CAB129-37 — Page 142

(g) Levelling

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A levelling operation was desirable before light-wheeled tractors were put to work. A leveller, made locally by the Corporation, met this need very efficiently. It is constructed of heavy material, such as rails, in the shape of a rectangle, with diagonal ties of the same material; 6 in.-8 in. steel pegs in sleeves welded to the frame help to pick up any root trash still left. These levellers can be used in pairs dragged behind a heavy crawler tractor.

The leveller can be used effectively only during the dry months.

Other Regions

74. Materially the same land-clearing operations are necessary at Urambo and in the Southern Province.

Improvements in Technique

75. Much has had to be learned about the technique of bush clearing and the Corporation has concentrated the work of its Operational Research Unit on this problem.

76. The original White Paper estimate of the cost of clearing per acre was £3 17s. 4d.; in the first year the comparable cost of clearing an acre was calculated as being ten times this figure. Much of the difference was due to the tasks proving more difficult than was anticipated. Other reasons for the disparity were the lack of experience in African bush clearing; the unserviceable condition of the heavy tractors; the lack of proper equipment to deal with the peculiar root system at Kongwa; wind- rowing flattened bush when green and so bulldozing an excessive quantity of soil into the windrows, and root ripping in the height of the dry season, with resultant wear and tear on moving parts.

77. One great economy has been effected by the introduction of chain cable clearing. This system had originally been tested by the Managing Agents and the Contractors and rejected. It was again tried experimentally, at Urambo, in January, 1949. This time it was adopted for use in all areas and the technique was improved at Kongwa. A heavy 3 in. chain cable is attached to two heavy tractors which move through the bush 20-30 feet apart. A third tractor ("the scrum half" as it has been named) follows to deal with particularly stout trees which the chain cable cannot pull out of the ground. The use of the chain cable greatly increases the area of bush which can be flattened in a day.

78. The degree of improvement in efficiency and rate of pulling the vegetation out by the roots was so encouraging in the Isoberlinia- Brachystegia-Other Species Woodland at Urambo-under suitable conditions of soil moisture to a depth of two to four feet-that an early trial was organised in the Deciduous Thicket at Kongwa, again with considerable success. Owing to the differences in soil, in soil-moisture and in growth- form of aerial and root portions of the thicket vegetation, the results achievable were shown to be less satisfactory than those at Urambo. Towards the end of the period under report preliminary trials of the method were made at Nachingwea, Southern Province, with promising indications for the future.

79. This improved method of flattening undoubtedly was the outstanding achievement of the past year and holds great promise for future work in the clearing agrevegetatibi.097

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