Bush-control studies in the drier areas of Kenya. 2. An evaluation of the Holt IXa "bush breaker" in Tarchonanthus/ Acacia thicket.
Effects were studied of machine-clearing of mature Tarchonanthus/Acacia thicket factorially combined with sowing 2.5 lb/ac of a seeds mixture mainly consisting of Chloris gayana/Eragrostis superba, and subsequent burning. The machine did not kill any of the species studied. Regrowth was particularly rapid in T. camphoratus and A. brevispica after machine-clearing, and their thicket habit was accentuated; because of this and the increase in numbers of tree seedlings it was essential to sow grass in the soil corrugations left by the machine. Where sufficient grass accumulated, burning was wholly beneficial. There was no advantage in using the machine in 2 successive years. Treatments generally improved the grass cover. Burning significantly decreased the frequency of Harpachne schimperi, a dominant of the natural flora, without affecting C. gayana. Machine-clearing followed by sowing and burning was estimated to have given a 6-fold increase in grass productivity. -R.B.