The effect of the number of graftings and pollarding height on the yield of rehabilitated cocoa

A field experiment was conducted in a smallholder cocoa holding at Kampong Ranggu Sabah in 1998-2004. The experiment was laid out in a 2x4 factorial with randomized complete block design in which the combining treatments comprised of pollarding heights of 1.524 m (5 feet) and 2.134m (7 feet) and graftings at 1,2,3 and 4 graftings per plant. The objective of this study is to determine the suitable pollarding height and the optimum number of graftings for high yields in the rehabilitated cocoa. Mature cocoa trees of 18 years old were grafted by side grafting technique according to the treatments of the number of graftings and the pollarding height of stock trees. The results of the study showed that the yield of rehabilitated cocoa was significantly affected by both the number of graftings and the pollarding height of stock trees. Rehabilitated cocoa with the stock trees pollarded at 2.314 (7 feet) produced significantly higher yield than those trees pollarded at 1.524m (5 feet) for 6 consecutive years from 1999 to 2004. For 6 years, crop yields of 1,369 kg/ha/year and 1,637 kg/ha/year were achieved with trees pollarded at 1.524 m and at 2.314 m, respectively. This significant effect may be attributed to the better availability of reserved nutrients in the longer main trunk which is able to supply nutrient to the scions or due to the efficiency in nutrient uptake by the longer height of the main trunk. The finding suggested that pollarding of stock trees at the height of 2.134 m (7 feet) was also showed that cocoa trees grafted with more than one grafting per tree exhibited significantly higher yields as compared to those rehabilitated trees with one grafting per tree. For 6 consecutive years crop yields with an annual average yield of 1,122 kg/ha/year, 1,434 kg/ha/year, 1,778 kg/ha/year and 1,776 kg/ha/year were achieved with trees grafted with 1 grafting, 2 grafting, 3 grafting and 4 grafting per tree respectivel y. The results suggested that early achievable high yields would help the farmer to compensate for the loss of yield from the mother trees by grafting at least 2,3, and 4 graftings per tree during the rehabilitation period. In view of ease in the crop management, we suggested that 2 to 3 graftings per tree would be the optimum number of graftings so as to adapt to the current cocoa planting density, which is at 800-1,333 trees per ha. Moreover, canopy pruning would not be a tedious and difficult work at the later stages with 2 graftings per tree.