近赤外反射光分光法による土壌水分の定量分析

抄録

A near-infrared reflectance spectrophotometer with optical fiber was developed to determine soil moisture content in soil layer. The major components of the measurement system were a halogen lamp, a feed and return fiber optic cable, a spectrophtometer, and a personal computer as a system controller. Light was induced in a feed optical fiber to soil surface and reflect ray was also induced in a return optical fiber to spectro-photometer. The percent refrectances of soil surface at 1.94 /zm wavelength were correlated with the soil moisture contents. However, soil particle size deviation affects the percent reflectance. To remove this influence, a reflectance ratio (reflectance at 1.7zim/l.9/zm) was adopted as dependent varia-ble of moisture content instead of percent reflectance. The reflectance ratio was not affected by soil temperature range 10 to 50 °C and salt concentration of soil solution. Reflectance ratio vs. soilmoisture content curves were best fit for exponential curve. Furthermore, each soil appears to have a unique moisture-reflectance curve. It was concluded that this technique of soil moisture measurement is feasible and deserved further research.