The Influences Of Tillage And Application Of Microbial Inoculants On Soil Chemical And Biological Characteristics In Rotation Of Wheat And Corn

Crop straw is the fourth of energy resource in the world. If the straw is burned after crops harvesting, it will produce plenty of CO2 into the atmosphere and make an environmental issue. Therefore, more research concerns the straw returning to the field and straw decomposition in soil around the world recently. However, the straw returning to the field should influence chemical and biological properties of soil, such as soil microbial biomass, soil enzyme activities, and nutrients in soil. So this study was conducted in high-yield field located in the piedmont plain of Hebei province under the conditions of straw returned to explore the influences of influences of tillage, straw returning and the application of microbial inoculants on soil microbial biomass, the activities of related soil enzymes and available nutrients in soil during the rotation of winter wheat and maize. The main results showed as follows:1. Deep tillage was more beneficial to decompose the crops straw in soil during next growing season comparing to rotary tillage (normally the depth less than 15 cm) before wheat sowing. For the deep tillage treatment, the application of biogas slurry and EM Strain had accelerated the activities of soil enzymes at each growing stages of winter wheat. Under rotary tillage, the application of biogas slurry, EM Strain and plant growth-promoting rhizo-bacteria improved the activities of cellulose which is closely related to the decomposition of straw manure.2. Compared with the application of silicate bacteria, soil microbial biomass C increased by the application of plant growth-promoting rhizo-bacteria in 0-20 cm soil layers, and soil microbial biomass N was increased by the application of plant growth-promoting rhizo-bacteria in 20-40 cm soil layers. The application of silicate bacteria combined with potassium fertilizer (KCl) decreased the levels of soil microbial biomass C and inhibited the activities of soil cellulase, which was not good for decomposition of straw in soil. Moreover, silicate bacteria had no effect on the concentrations of available K in soil. The application of plant growth-promoting rhizo-bacteria accelerated the decomposition of corn straw in soil during wheat growing period.3. There was no significant difference in microbiologic and biological soil characteristics between straw-stubble mulching and straw-crushing mulching during corn growing period. The two ways of straw returning and the application of microbial inoculants did not enhance the decomposition of straws markedly. Soil microbial biomass C & N increased in 0-20 cm soil layer when bacterium W1 applied and increased in 20-40 cm soil layer when bacterium W2 supplied in soil. Straw-stubble mulching is the better way to decompose the wheat comparing to straw-crushing mulching. Moreover, bacteria W1 and W2 both can accelerate the decomposition of straws.