Evaluation and Comparison of DTPA Extractanting Methods for Available Cationic Micronutrients in Non-acidic Soils of Andhra Pradesh, India

The research work was carried out to compare and evaluate the extractability of cationic micronutrients (Zn, Cu, Fe and Mn) using widely employed diethylene triamine pentaacetic acid (DTPA)-triethanolamine (TEA)-CaCl₂ method with that of multinutrient extractant (ammonium bicarbonate (AB)-DTPA) in Inceptisols, Alfisols and Entisols in the erstwhile united Andhra Pradesh. The percent variation of extraction of Zn was higher in soils with DTPA-TEA-CaCl₂ over AB-DTPA method in all the soil orders (types) in the range of 35.3% to 46.2%. AB-DTPA extracted high amounts of Cu to an extent of 10%-21% in Entisols and Alfisls, respectively. In Inceptisols both extracatants extracted equal amounts of Cu. AB-DTPA extracted high amounts of Fe 13% and 18% in Alfisols and Entisols compared to that of DTPA-TEA-CaCl₂ method and DTPA-TEA-CaCl₂ method was good extract for Fe in Inceptisols and even for Mn in Alfisols. The amounts of micronutrient contents extracted were found to be highly and significantly correlated with soil properties like electrical conductivity (EC) and organic carbon (OC). The individual micronutrient contents of Zn, Cu and Fe extracted by DTPA-TEA-CaCl₂ methods were found to be highly correlated with that of AB-DTPA extractant. However, such correlation was not observed for Mn extraction when all soils were grouped.