Evaluation of Mehlich 3 and Ammonium Bicarbonate-DTPA Extractants for Prediction of Available Zinc in Calcareous Soils in Central Thailand

Abstract

This study was conducted in order to evaluate the efficiency of Mehlich 3 and ammonium bicarbonate-DTPA (AB-DTPA) extractants for predicting available zinc (Zn) in calcareous soils in the central part of Thailand. The relationships between the amounts of Zn extracted by Mehlich 3 and ABDTPA with those extracted by DTPA (the conventional extraction method widely used in soil testing laboratories in Thailand) and those taken up by corn were elucidated. The results showed that the amount of Zn extracted by both Mehlich 3 and AB-DTPA was significantly correlated with that extracted by DTPA (r = 0.951** and r = 0.950**, respectively) and that absorbed by corn (r = 0.954** and r = 0.925**, respectively). Moreover, the coefficient of determination (r²) for the relationship between amounts of Zn taken up by corn and extracted by the three extractants was 0.845 (DTPA), 0.855 (ABDTPA) and 0.910 (Mehlich 3). Accordingly, Mehlich 3 and AB-DTPA could be used effectively for estimating Zn availability in calcareous soils in central Thailand. However, Mehlich 3 was superior to AB-DTPA.