Study On Comprehensive Effect Of Conservation Tillages In Rainfed Field Of Yellow River Basin

According to the problem of bare surface,severe soil loss and low yield in dry farmland of Yellow River, continuous dynamic measurement of the effect of conservation tillage on physical and chemical properties of the soil,soil biological properties,crop growth and soil erosion, compared with conventional tillage, typical dry farmland of Inner Mongolia region in 2004~2007. An evaluation is made on the economic benefit of conservation tillage in the region. The results showed:1,Conservation tillage improved physical properties of the soil,increased the content of soil nutrient and soil microbe quantity, decreased soil erosion, strengthened storage capacity.Leaving stubble straw mulching is more obvious.2,Soil temperature was lower in conservation tillage than conventional tillage.it was 1.5℃the most. Soil temperature tends to alleviation under straw mulching, When low temperature has "increases the warm effect", when high temperature has "the temperature decrease effect"; Leaving high stubble straw mulching, the rate of moisture content of 0～20 cm soil layer was1.05% higher than conventional tillage, and was 0.76% higher than leaving high stubble straw unmulching. Conservation tillage reduced 0～20 cm soil bulk density and solidity, but it increased 20～60cm soil bulk density and solidity, straw mulching can mitigation soil bulk density and solidity.3,Soil content of available N Phosphorus and Potassium respectively increase by 5.15mg/kg,1.08mg/kg,16mg/kg; Soil organic matter,total N,total P and total K respectively increase by 0.36g/kg,0.15g/kg,1.1g/kg, as compared with conventional tillage.4,Leaving high stubble and straw mulching, the numbers of bacteria,fungi,azotobacter,actinomyces and cellulolytic bacteria increased by1.55times,9.66 times,2.85 times,1.38 times,2.36 times, as compared with conventional tillage,on heading stage of oats.5,Growth vigor of oats in conservation tillage was weaker than that in conventional tillage in the previous two years, leaf area index and dry matter accumulation were low;In third year, the yield increased. Leaving high stubble and straw mulching, the yield and economic benefit increased 16.1% and 67.6%, as compared with conventional tillage.6,Conservation tillage can significant reduced soil runoff and decreased soil erosion. Compared with conventional tillage, leaving high stubble and straw mulching, capacity of runoff and soil erosion decreased 53.6% and 65.8%.