| Aimed to solve bare surface, loose soil, serious wind and water erosion and water use efficiency in dry farmland of Yellow River basin, through field experiments and farmer investigation for three years, the soil physical, chemical and biological properties, crop yield and benefits under condition of conservation tillage were analyzed systematically by combination of traditional analysis and modern molecular biologyical methods.1. Regulation to soil temperature: Soil temperature of conventional tillage is higher than conservation tillage before 3:00 pm, difference is from 0.5 to 1.7℃;while lower from 3:00 pm to 6:00 am, difference is from 1.0 to 2.1℃;Soil temperature's difference became smaller with increasing depth of soil layers; It has great temperature difference among all treatments in sunny day while little in cloudy.Soil moisture's increasing: Conservation tillage are higher than conventional tillage in the whole growth period, which increases 14.99%, 5.90%, 2.45% and 2.89% of low stubble with residue cover, high stubble with residue cover, no-tillage with low stubble, no-tillage with high stubble, respectively.Soil micro-aggregate increasing obviously: small aggregates (<0.01mm) of no-tillage with low stubble, low stubble with residue cover, high stubble with residue cover, no-tillage with high stubble increases by 82.2%, 44.9%, 55.2% and 42.3% respectively, while decreases by 157.8%, 121.9%, 412.6%, 117.6% than that of conventional tillage for big aggregate (>2mm), respectively.It has great effect on bulk density in 0~20cm soil and little on deep soil. By different tillage methods, no-tillage with high stubble, no-tillage with low stubble, high stubble with residue, low stubble with residue increases by 35.3%, 31.1%, 27.7%, 35.5% than that of conventional tillage; Soil bulk density of conservation tillage became smaller while higher than conventional tillage with increasing depth of soil layers.2. Soil nutrient content increasing: organic matter, total N, total P, total K, available P, available K, available N at 0~20cm soil layers increases obviously, which increases by 10.4%~24.1%,17.5%~46.0%,7.1%~33.3%,6.1%~13.2%,18.5%~6.3%,15.1%~35%,1.6%~9.5% than that of conventional tillage in order of low stubble with residues > high stubble with residues > no-tillage with low stubble > no-tillage with high stubble > conventional tillage, respectively.3. Conservation tillage effect on microbe group's quantity, composition, proportion. The account of bacteria, fungi, actinomycetes, cellulose-decomposing microorganisms, azotobacter increases by 43.8%~113.9%, 364.2%~606.5%, 45.3%~99.4%, 18.8%~87.5% and 84.8%~110.3% than that of conventional tillage. Bacterial accounts are 77.95% and 49.73% in total microorganism in conservation and conventional tillage, respectively. The account of fungi, actinomycete, cellulose-decomposing microorganisms, azotobacter's proportions in two methods are different, too. Bacteriawith organic matter, total N, total K, available P, available K and available N, fungiwith total N, total K and available K, azotobacter with total N, total K, total P and available K, cellulose-decomposing microorganisms with total K, total P, available N and available P are all highly significant correlation. Azotobacter's account and nutrient content are not significantly related.4. Compared with conventional tillage, conservation tillage makes soil enzyme activity increased significantly by 2.73%~86.4%, 12.0%~25.5%, 18.8%~85.7% and 29.9%~47.9% for catalase, urease, invertase and ALP activity, respectively. Urease with total N and available N, invertase with organic matter, total N, available N and available K are significant positive correlation. Catalase with total N, total P and available N is highly significant positive correlation.5. Conservation tillage makes soil microbial biomass C, N, P increasing by 18.1%~44.2%, 41.4%~444.5% and 16.0%~26.8% than that of traditional tillage for maize, and increasing 23.9%~36.7%, 38.1%~379.3%, 38.1%~379.3% for oat, respectively. It drops for soil microbial biomass C, increases for soil microbial biomass P and shows a single peak curve for soil microbial biomass N with the postponing of crop growth procedure. There is positive correlation among soil microbial biomass C, N, P with maize yield, while no significant correlation with oat yield.6. According to DGGE Molecular Marker Technology, richness and evenness of soil microbial diversity varies with different tillage methods and different crops. For maize, soil diversity index of high stubble with residue is higher than no-tillage with high stubble, low stubble with residue, and no-tillage with low stubble and conventional tillage are lower. For oat, soil diversity index of conventional tillage is higher than high stubble with residue, no-tillage with high stubble, low stubble with residue and no-tillage with low stubble are lower. In general, the two crops have greatest effect on Soil Microbial Diversity in high stubble with residue.7. Adopted conservation tillage, crop yield shows an increasing trend. Conventional tillage drops by 9.6% and 3.8% than that of conservation tillage in the first year and the second year. In the third year, maize yield in high stubble with residue increases by 6.6% than that of traditional tillage. Surface runoff and soil erosion in high stubble with residue cover, no-tillage with high stubble decrease than conventional tillage by 32.2%～72.3%,38.4%～75.6%, respectively.According to Cluster Analysis and Principal Component Analysis, it shows that urease, invertase, total N has a great effect on contribution rate of maize yield and organic matter, total P, available P and catalase take second place. Net income of conservation tillage increases 1516 yuan/hm2 and 13.0% than that of conventional tillage.
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