Survey of the fertility status of soils under `cerrado" vegetation in Brazil

THE SOILS TYPICALLY HAVE A PH OF 4.8 TO 5.2, PERCENTAGE OF ORGANIC MATTER OF 1.5 TO 3.0, AND EXTREMELY LOW VALUES OF EFFECTIVE CEC AND EXTRACTABLE CALCIUM, MAGNESIUM, PHOSPHORUS, ZINC, AND COPPER. THEY HAD A HIGH DEGREE OF ALUMINUM SATURATION, IRON, AND MANGANESE, AND A BROAD RANGE OF TEXTURES. THE PRODUCTIVITY OF THE SOILS WAS ESTIMATED FROM THE NATURAL VEGETATION AT THE SAMPLE SITES. A POSITIVE CORRELATION WAS FOUND BETWEEN THE AMOUNT OF VEGETATION, AND IN ORDER OF IMPORTANCE, THE FOLLOWING: ZINC, MAGNESIUM, EFFECTIVE CEC, CALCIUM, PH, PHOSPHORUS, POTASSIUM, COPPER, CHROMA, AND LEVEL OF ORGANIC MATTER. RESULTS SHOWED THREE GROUPS OF VARIABLES TO BE IMPORTANT: (1) CHEMICAL VARIABLES (PHOSPHORUS, ZINC, AND MAGNESIUM); (2) TEXTURE VARIABLES (SILT/CLAY AND SAND RATIO); AND (3) COLOR VARIABLES (HUE AND CHROMA). THE RATIO OF SILT TO CLAY WAS NOT POSITIVELY RELATED TO THE AMOUNT OF VEGETATION.