Silviculture, growth and yield of neem (Azadirachta indica A. Juss.) plantations in northern Ghana

Abstract

The silviculture and growth and yield of neem (Azadirachta indica A. Juss.) grown in individual and community plantations in the Tamale Forest District of Northern Ghana was investigated in 1995. Owing to rising populations and an increasing demand for agricultural land, shortages of wood for poles, rafters and fuel are increasing. Plantations of neem and other exotic species were rapidly expanded from 1989 to minimize the effect of the forthcoming shortage and to guarantee wood products for village communities. The current silviculture for neem in Northern Ghana is adequate for present levels of plantation establishment but will have to improve as the area planted expands. The principal changes will be seed collection from superior phenotypes, improvement in nursery and outplanting practice, closer initial spacing, and thinning . The measurement o f 120 temporary sample plots in 30 plantations varying in age from one to nine years in the Tamale Forest District provided the data for the construction of local and standard volume table equations and the development of an empirical yield table. The Yield Table showed that the mean annual increment o f Site Class I, II and in neem plantations was 12.9, 8.1 and 4.3 m3/ha on biologically optimum rotations of 5, 7 and 11 years respectively. The three-parameter Weibull probability density function, the Normal and the Log-normal distributions were used to fit the diameter distributions of the neem plantations. Comparisons of the observed and predicted diameter frequencies indicate that the Log-normal distribution gave the best description of the diameter distributions, though the Weibull function was also found to be suitable.