Abstract: 【Objective】 The study of soil quality after orchard established on slope cropland is of importance to exploration of the soil quality evolution and its evaluation during the agricultural production in loess hilly region.【Method】 Orchard at different years in loess hilly region was chosen as the subject to reveal changes in soil quality through experimental analysis and statistical method, and the slope cropland was used as reference. 【Result】 The results showed that soil physical properties and anti-erodibility did not change markedly or had a little decrease at the early stage of the land use from slope farmland to orchard, then improved significantly with the following years, and kept stable from 20 to 30 years. Soil organic C, total N content increased slowly with the years and reached the peak from 20 to 30 years. Available N improved significantly after 2 years and then increased gradually. Total P and available K dropped at the early stage of restoration and then increased, reached the peak from 20 to 30 years. Available P had no significant change in the first 10 years. The value of pH increased at first but then dropped, which was opposite to CaCO3. The content of soil microbial biomass C increased significantly at the early 5 years and then kept stable, soil microbial biomass P did not vary at the early 10 years and then increased markedly. Basal respiration increased drastically 10 years later and substrate-induced respiration increased significantly 5 years later, then kept stable. Metabolic quotient dropped markedly compared to slope cropland at the early stage but gradually improved with the increase of years, 15 years later, tended to be stable. Urease, alkaline phosphatase, saccharase and cellulase activity increased slowly at early stage and kept stable in 20-30 years. Catalase activity took on wave-like increase, amylase and polyphenol oxidase generally tended to slow drop with years and then kept stable from 10 to 30 years. Soil quality index (SQI), an integral indicator reflecting soil phyico-chemical and biological properties, increased markedly in the early 20 years and kept stable in 20-30 years. Regression analysis showed that SQI took on linear increasing with years (r=0.946). 【Conclusion】 The slope farmland had a low content of soil quality (including physico-chemical, biological properties) due to improper tillage practices and heavy erosion. Compared with slope cropland, soil quality improved quickly at the early stage of orchard and tended to be stable with the following years. The ecosystem of orchard faced a strong ecological stress because of its high output based on a high input.

Key words: Loess hilly region, Artificial orchard, Soil quality