| 摘要: |
| 【目的】检验温度、水分、盐分三参数传感器（SMEC 300）测定土壤含水率、电导率的精度。【方法】在天津农学院西校区农田水循环试验基地进行了土壤含水率与电导率的率定试验。试验设置3种供水水平（2.65、3.25、3.80 kg）和4种盐分水平（加盐量0、20、70、100 g）以及6种矿化度梯度（1、5、10、15、20、25 g/L）。布置6个盆，每盆内干土质量为8.85 kg，土层厚度为10 cm，传感器埋置于土面下5 cm处，试验期间定期称取盆的质量，由此测得土壤实际含水率；电导率率定试验也布置6个盆，盆内加水8 L/盆，盆内放置4个传感器，每40 min测试1个处理，利用数据采集仪获取传感器数据。分别对土壤含水率和电导率进行率定。【结果】传感器测定的电导率与矿化度呈显著的指数关系，相关系数均在0.92以上；土壤盐分影响土壤含水率的率定，实际含水率与传感器测定的土壤含水率和电导率呈二元线性关系，相关系数最大为0.940 4，最小为0.601 9，均达到了显著或极显著水平，不同传感器的率定参数有较大差异。【结论】电容式土壤温度、水分、盐分三参数传感器有其对应的参数，应逐个传感器进行率定。 |
| 关键词: 土壤；含水率；电导率；传感器 |
| DOI：10.13522/j.cnki.ggps.2019179 |
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| Calibrating Soil Temperature, Water and Salt Measured Using Capacitive Sensor |
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YAO Li, WANG Yangren*, WANG Hao, LI Yonglin, FAN Xinrui
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College of Water Conservancy Engineering, Tianjin Agricultural University, Tianjin 300384, China
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| Abstract: |
| 【Background】Soil water content is important for irrigation and is a parameter for designing automatic irrigation. Traditional method for measuring soil moisture content is soil drying. Although accurate, it was tedious and laborious, unable to provide real-time soil moisture measurement. As a result, numerous alternative methods have been proposed, including neutron probe method,γ-ray transmission method, electromagnetic wave method, electrical resistance method, capacitance method and photoelectric method. Sensors able to simultaneously measure soil moisture, soil electrical conductivity (ECa) and electrical conductivity (ECw) are essential for better managing irrigation water and monitoring and controlling soil salinity.【Objective】The purpose of this paper is to test the accuracy of a capacitive sensor (three-parameter sensor) that can concurrently measure soil moisture, as well as soil electrical conductivity and salinity. The experiment was conducted in pots each packed with 8.86 kg of dry soil 10 cm thick.【Method】The three-parameter sensor used in the experiment was the SMEC 300 model. The experiment was conducted at the water-cycling experiment station at the west campus of Tianjin Agricultural University. We tested three water levels by adding 2.65, 3.25 and 3.80 kg of water to the pots, and four salt levels by adding 0, 20, 70 and 100 to the pots. There were six salinity concentration: 1, 5, 10, 15, 20 and 25 g/L. The sensors were buried 5 cm below the soil surface. During the test the pots were regularly weighed to measure the change in soil moisture content. The electrical conductivity test was conducted in plastic pots, each filled with 8L of water with four sensors in it. Each test lasted 40 minutes. The soil moisture and electrical conductivity measured from the sensors were calibrated against the results directly measured from pot weighting and the pots filled with water only.【Result】The electrical conductivity measured by the sensor increased exponentially with salinity, and their correlation coefficient was higher than 0.92. Soil salinity affected accuracy of the soil moisture measurement and the real moisture was linearly related to soil moisture content and electrically conductivity measured by the sensor at significant level or above, with the correlation coefficient varying from 0.601 9 to 0.940 4. It also found that the calibration parameters varied with individual sensors.【Conclusion】 Calibration parameters of the capacitive sensors are not unique, and thus each sensor should be calibrated individually. Soil salinity affected accuracy of the sensors, and accuracy of the soil moisture measured by the sensor could be improved by including the electrical conductivity measured by it in the calibration. |
| Key words: soil; moisture content; electrical conductivity; capacitive sensor |
