Abstract: Aims Cropping practices and fertilizer/organic matter application affects the soil microbial growth and activity. In china, only few studies have been conducted on the influence of long-term fertilizer and organic matter with fertilizer application on the soil biological properties. Our objective was to study the changes in soil biological and biochemical characteristics under a long-term (15 years) field experiment involving fertility treatments (inorganic fertilizers and organic matter with fertilizers) and two crop rotation systems.
Methods In 1990, thirteen different treatments were established in the Drab Fluvo-aquic soil in Beijing for the long-term experiment. Six treatments werechosen in this study. Four were in a wheat-maize rotation receiving no fertilizer (CK), mineral fertilizers (NPK), mineral fertilizers plus farmyard manure (NPKM) and mineral fertilizers with maize straw incorporated (NPKS). One was in a wheat-maize/wheat-soybean rotation receiving NPK (NPKF). The other was abandoned arable land (CK0) growing weeds. The amount of chemical fertilizer per year was N 150 kg•hm^－2, P₂O₅ 75 kg•hm^－2, K₂O 45 kg•hm^－2, manure 22.5 Mg•hm^－2 and maize straw 2.25 Mg•hm^－2. Established methods were used to analyze soil enzymes and soil physical and chemical characteristics. Analysis was done using an integrative method combining correlation and component analyses in SPSS. Important findings The soil organic C (SOC) and total N (STN) content, microbial biomass C (SMB-C) & N (SMB-N), activities of soil invertase, phosphatase and urease, and the ratio of SMB-C/SOC and SMB-N/STN were found higher in long-term (15 years) abandoned arable land than those in cultivated arable land soils. However, the soil metabolic quotient, pH value and bulk density of fallow soil were lower than those in cultivated arable land soils. The soil nutrient concentration, microbial biomass C & N, activities of soil invertase, phosphatase and urease, were higher in treatments with fertilizer application
(NPK, NPKM, NPKS and NPKF) compared to no fertilizer application treatment (CK). The above soil parameters were also found higher in wheat-maize/wheat-soybean rotation cropping system compared to continuous wheat-maize cropping system. Among the fertilizer application treatments (NPK, NPKM, NPKS and NPKF), NPKM had relative higher soil nutrient concentration, microbial biomass C & N, and enzyme activities compared to other fertilizer application treatments. However, the soil metabolic quotient, pH value and bulk density of NPKM were lower than them.