LIME REQUIREMENT DETERMINATION OF TROPICAL PEAT SOIL USING BUFFER-PH METHODS

A study was conducted to calibrate and evaluate five buffers for the lime requirement (LR) determination of tropical peat soil. The buffers tested were the Shoemaker-McLean-Pratt (SMP); Mehlich; 0.1M ammonium acetate (NH4OAc); 0.1M barium acetate [(Ba(OAc)2]; and 0.1M calcium acetate [Ca(OAc)2]. Calibration was done by comparing the precision of linear regression equations adjusted to the relationships between the LR rates required to achieve pH 5.0 measured in a 1:4 (soil:water) ratio as determined by incubation and soil-buffer pH values. Incubation LR using calcium carbonate (CaCO3) to achieve pH 5.0 by peat soil was utilized to calibrate each buffer. Evaluation was carried out by assessing the LR from the calibrated buffers which estimate the LR nearest to the target pH of 5.0. The calibration study showed that the SMP and Mehlich buffers were less precise than the Ba(OAc)2, NH4OAc, and Ca(OAc)2 buffers. The evaluation study indicated that the Ba(OAC)2 buffer is the most accurate, followed by NH4OAc and Ca(OAC)2 buffers. The Ba(OAc)2 buffer method is recommended for LR determination of tropical peat soil and NH4OAc or Ca(OAC)2 as an alternative method.