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非饱和土壤上水势的测定有土柱法、吸引法、张力计法、压力板法、离心机法、蒸气压法、石膏块法、稳定土壤含水量剖面法等数种,现着重介绍使用价值较大的五种测定方法。一、土柱法(或砂柱法)1.结构(1)土柱法:将采集原状土(或扰动土)的φ5cm、高5cm的金属圆筒(或塑料圆筒)重迭起来,接头用乙烯绝缘带密封,成为所要高度(以100cm为限)的纵列(图1)。水分平衡后切开接缝,测定各个高度H所持的水分。(2)砂柱法:将采集的原状土(或扰动土),放在上铺滤纸的能通过0.25mm筛的砂柱(若用石英砂,用50～80目或80～150目)上,下设排水口,水槽应比砂柱高10cm,在试验前可放水使土样达到饱和,上盖塑料薄膜或加盖(图2)。
The determination of water potential in unsaturated soil includes soil column method, suction method, tensiometer method, pressure plate method, centrifuge method, vapor pressure method, gypsum block method, stable soil moisture profile method, etc., and now focuses on the use value. The larger of the five methods of measurement. 1. Soil column method (or sand column method) 1. Structure (1) Soil column method: The metal cylinder (or plastic cylinder) of φ5cm and 5cm in height that is used for collecting undisturbed soil (or disturbed earth) is overlapped. It is sealed with a vinyl insulating tape and becomes a column of a desired height (100 cm) (Fig. 1). After the water balance, the joints were cut and the moisture held at each height H was measured. (2) Sand column method: the collected undisturbed soil (or disturbed soil) is placed on a sand column that can pass 0.25 mm sieve (if using quartz sand, 50-80 mesh or 80-150 mesh) on top filter paper. Drain outlets shall be provided. The sink shall be 10cm higher than the sand column. Before the test, the water may be drained to saturate the soil sample and covered with a plastic film or capped (Fig. 2).