報文

近赤外分光法を用いた土壌診断手法の開発
−偏光を利用した手法の検討−

Development of Soil Diagnosis Technique Using Near-Infrared Spectroscopy
− Applicability of Technique Using Polarized Light −

梅田 大樹・澁澤 　栄・高�� 正夫・岡山 　毅・平子 進一
Hiroki UMEDA, Sakae SHIBUSAWA, Masao TAKAYANAGI, Tsuyoshi OKAYAMA, and Shinichi HIRAKO

A new technique applying polarized near-infrared spectroscopy is proposed for precise measurements of moisture content in soil. Diffuse reflectance spectra of seven kinds of soil samples were measured. Linear relation between the moisture content and the signal intensity due to water is lost when the moisture content of the soil is high, presumably because intense direct reflection at the sample surface interferes measurements. Application of polarized light was found to improve the precision of quantitative measurement. In the scheme, by using a polarizing plate for each of the incident and reflected light, p-polarized light was irradiated on a soil sample, while only the s-polarized light from the sample was detected. The technique is expected to be applicable not only for precise measurements of moisture content but also for diagnosis of texture of soil with high concentration moisture.

Keywords:Near-infrared spectroscopy, soil physics, soil condition, moisture content, polarized measurements