| Loess Plateau has been identified as one of two apple's eugenics district due to its unique climate and soil conditions of resources in China. But within the limited precipitation, coupled with the unreasonable soil management practices, drought and poor soil have become an important factor to restrict the development of healthy and sustainable apple industry in the region. Therefore, this study was conducted to findout the effects of conservation tillage on the apple orchards of this region. Different treatments were used, including no-tillage with straw mulch, plow tillage with straw mulch, subsoiling with straw mulch, grass mulch and no-tillage, while plow tillage was used as control.The data was recorded regarding, soil water, environment properties, soil physical and chemical properties and biological characteristics. The effects of conservation tillage on ability of water storing and preserving, content of soil nutrient and availability of soil nutrient were studied.The main conclusions obtained in this study are as follows:(1)The soil moisture contents of different age orchards and grasslands in 0-5m layer were tested, and the results indicate that the soil available water of 10 years old apple orchard in 5m layer began the behavior of over consumption while the soil moisture excessive consumption of 10, 15 and 20 years old orchard in 5m layer were 2.09, 100.65 and 154.51mm. Similarly soil desiccation rates were 0.21, 6.71, and 7.73mm. a-1. The average SDI (soil desiccation index) of 10 and 15 years old apple orchards were up 2(mild desiccation), The average SDI (soil desiccation index) of 20-year old orchard was 66% (moderate desiccation), after 10 years in the orchard there will occur desiccation. 20 years old orchard showed a serious deficit of water and the average SDI between 54-94% (mild or moderate desiccation).(2)Straw mulch treatments and grass mulch treatment decreased soil bulk density, improved the porosity of the soil, increased soil water storage capacity, especially by the treatment of subsoiling with straw mulch. Subsoiling broked the plough pan, significantly reduced the 20-40cm soil bulk density and the soil bulk density of soiling with straw mulching in 20-40cm layer was decreased by 0.1 g.cm-3compared to plow tillage. Experiment carried out three years later, showed that the soil water storage capacity of the treatment of subsoilong with straw mulching increased by 3.1%. The soil moisture content of different conservation tillage treatments were determined and showed that straw mulch improved the ability of water storing and preserving, in May 2008 and April 2009. The soil poundage in 1m layer of no-tillage with straw mulch increased by 53.81mm and 36.4mm, while of subsoiling with straw mulch was increased by 39.65mm and 26.6mm,. Similarly of plow tillage with straw mulch was increased by 34mm and 22.4mm compared to plow tillage.In September 2008 and August 2009, the soil poundage of subsoiling with straw mulch and no-tillage with straw mulch also showed more than plow tillage indicating that the treatment of subsoilong with straw mulching and no-tillage with straw mulch have the strong and preserving ability of water. The treatment of grass mulch decreased the soil bulk density, improved the porosity of the soil and increased soil water storage capacity, however, gross needs to takes a certain degree of soil moisture to grow, so grass competed for water with apple trees in the year or season when the rainfall is less, in May 2008 the soil poundage of grass mulch decreased by 25.75mm compared to plow tillage. In May 2008 and April 2009, the soil poundage of no-tillage more than plow tillage, but lower than plow tillage in September 2008 and August 2009, indicated that the ability of water storing of no-tillage was better than plow tillage and the ability of water impoundment of plow tillage was better than no-tillage.(3)From 2007 to 2009 treatments of straw mulch under different tillages and grass mulch have improved soil organic matter content. In 2008 and 2009, plow tillage with straw mulch, subsoiling with straw mulch, no-tillage with straw mulch and grass mulch increased the soil organic matter in the 0-20 cm soil layer by 4.75 g.kg-1, 4.76 g.kg-1, 4.53 g.kg-1 and 3.35 g.kg-1 compared to the treatment of plow tillage. Treatments of straw mulch under different tillages and grass mulch have improved soil total fertilizer and the increase rate of subsoiling with straw mulch, plow tillage with straw mulch and no-tillage with straw mulch was largest. At the same time after the implementation of conservation tillage in orchard, the actual capacity of the soil for fertilizer has also been greatly improved, in 0-40cm soil layer in 2009, the soil available N content of subsoiling with straw mulch, plow tillage with straw mulch, no-tillage with straw mulch and grass mulch increased by 13.25 mg.kg-1, 12.45 mg.kg-1, 6.17 mg.kg-1, 4.92 mg.kg-1 and the soil available P content of subsoiling with straw mulch, plow tillage with straw mulch, no-tillage with straw mulch and grass mulch increased by33.94 mg.kg-1, 33.08% mg.kg-1, 28.61 mg.kg-1, 12.61 mg.kg-1 compared to plow tillage.(4)Straw mulch under different tillage and grass mulch have increased soil bacteria and fungi compared to plow tillage and effect of subsoiling with straw mulch on increasing soil bacteria and fungi was highest, followed by plow tillage with straw mulch, no-tillage with straw mulch and grass mulch. Affect of treatments on soil enzyme activity same as soil microorganism, effect of subsoiling with straw mulch on the activity of soil sucrase, urease and catalase was highest in al treatments and followed by plow tillage with straw mulch and no-tillage with straw mulch and the difference under treatments was significant. (5)The correlation analysis of soil fertilizer characteristics, soil biological traits results, indicated that soil organic matter content in 0-40cm layer extremely significant correlation with the soil TN content, TP content, TK content, AN content, AP content, AK content, soil sucrase, soil urease , soil catalase, soil bacteria and soil fungi, and negative correlation with soil actionmycete. Principal component analysis on the integrated soil fertility was evaluated and the effect of different treatments on integrated soil fertility were: subsoiling with straw mulch>plow tillage with straw mulch>no-tillage with straw mulch>grass mulch>no-tillage>plow tillage, and also known by the composite scores that the integrated soil fertility scores of subsoiling with straw mulch, plow tillage with straw mulch and no-tillage with straw mulch were above the value, grass mulch below the average but score higher than plow tillage. The results above all indicated that straw mulch and grass mulch play an important role in improving soil fertility.(6) Conservation tillages increased fruit yield and quality of apple, 100 fruit weight of subsoiling with straw mulch increased by 1.11kg, saccharinity increased by 2.27% compared to the treatment of plow tillage; plow tillage with straw mulch and no-tillage with straw mulch increased 100 fruit weight by 0.76kg and 0.88kg, increased saccharinity by 1.74% and 1.79% compared to the treatment of plow tillage.(7) Drought and poor soil was an important factor to restrict the development of healthy and sustainable apple industry in the region. The experiments showed that the effect of no-tillage with straw mulch and subsoiling with straw mulch on ability of water storing and preserving was best and the effect of subsoiling with straw mulch and plow tillage with straw mulch on improving soil fertility was best in all treatments. Integrated soil fertility and soil water effects and to reduce energy for the purpose, the best orchard soil management in the region is subsoiling with straw mulch, and we should pay attention to subsoiling and no-tillage, soil tillage rotation in orchard soil management to improve the soil metabolism and to improve the soil nutrients levels and nutrients availability.
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