中文摘要：

【目的】灌溉是设施土壤水分的主要来源,也是影响土壤结构稳定性的重要因子。探究不同灌水控制下限对设施土壤团聚体分布特征和稳定性的影响,为设施农业合理水分调控、促进设施土壤结构改善提供理论依据。【方法】选用6年膜下滴灌试验地为对象,供试作物为番茄（Lycopersicon esculentum Mill.）,种植模式为沟垄覆膜。设置了3个灌水控制下限,其土壤水吸力值分别为20、30及40 k Pa（分别记为D20、D30、D40）,灌水控制上限均为6 k Pa。各小区以埋设深度30 cm的张力计指示土壤水分变化,确定灌水时间和灌水量。通过干筛法和湿筛法测定了土壤团聚体的组成,〉0.25 mm团聚体含量（R0.25）、平均重量直径（MWD）、几何平均直径（GMD）、分形维数（D）、以及土壤结构破坏率（RDS）和不稳定团粒指数（El T）。【结果】在0—30 cm土层,D40处理的土壤电导率（EC）、阳离子交换量（CEC）和容重都显著低于D20和D30处理（D40D30〉D20）（P〈0.05）。通过干筛法和湿筛法对团聚体数量和大小的测定发现,在0—30 cm土层,土壤机械稳定性团聚体主要集中在〉2和1—0.25 mm粒级（23.01%—39.98%）,而水稳性团聚体主要集中在1—0.25和0.25—0.053 mm粒级（31.08—47.27%）。在0—20 cm土层,D30处理的R0.25、平均重量直径（MWD）和几何平均直径（GMD）均高于D20和D40处理;但在20—30 cm土层,D20处理的水稳性团聚体的含量高于D30和D40处理。不同灌水控制下限下的土壤结构破坏率（RDS）和不稳定团粒指数（El T）随土壤深度增加而增加,且RDS与El T的变化规律相似。在0—20 cm土层,D30处理的土壤结构破坏率（RDS）和不稳定团粒指数（El T）显著低于D20和D40处理（P〈0.05）。但在20—30 cm土层,D20处理的土壤结构破坏率（RDS）比D30和D40处理分别低了12.2%和16.8%。干筛下在10—20 cm土层内,D20、D30、D40处理的分形维?

英文摘要：

【Objective】 Irrigation is the main source of soil moisture and affects the soil structure stability under greenhouse condition. The objective of this paper is to explore the effects of different controlled irrigation low limits on composition and stability of soil aggregates in a greenhouse soil. Results of the study will provide a theoretical basis for reasonable water regulation and improvement soil structure.【Method】The irrigation experiments were conducted in a greenhouse at the scientific research base of Shenyang Agricultural University, China during the period from 2011 to 2016. The test crop was tomato, and the planting mode was ridge and furrow covering. Different controlled irrigation low limits were set to： 20 k Pa（D20）, 30 k Pa（D30）, 40 k Pa（D40）, respectively, and the irrigation allowable upper limit of them was set to 6 k Pa. Soil water suctions detected by tensiometers were placed in 30 cm soil layer. The aggregates amount, macro-aggregate content（R0.25）, geometric mean diameter（GMD）, mean weight diameter（MWD）, structure deterioration rate（RDS）, unstable aggregates index（El T）and fractal dimension（D） were examined by dry and wet sieving methods. 【Result】 In the 0-30 cm soil layer, the electrical conductivity（EC）, cation exchange capacity（CEC） and soil bulk density in D40 treatment were significantly lower than those of D20 and D30 treatments（D40D30D20）. The p H value of D20 treatment was significantly lower than that of D30 and D40 treatments（P〈0.05）. In the 0-30 cm soil layer, the size class of dry-stable aggregate was mainly composed of 2 mm and 1-0.25 mm（23.01%-39.98%）; the size class of water-stable aggregate was mainly composed of 1-0.25 and 0.25-0.053 mm（31.08%-47.27%）. In the 0-20 cm soil layer, R0.25, GMD and MWD in D30 treatment were significantly higher than those of D20 and D30 treatments. While in the 20-30 cm soil layer, the wet stable aggregate content of D20 treatment was significantly higher than that of D30