long-term fertilization systems on soil biological fertility. The main results are as follows:(1) Long-term (15 years) no fertilizer application treatment (CK) or nitrogen fertilizer application only treatment (N) had very low crop yields. The treatment of long-term combined application of N, P, K fertilizers (NPK) could achieve relatively higher crop yield, and the treatment of NPK fertilizers cooperated with organic manure (NPKM) could achieve even higher yield than that of the NPK treatment. Different fertilization systems brought different amount of organic materials into the soil by leaving crop residues. This provided different amounts and quality of organic matters and energy for soil microorganisms, and formed different soil biological fertilities.(2) Different fertilization systems helped form different soil chemical fertilities. CK and N treatments had the lowest soil organic C content. The soil organic C content of NPK treatment was significantly higher than those of CK and N treatments. NPKM treatment had the highest soil organic C content. Application of chemical fertilizer (N, NPK) could increase soil total N content compared with CK. NPK treatment had higher soil total N content than that of N treatment. The application of organic manure had significant effect on increasing soil total N content. A positive correlation between soil organic C & total N content and crop yield was found. The higher the soil organic C and total N content of the treatment, the lower ratio of soil C/N was found. The soil with fertilizer application had lower pH values than the soil with no fertilizer application. NPK treatment had similar soil pH value with N treatment. NPKM treatment had the lowest pH value. The soil temperature was found higher in the lower yield treatments (CK, N) than in higher yield treatments (NPK, NPKM).(3) Different fertilization systems helped form different soil biological fertilities. Application of fertilizers was found an effect of increasing the amounts of soil bacteria and actinomyces but no significant effect of increasing the amounts of soil fungi. The application of chemical fertilizers could increase the amounts of soil nitrogen-fixing bacteria only among the five types of soil physiological function microorganisms. The application of organic manure had significant effect of increasing most of the five types of soil physiological function microorganisms. Application of fertilizers increased the soil microbial biomass C and N and their turnovers. Application of fertilizers could also increase the activities of soil invertase and urea enzymes. A positive correlation was found between the soil microbial biomass C & N, soil invertase & urea enzymes activities and soil organic C, total N content, and crop yield.