Effects Of Straw Returning To The Field On The Soil Nutrients, Microbial Biomass And Enzymatic Activity

To explore the effect of crop residues returning to the soil and the methods of fertilizing,, the change of soil nutrients, microbial biomass and enzymatic activity in lime concretion black soil were studied under the condition of returning wheat and maize straw to the field and fertilizing in HuaiBei area of Anhui province by the method of field experiments. The results showed that:returning stalks into field and fertilizing at the same time significantly improved the soil nutrient content, but also increased the microbial biomass, enzymatic activity and soil respiration rate. The main results were as follows:1. Straw returning and fertilization can significantly increase soil nutrients, and influence soil total nitrogen content. At harvest period of corn in2008,total nitrogen content of soil for the treatment of double cropping straw returning and fertilizing was higher of15.3%than the control treatment, higher4%than the treatment of only fertilization, higher12.1%than the treatment of only straw returning. Soil organic matter content of the treatment for double cropping straw returning and fertilizing was higher of29.2%than the treatment of control at sowing stage of wheat, and its maximum increment of soil available P was10.63mg/kg compare with the treatment of control.2. Due to increment of soil organic matter, nitrogen, phosphorus and other nutrient content, soil microbial biomass can also increase. Microorganism can promote transformation of nutrient elements in favor of growth for crop. The soil microbial biomass carbon, nitrogen and phosphorus have increased substantially in the treatment of double cropping straw returning and fertilizing. Compare with the control treatment, its maximum increment was respectively33.7%,74.4%and72.4%. The increment of soil microbial biomass for the treatment of single cropping straw returning to field and fertilization and for the treatment of only fertilization was relatively low.3. Straw returning and fertilizing can significantly improve the soil alkaline phosphatase, urease, invertase, catalase activity, particularly in the late periods of crop growth. Compare with the control treatment, the increment of soil alkaline phosphatase, urease, invertase, catalase activity in the treatment of double cropping straw returning and fertilizing were1.03mg/kg soil soil2h,26.97mg/lOOg soil-3h,1.04mg/g soil-24h and0.1ml/g.4. Straw returning to the field can increased soil respiration rate. The soil respiration rate for the treatment of double cropping straw returning and fertilizing was higher than other treatment. Compare with the control treatment, the soil respiration rate for the treatment of single cropping straw returning to field and fertilization or only fertilization or only straw returning was slightly high.