利用环刀法测定土壤水分精度的影响因素

目的]探讨环刀法测定土壤物理性质准确性的影响因素,为批量土壤物理性质准确测定提供参考。方法]以不同类型土壤为研究对象,采用环刀法测定持水量特性,对环刀浸泡水位、浸泡时间、置砂时间及滤纸对测定结果的影响进行讨论分析。结果]水位高于或低于环刀上沿时,土壤均难以达到最大持水量;水位至环刀上沿且浸泡12～14 h后土壤持水量趋于最大;环刀放置在砂上2～2.5 h避免了重力水干扰,毛管水量测定准确稳定,之后环刀持续置砂72～76 h,是测定最小持水量的适宜时段。忽略环刀中滤纸的持水重量会对最大持水量及毛管持水量的测定造成一定偏差,去除其重量有利于提高测定精度。结论]对现有环刀法测定土壤物理性质的试验条件进行优化改进,降低了误差,检测结果具有代表性及可比性,适用于批量土壤样品的检测分析。

Influencing Factors on Measurement Accuracy of Soil Water by Ring Knife Method

Objective] The influencing factors of measuring the accuracy of soil physical properties by ring knife were discussed in order to provide reference for accurate determination of physical properties of bulk soils.Methods] Taking different types of soil as the research object, the characteristics of soil water holding capacity were determined by ring knife method, and the influence of soaking water level, soaking time, sand blasting time and filter paper on the determination results were analyzed.Results] When the water level was above or below the edge of the ring knife, the soil water holding capacity was difficult to reach the maximum. When the water level was along the edge of the ring knife and the ring knife was soaked for 12~14 h, the soil water holding capacity tended to be the maximum. The ring knife was placed for 2~2.5 h to avoid the interference of gravity water, and the capillary holding capacity was accurate and stable. The ring knife continued to be placed for 72~76 h, and the minimun water holding capacity was representative. Ignoring the water holding weight of the filter paper in the ring knife would cause a certain deviation in the determination of the maximum water holding capacity and the capillary holding capacity, and removing its weight was beneficial to improve the accuracy of the measurement.Conclusion] This experiment optimized and improved the existing test conditions for determining soil physical properties by ring knife method, and the test results were representative and comparable by reducing errors. It was suitable for the detection and analysis of batch soil samples.