QUANTITATIVE RELATIONSHIPS BETWEEN SOIL COLOR AND HEMATITE CONTENT

We determined that the degree of redness of soils from Europe and Brazil, as given by redness ratings based on visual or spectrophotometric color measurements, was highly correlated with hematite content. For the European soils (mostly Alfisols) the pigmenting power of hematite was higher than for Brazilian soils (Oxisols and Ultisols). This suggests that, for predictive purposes, different calibration lines should be used for different groups of soils. In spite of this general limitation, color appears to be a useful tool to predict approximately the hematite content of soils.