不同时期农田土壤水分和盐分的空间变异性分析

以河套灌区一农田(500m×1100m=55hm2)上55个采样点的水分和盐分作为研究对象,从统计特征值、半方差函数和克立格法绘制的分布图几个方面对比分析了2个时期(即秋浇前和夏灌前)土壤水分和盐分的空间变异性。结果表明夏灌前土壤水分属弱变异性,秋浇前属中等(偏弱)变异性,土壤盐分均属中等变异性;2个时期的水分和盐分都具有空间自相关性,且秋浇前土壤水分和盐分相关性较强,夏灌前二者具有中等强度的空间自相关性,秋浇前土壤水分和盐分的变程(或最大自相关距离)都大于夏灌前。用普通克立格估值绘制的分布图表明土壤水分或盐分在2个时期的分布差别较大,说明秋浇储水、季节性土壤冻融及春季消融时的蒸发对播种前土壤水分和盐分的空间变异性的影响强烈。在北方季节性冻融地区,了解这2个时期土壤水分和盐分的空间分布,对节水灌溉、土壤改良和农田或区域水资源管理等具有指导意义。

Spatial Variability of Soil Water and Salt in Field at Different Time

Data of soil water and salt used in this study were collected at 100 m100 m-spacing nodes of a regular grid on a 55 hm~2 field of Hetao before last fall irrigation and before first summer irrigation. Statistical and geostatistical analyses were conducted to analyze and compare spatial variability of soil water and salt before last fall irrigation and before first summer irrigation. The variability intensity of soil water before first summer irrigation was low, is middle before last fall irrigation. The variability intensities of soil salt before last fall irrigation and before first summer irrigation were middle. Both soil water and salt were spatially auto-correlated for the two periods. Auto correlations of soil water and salt belonged to high intensity before last fall irrigation, middle intensity before first summer irrigation. Correlation ranges of soil water and salt before last fall irrigation were greater than before summer irrigation. Image maps by ordinary Kriging showed distributions of soil water and salt at different times were different, which proved the variability of soil water and salt before first summer irrigation were violently affected by fall irrigation, seasonally soil freeze-thaw law and soil water evaporation in spring. Understanding the distributions of soil water and salt in seasonally frozen districts of northern parts of China is important for saving-water irrigation, soil improvement and management of water resources.