Factors Affecting the Distribution and Availability of Micronutrient Elements in Major Soil Groups of Rajasthan—I. Surface Soils

The nature of parent material and the degree of weathering have a bearing on the total micronutrient elements status of the soils of Rajasthan, whereas, pH, organic matter, soil texture, calcium carbonate and type of clay mineral markedly control the availability of micronutrient elements in the soils. The contents of micronutrient elements (Mn, Fe, Cu, Zn, B and Mo) in the ten major soils of Rajasthan are influenced by the type of soil parent material and the extent of weathering. Relatively less weathered desert soils formed from aeolian deposits of fine sands contain low amounts of total manganese, iron, copper and boron, but fairly high amount of zinc. Old alluvial soil formed from alluvium-arenaceous materials contains the lowest amounts of all the micronutrient elements except boron. Relatively more weathered gray brown, red foot-hill, yellowish brown and black soils derived from various sedimentary alluviums have high contents of Mn, Fe, Cu and B. Except in calcareous (gray brown and deep black) soils, zinc content becomes lower as the soils are more weathered. Levels of micronutrient elements in different soils of Rajasthan, their deficiency or sufficiency, are discussed.