提高中子浅层测湿精度率定方法的比较研究

Study on the Different Methods of Calibrating Shallow Soil Moisture Content Measured with Neutron Instrument

为了提高中子仪浅层测湿精度率定方程的建立,以烘干法为比较基准,进行了大田标定及验证试验。结果表明,分层分段法在整个浅层率定过程中表现最优;由深层率定方程推求浅层土壤含水率的间接推导法不能改善整个浅层土壤中子测湿精度;由非线性最小二乘法拟合双曲线方程作为整个土壤浅层率定模型的实际应用效果不稳定,试验误差较大。

Neutron instrument is a high-tech, intelligent and advanced instrument, it is extensively used in measuring soil moisture content without disturbing soll in fieldwork, can be easily operated to successively monitor soil moisture content at any depths at the same measuring site, the measurement does not be limited by seasons, change of physical and chemical properties of soils, and can be connected with automatically recording system and computer. Neutron instrument is extensively used in many domains, such as pedology, geography, agriculture, forestry, meteorology, hydrogeology, and water conservancy and building projects. In this paper, the calibrating equation of soil moisture content measured with neutron instrument is developed, and the methods for increasing the measuring precision of shallow soil moisture content are researched, compared and verified. The traditional dying method is regarded as the criterion in measuring soil moisture content. The test results are calibrated and verified in field. The result shows that the hlerarchlcal-section method is optimal in calibrating shallow soil moisture, and the relative errors are lower than 10%, which can satisfy the requirements of measuring shallow soll moisture content; the measuring precision of shallow soll moisture content can not be increased by the indirect derivation using deep soil moisture content; the results of shallow soll moisture content calibrated with the regressed equation of nonlinear least square method are not stable, and the test errors are high. Generally, it is considered that the detecting radius of neutron instrument is related to soil properties and moisture content.