溶质类型与矿化度对半干旱盐渍化地区果园土壤水分有效性的影响

盐渍化土壤水分有效性是制约土地生产能力的关键因素之一。研究不同盐分类型及矿化度的盐溶液对土壤水分有效性的影响, 可为微咸水合理灌溉以及促进土壤生产潜力的发挥提供科学依据。本研究采用离心法在室内研究了脱水过程中灌溉水的溶质类型(NaCl和Na₂SO₄)与矿化度(0、1 g·L^-1、3 g·L^-1、5 g·L^-1、10 g·L^-1)对半干旱盐渍化地区果园土壤水分有效性的影响。结果表明: 不同矿化度的NaCl和Na2SO4处理均可使田间持水量、暂时萎蔫系数、永久萎蔫系数、迟效水和无效水较对照有所降低。不同矿化度的NaCl处理以及1 g·L^-1的Na₂SO₄处理土壤全有效水和速效水都较对照增加, 3 g·L^-1、5 g·L^-1和10 g·L^-1的Na₂SO₄处理土壤全有效水和速效水都较对照减小。不同矿化度的NaCl和Na₂SO₄处理均可使土壤通气孔隙和毛管孔隙相对减少, 非活性孔隙增大, 其中矿化度为5 g·L^-1的NaCl和Na₂SO₄处理对其影响最为明显, 通气孔隙分别较对照减小16.8%和14.8%, 毛管孔隙分别较对照减小5.2%和6.5%, 非活性孔隙分别较对照增加15.7%和14.4%。NaCl对于土壤比水容量和毛管断裂的延迟效果比NaSO₄明显。且土壤溶液盐分含量增加, 土壤持水能力下降、供水性能增加而土壤抗旱性降低。

Effect of solute type and salinity on soil water availability in orchards in saline semiarid regions

Soil water availability is a key factor that restricts land productivity in saline soils. Scientific studies of the effects of solutions with different solute types and salinity degrees have been used to evaluate the application of brackish water on soil salinity and productivity. In this study, the effects of different solute types (NaCl and Na₂SO₄) and salinity degrees (0, 1 g·L^-1, 3 g·L^-1, 5 g·L^-1, 10 g·L^-1) on soil water availability in orchard soils in semiarid saline regions were determined using the dehydration centrifugal method. Soil pore was determined during "conception pore" dehydration instead of "inter-granular pore" and "texture pore" dehydration. This was because soil water loss for the same base membrane properties and structural arrangement was different under different solute types during dehydration. The results showed that compared with the control (CK), treating soils with different degrees of salinity of NaCl and Na₂SO₄ solutes decreased soil field capacity, temporal wilting coefficient, permanent wilting coefficient, slow available water and unavailable water. The contents of total available water and available water of treatments with different salinity degrees of NaCl and 1 g·L^-1 of Na₂SO₄ increased compared with CK. However, the contents of total available water and available water of treatments with 3 g·L^-1, 5 g·L^-1 and 10 g·L^-1 of Na₂SO₄ decreased. Soil aerated porosity and capillary porosity of treatments with different salinity degrees of NaCl and Na₂SO₄ decreased, while inactive porosity increased. Treatments with 5 g·L^-1 of NaCl and Na₂SO₄ decreased aeration porosity by 16.8% and 14.8%, decreased capillary porosity by 5.2% and 6.5%, increased inactive porosity by 15.7% and 14.4%, respectively, compared with CK. The effects of treatments with NaCl on soil specific water capacity and lagging capillary rupture were more significant than treatments with Na₂SO₄. With increasing concentration of salts solution, soil drought resistance and soil water-holding capacity decreased while soil water supply improved.