[Comparison of kieserite and ground magnesium limestone (GML) on FFB yield and oil to bunch content of mature oil palm]

An experiment was carried out to compare the performance of kieserite and Ground Magnesium Limestone (GML) on oil palm planted on Rengam series soil (Typic kandiudult) in Kerteh, Terengganu. The experiment commenced in March 1989 on eight-year-old DxP planting. The rates tested were 0, 0.12, 0.24, 0.36 and 0.48 kg MgO/palm/year. An additional treatment of 0.48 kg MgO/palm/3 years for GML was included to evaluate the effectiveness of less frequent application of this fertilizer. Each rate was equally split and applied twice a year together with other basal fertilizers. The experimental design was RCBD with three replicates. The plot size was 5 x 5 palms with the central nine as recording palms. Results over an eight-year period (1990-1997) showed no significant difference between GML and kieserite on the fresh fruit bunch (FFB) yield. However, overall kieserite has a slight edge over GML. The best kieserite treatment was 0.24 kg MgO/palm/year that produced 8.7 per cent FFB yield improvement over the control. The best GML treatment was 0.48 kg MgO/palm/year, the highest rate tested, which gave a 6.0 per cent FFB yield improvement over the control. At their respective best rates, kieserite resulted in 2.5 per cent higher yield than GML although this was not significantly different. Application of GML at 0.48 kg MgO/palm every three years did not improve FFB yield but resulted in significantly lower FFB yield compared with that of annual application. There was no significant different in bunch number and bunch weight arising from the usage of the two fertilizers. Results over five years (1993-1997) showed that application of kieserite up to 0.24 kg MgO/palm/year improved oil to bunch content. At this rate there was a 3.1 per cent improvement in oil to bunch content over that of the control. However, higher rates of MgO were found to depress oil to bunch content. By using the response curve method, the optimum MgO rate for optimum oil to bunch content was found to be at 0.7 kg kieserite/palm/year. Kieserite application at 0.24 kg MgO/palm/year also gave the highest kernel to bunch ratio and it also gave a 7.6 per cent improvement over that of the control.