Analysis of effect of soil quality after orchard established in hilly loess plateau | 黄土丘陵区营造果园后土壤质量效应分析

Chinese. 目的研究黄土丘陵区坡耕地营造果园后土壤质量变化过程。方法采用时空互代法，以黄土丘陵区不同年限的塌地果园为研究对象，选取坡耕地为对照，通过室内测试分析，并运用统计和相关分析等方法，研究土壤质量的变化过程。结果坡耕地改造为果园后，在改造初期土壤物理性质和抗蚀性变化不大或略有降低，随后显著改善并趋于稳定。土壤有机碳和全氮含量在改造前10年波动较大，增幅较慢，随后增长加速，15―30年基本趋于稳定；碱解氮含量在改造2年后增幅即达到显著水平，随后逐步升高。全磷和速效钾含量在初期显著降低，随后逐渐上升。速效磷在改造前10年变化不大，随后逐渐升高。pH随改造年限先升高后降低，CaCO3先降低后升高。微生物量碳、氮在改造前5年增幅显著，随后趋于稳定。微生物量磷在改造10年增加达到显著水平，随后逐渐增加。土壤基础呼吸强度在改造10年后显著增加，随后逐渐增加。诱导呼吸强度在改造5年后增幅达到显著水平，随后趋于稳定。代谢商在改造初期显著低于坡耕地，随后逐渐升高，15年后趋于稳定，和坡耕地没有显著差异。土壤脲酶、碱性磷酸酶、蔗糖酶和纤维素酶活性缓慢增加，在20―30年时趋于稳定。过氧化氢酶在改造第2年增幅即达到显著水平，随后随改造年限呈波动式缓慢上升。淀粉酶和多酚氧化酶活性整体随改造时间呈缓慢降低趋势，分别在10年和2年时达到显著水平，10―30年时趋于稳定。土壤质量指数（SOI）作为土壤理化和生物学性质的综合反映，在前20年土壤质量改善作用明显，20―30年趋于稳定，回归分析表明SQI随年限的增加呈显著的线性关系（r=0.946）。结论黄土丘陵区坡耕地由于严重的水土流失和不合理耕作方式，土壤物理、化学和生物学性质较差。改造为塌地果园初期，物理、化学和生物学性质显著改善，SQI增加，改造中后期，系统处于相对的稳定期，土壤物理、化学和生物学特性改善作用有所减缓，SQI趋于稳定。但此阶段却是以高投入高产出的状态在运转，系统仍旧受到较强的胁迫。

English. 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.