干旱区绿洲耕地撂荒与复耕对土壤水力性质的影响

土地利用变化会改变土壤质地与结构，影响土壤水力性质，进而改变土壤水分有效性，影响植物生长。由于区域气候的干湿交替与水资源利用效率的提高，干旱区绿洲耕地普遍存在着撂荒-复耕现象。为了明确干旱区耕地撂荒与复耕对土壤水力性质的影响，以民勤绿洲北部边缘的耕地、撂荒地与撂荒复耕地为研究对象，测定0—40 cm深度土壤理化性质，分析不同土地利用下土壤水力性质差异及其影响因素。结果表明：耕地撂荒导致0—40 cm深度黏粒与粉粒比重增加，有机质含量降低，容重降低（P<0.05），土壤孔隙度显著增加（P<0.05），犁底层消失；在高水势阶段，土壤持水与导水能力增强，在土壤有效含水量对应的水势阶段，土壤持水与导水能力变差，有效含水量显著降低（P<0.05）。撂荒地复耕后，0—40 cm深度黏粒与粉粒含量继续增加，有机质含量转而增加，容重增加（P<0.05），土壤孔隙度降低（P<0.05），犁底层重新出现，土壤持水与导水能力又逐渐趋向于耕地水平。撂荒对干旱区绿洲土壤肥力与蓄水能力的提升不显著，而留茬免耕、深耕灭茬还田等保护性耕作措施能有效提高持水能力。利用研究区易测的土壤黏粒、砂粒含量与土壤容重，采用多元线性回归方法，可以准确、快捷预测土壤水分常数，这将有利于研究区农田灌溉制度的准确制定与优化，以及耕地利用变化对土壤水力性质影响的快速评估。

Effects of abandonment and recultivation of farmland on soil hydraulic properties in a typical oasis of arid regions

Land use/cover changes would lead to the change of soil texture and structure， soil hydraulic properties and soil water availability， which would further impact the plant growth. As the fluctuation of dry and wet climate at regional scales and the variation of water utilization efficiency， the abandonment and rehabilitation of farmland were taken place widely on the edge of the oasis in the arid region. Here we focused on investigating the effects of abandonment and recultivation of farmland on soil hydraulic properties in the arid land， and taken the cultivated land， adjacent abandoned land， and re-cultivated land of the Northern margin of Minqin oasis as the research targets. The differences of soil hydraulic properties and their influencing factors in the root zone of three underlying surfaces were analyzed by measuring the soil physical and chemical properties at 0-40 cm depth. We found that the abandonment of cultivated land result in a number changes in soil properties such as the increase in the proportion of clay and silt in 0-40 cm depth， the decrease in soil organic matter contents， the decrease of bulk density significantly lower （P<0.05）， the increase of soil porosity significantly （P<0.05）， and the disappearance of plow layer. Meanwhile， there was an improvement of soil water holding capacity and water-conducting capacity in the high soil water potential stage， and a decrease of the soil water holding capacity and water-conducting capacity in the soil water potential stage corresponding to the available soil water content. The maximum available soil water content decreased significantly （P<0.05）. In contrast， the rehabilitation of abandoned land led to the increase of clay and silt contents in 0-40 cm depth， the improvement of in soil organic matter content and the significant increase of bulk density （P<0.05）， and also the decreasing of soil porosity （P<0.05）. There was a recovery of the bottom layer of the plow， the soil water holding capacity and water-conducting capacity gradually， which was close to the perennial cultivated land level at different soil-water potential stages. This demonstrates that abandonment has no significant effect on the improvement of soil fertility and water storage capacity in the arid oasis， while conservation tillage measures such as stubble-remaining no-tillage， deep tillage， and stubble-destroying returning can effectively improve soil fertility and water holding capacity. The soil moisture constant can be predicted accurately and quickly by using easily measured soil physical properties， such as the soil clay and sand content and soil bulk density by the multiple linear regression method in the study area. It will be beneficial to the accurate formulation and optimization of farmland irrigation system in the study area， and the rapid evaluation of the influence of cultivated land utilization / change on soil hydraulic properties.