EVALUATION OF TWO BUFFERING METHODS FOR ESTIMATING SOIL BUFFERING CAPACITY AND LIME REQUIREMENT IN AN OIL PALM PLANTATION

ABSTRACT
Buffering capacity is defined as the soil’s capacity to maintain a relatively stable pH despite the presence of acidifying or alkalizing factors. To adjust the pH to a desired level, determining the lime requirement is required. Liming requirements refer to the amount of lime needed to adjust soil pH to optimal levels for plant growth. Lime is used to increase soil pH, particularly when it drops below critical thresholds that can negatively impact crop yield. The study aimed at evaluating two buffering methods for estimating soil buffering capacity and lime requirement in an oil palm plantation.
The study was conducted on soil samples collected at 0-15cm and 15-30 cm soil depths. The samples were analyzed for some physical and chemical properties using standard method. The shoemaker method determined by equilibrating 10g soil with 20 ml Shoemaker buffer solution. The suspension was shaken at 160 revolutions per minute for 10 minutes. The Ca(OH)2 method was determined by adding 25 ml of 0.01 M CaCl2 to the weighed 5 g soil duplicate followed by treating with increasing amounts (0 ml, 1 ml, 1.5 ml 2 ml, 2.5 ml, 3 ml) of 0.022M Ca(OH)2 and the pH of the Ca(OH)2 soil suspension was determined after shaking for 1 hour and a buffer curve (pH versus tonCaCO3ha-1) was constructed to access the impact of the various volumes of 0.022M Ca(OH)2 on the pH of the soil solution.
The results of the physical and chemical properties analyzed showed a Loamy sand and Sandy loam textural class with a very strongly acidic pH (4.69). The OC, TON and Av.P had mean values of 8.8, 0.43 and 3.06 respectively. The CEC, ECEC and BS (%) had mean values of 1.56 cmolkg-1, 2.85 cmolkg-1 and 53.05% respectively. The lime requirement showed that the Ca(OH)2 had a better mean value of 5.33 tonCaCO3ha-1 compared to the Shoemaker equilibration method which gave a mean value of 5.28 tonCaCO3ha-1. The soil buffering capacity considering the Ca(OH)2 titration method was 2.80 and 2.72 tonCaCO3ha-1 for 0-15 and 15-30 cm soil depths respectively. The results also showed that the recommended LR equation at 0-15 and 15-30 cm soil depth is given as: pH = 0.363(LR) + 4.666 and pH = 0.368(LR) + 4.403 respectively considering the Ca(OH)2 titration method. The Ca(OH)2 method did not involve hazardous chemicals, it was easier to handle and gave the estimates that were not significantly different from the Shoemaker method as a result, it is advisable and recommended that farmers should adopt the Ca(OH)2 method.