RADIOMETRIC EVALUATION OF SOME SOIL PROPERTIES

Abstract

The radiation reflected from the ground can rarely be measured over the whole of the region as such field sampling is essential. Sample sites may be taken as representative. The radiation is spatially correlated and largely stochastic. Soil properties (numerical values) may be obtained from analysis of influence pattern of EMR (Electro Magnetic Radiation). In this study, radiometric analysis (0.4 pm to 1.0 pm wavelength) was carried out for evaluating some soil properties viz, grain size, moisture content, soil density and permeability. Ground acquisition of soil samples was made concurrently with radiometric measurements, in the month of December, 1990; and June 1991. The results obtained shows that the spectral radiance increases as moisture decreases, but in case of silt having less percentage of the organic content and clay, the spectral radiance increases as moisture contents increases upto a certain limit and after that it is vice-versa. In case of sand devoid of organic matter, the effect of the moisture content is not dominant. The relationship between density and refletance is nearly parabolic, probably this is due to the variation in texture texture and composition of the soil. In case of sand the effect of density on the reflectance is negiligible. In a similar way the reflectance was correlated with mean grain size at wavelength 0.504Am and 1.0 Mm giving the better (iv) results. For claye soils the reflectance increases slightly with mean grain size. For sand and silty soil the reflectance increases with decrease in mean grain size. The soil permeability has been assessed through its dependency on grain size statistics. The study has clearly shown that the numerical values of soil properties may be evaluated from radiometric data analysis. However to have a proper methodology extensive modelling is essential.