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土壤含水量（θv）与电磁波在插入土壤的时域反射仪（TDR）探针中传播时间（T）的半理论、半经验标定曲线θv＝（T／Ta－Ts／Ta）／（Kw0.5－1）通常用于计算土壤含水量。本项试验应用TDR测定了不同质地及不同容重条件下烘干土壤的Ts／Ta值。结果表明，四种被测土壤的Ts／Ta值介于1．61～1．80，且土壤容重大，Ts／Ta值也大，三种农业土壤的Ts／Ta平均值可取1．68。用烘干至饱和含水量的砂质壤土和壤上的土柱试验结果表明，选用不同的Ts／Ta值，引起的含水量偏差分别为0．001～－0．005cm3／cm3和0．007～0．006cm3／cm3。对于砂质壤土，在实际合水量不变但改变土壤温度的情况下，TDR测定的含水量在实际含水量大于0．30cm3／cm3时有明显的偏差，且温度升高，TDR测定的含水量偏低，反之亦然。本文还给出了温度每增加（或减少）1℃引起的含水量测定值的偏差范围以及进行修正的方法。
Semi-theoretical and semi-empirical calibration curve θv = (T / Ta-Ts / Ta) / (Kw0.) Of soil water content (θv) and propagation time (T) of electromagnetic waves in time domain reflectometer (TDR) 5-1) Usually used to calculate soil moisture content. In this experiment, the T / T values of dried soils with different textures and different bulk density were measured by TDR. The results showed that the Ts / Ta values of the four tested soils ranged from 1.61 to 1.80, the soil bulk density was large, and the Ts / Ta values were also large. The average values of Ts / Ta for the three kinds of agricultural soils were 1.68. The result of soil column test on sandy loam and soil with saturated water content shows that the variation of water content caused by different Ts / Ta values is 0.001-0.005cm3 / cm3 and 0.007 ~ 0.006 cm3 / cm3. For sandy loam, the water content measured by TDR is obviously deviated when the actual water content is greater than 0.30cm3 / cm3 under the condition that the actual water content is the same but the soil temperature is changed, and the temperature increases and the water content measured by TDR Low, and vice versa. This article also gives the deviation of the measured value of the water content caused by each increase (or decrease) in the temperature by 1 ° C and the method of correction.