Effect of paclobutrazol on growth and yield of cocoa high density plantings

R. Kasran

Abstract

An experiment was carried out to study the effects of paclobutrazol, a growth retardant, on vegetative growth and yield of cocoa (Theobroma cacao L.). It was applied as a soil drenching to 1.5-year-old KKM 22 clone planted at high density (3 333 plants/ha). Six concentrations of paclobutrazol (0, 0.125, 0.250, 0.375, 0.500 and 0.625 g a.i./L) were used. Increasing the paclobutrazol concentration from 0.375 to 0.625 g a.i./L was found to reduce plant height, stem diameter, leaf size, leaf internode and leaf area index. The results also showed that increasing the paclobutrazol concentration from 0.375 to 0.625 g a.i./L increased the fraction of sky visibility from beneath the canopy. Paclobutrazol at 0.375 g a.i./L was most effective in controlling vegetative growth without any adverse effect on the plant. In this way, use of paclobutrazol would reduce pruning practices. It was also found that at this concentration, the number of bearing-flower cushions increased. While, the incidence of cherelle wilt was reduced even though cherelle set increased. It then led to a larger number of mature pods and subsequently increased yield. Highest yield was achieved up to 2.06 t dry bean yield/ha for the first year of production. Therefore, soil application of paclobutrazol at 0.375 g a.i./L was found to be suitable for controlling vegetative growth and yield improvement of 1.5-year-old KKM 22 cocoa clone at high density planting. At higher concentration of 0.625 g a.i./L, it adversely affected plant growth and pod size.

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