Evaluation of laboratory indices of magnesium availability

Abstract

A study was conducted to evolve a suitable extractant of available Mg in soil. Twenty soils were selected for the study assuring wide variation in their properties in relation to Mg availability. The various extractants in the final screening showed the following decreasing order in their efficiency for extracting Mg; 0.005 M DTPA + 0.005 M CaCI2 .Mathew's triacid > 0.1 M acetic acid + 0.04 M Ca lactate > Keith's reagent > 0.0125 M CaCI,, 1 N NH4OAc > 0.05 M HCI > 0.005 M DTPA. The amount of Mg extracted by various extractants failed to correlate significantly with the Mg uptake of test crop (rice) as well as the per cent of Mg in the crop. The performance of 0.05 M HCI was promising with respect to the pattern of release, degree of variability due to varying periods of equilibration ami the magnitude of Mg extracted at the optimum period of equilibration.