Effects Of Conservation Tillage On Soil Microbial Properties And Physical And Chemical Characteristics Of Wheat Field

Research was done in agronomy field in Shandong Agricultural University in 2005-2006. The effects on soil microbial prosperties and soil physical and chemical characters were studied of four conservation tillage patterns including subsoiling tillage with straw returned (shorted for SS), harrow tillage with straw returned (shorted for HS), rotary tillage with straw returned (shorted for RS), no tillage with straw covered with straw covered (shorted for NS) and conservation tillage with straw returned (shorted for CS), with conservation tillage with no straw returned (shorted for CN) as a contrast. The aim was to clarify the relationships between tillage patterns and soil microbial characters, enzyme activity and soil nutrients, and to supply academic base for tillage patterns with high efficiency.First, effects of conservation tillage on soil microbial properties. CS could significantly increased soil microbial biomass C at sowing stage, over-winter stage and getting-up stage, and reduced soil microbial biomass C at later stages, which showed that straw returning could regulate soil nutrients. Compared with CN, minimum tillage with straw returning especially RS and SS had higher ability of regulating soil nutrients when balanced soil microbial biomass C at anthesis and maturity stage. Conservation tillage patterns especially NS and HS had higher ratio of microbial biomass C and thus had higher ability of resisting degradation. But further research was still needed in effects of tillage patterns on soil microbial biomass C. The results showed that conservation tillage had higher soil active microbial biomass than CS, higher than CN, straw returning could increase soil active microbial biomass. Conservation tillage could increase soil active microbial biomass in 0~10cm soil layer.Soil microbial activity in 0~10cm in conservation tillage was higher than that of conventional tillage. Straw returning could increase soil microbial activity. Seen from the whole growth stage, SS had the highest microbial activity, reached to 1.008mgCO2/h/kg, and it had good ability of regulating soil nutrients. Straw returning and conservation tillage could only reduce soil respiration rate at the later stages after tillage. Analyse showed that soil respiration was maily mainly affected by soil microbial activity.NS had higher respiratory quotient at 10~20cm, thus younger microbiology, and CN had younger microbiology at 0~10cm. This was good to sustain soil qualified characters and sustainable potentiality. This showed that mechanic tillage and biological tillage were of the same importance in some degree. It was important for reducing energy cost to enhance the effect of microbiology in soil nutrtient transferring.Second, effects of conservation tillage on soil enzyme activities. SS had higher urease activity and sucrase activity in 0~20cm soil layer. Compared with CN, CS could increase urease activity and sucrase activity in 0~20cm soil layer. CS could increase urease activity in 10~20cm soil layer, 14.7% higher than CN. At over-wintering stage when straw was decomposing quickly, CS significantly increased soil sucrase activity and catalase activity.Compared with conventional tillage, except HS, all the other conservation tillage patterns could increase catalase activity, among which NS had the highest ability of eliminating H2O2 in soil of 0~20cm.Third, effects of conservation tillage on soil physical and chemical characters. The pH value of SS was benefit to increase soil microbial activity and transfer soil nutrients in 0~10cm soil layer. Compared with CN, CS was good at regulating soil pH value, and thus benefit to the transferring of nutrients. Conservation tillage had higher keeping water ability than conventional tillage, among which NS and HS had higher water content. While SS was benefit for sustainable and stable water supply.Seen from the whole growth stage, conventional tillage was good for the supply of NO3--N in 0~20cm soil layer, and the leaching loss was little. Conservation tillage had large NO3--N leaching loss amount, but good for the supply of NH4+-N in 0~20cm soil layer, thus was good for the sustainable supply of nitrogen.The results showed that conservation tillage had higher available P content than CN. Except NS, all the other conservation tillage had higher available P content than CN.Conservation tillage increased soil organic matter by a bigger extent than conservation tillage from sowing stage to harvesting stage. Compared with CN, CS increased soil organic matter by 4.58%. Conservation tillage and CS enhanced soil resistance ability, while CN had the trend of reducing soil resistance ability.Compared with CN, SS and CS could increase soil total N content and total P content. Conventional tillage had higher ability of fixing soil N and P, which was not good for the releasing of N and P. While conservation tillage was good for the release of N and P in soil, among which NS and RS were better.The stratification ratio of 0~10cm to 10~20cm of soil nutrients fom big to small was total P, organic matter and total N.Four, effects of conservation tillage on wheat yieldCompared with CN, SS increased winter wheat yield by 11.0%, HS increased winter wheat yield by 10.9%, and difference was significant. CS increased winter wheat yield by 4.30%, and the difference was not significant. While NS reduced yield by 2.45%, and the difference was not significant. The reason why SS and HS had higher yield was the coordinated development of spike number, grain number per spike and 1000 kernels weight. While the reason why NS had the lowest yield was that the spike number and 1000 kernels weight were significantly lower than other treatments. Path analysis showed that NH4+-N had the highest coefficients to yield, and total N followed behind it, while pH value and microbial biomass C had negative relationships to yield, which showed that too high pH value was not good to the supply of soil nutrients, and microbiology had regulated effects on wheat yield.In the condition of this experiment, considering wheat yield, soil microbial properties and physical and chemical characters, SS and HS were better treatments than others.