Bush-control studies in the drier areas of Kenya. 2. An evaluation of the Holt IXa 'Bush Breaker' in Tarchonanthus/Acacia thicket.

Published online
06 Mar 1966
Content type
Journal article
Journal title
Journal of Applied Ecology
DOI
10.2307/2401667

Author(s)
Pratt, D. J.

Publication language
English
Location
Africa South of Sahara & Kenya

Abstract

In experiments begun in 1958 in Baringo District Kenya, the Holt IXa bush control machine was used ± grass sowing and subsequent burning in a grazing area rendered unproductive by Tarchonanthus/Acacia thicket. The treatments were combined factorially. Apart from a transient decrease 'in numbers of seedling trees the Holt machine did not kill any of the established bush species. Tarchonan-thus spp. were generally unaffected by the treatments. A. brevispica and Dichrostachys cinerea became more numerous after the Holt treatment and were checked only by sowing and burning respectively. There was no advantage in using the machine in 2 successive years and A. seyal and A. nilotica tended to increase on plots where it had been used twice or not at all. Notwithstanding the rapid regeneration of the woody species, especially T. camphoratus and A. brevispica, the Holt machine reduced the bush cover to a more manageable level and left a seedbed.
It was essential to sow grass in the soil corrugations left by the machine both to compete with the seedling trees and to provide sufficient material to promote an effective fire later. A nucleus of sown grasses particularly Rhodes grass (Chloris gayana) was established by the end of the season. Treatments generally improved the grass cover. A single burning checked the regeneration of the woody species and significantly decreased the frequency of the undesirable native perennial Harpachne schimperi without affecting the frequency of the sown species. It is estimated that the sequence of Holt treatment, sowing and burning increased the yield of grass at least six-fold within 3 years and also made the area more accessible for grazing. The cost of the work was approximately 40 E.A. Shs (East African shillings) per ac.-M.Y.

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