(ii) The rooting problem can only be attacked
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efficiently by machines which combine a vertical and a horizontal cut. This condition is met by the Davis plough, which has proved very valuable at Kongwa; and it is interesting to note that the principle is incorporated in the new Harrison-Blaw-Knox root cutter.
(b) Experiments on tree poisoning. Sodium arsenite applied in frills to miombo trees at Urambo was no more efficient in killing the aerial parts than simple frilling without arsenite, but it remains to be seen whether the under- ground parts are killed. When applied in holes bored in the trunk arsenite was less efficient than frilling. Baobabs at Kongwa were killed by arsenite placed in. holes at 18 in. intervals round the bole, the effect being that of ringing.
(c) The Chief Scientific Officer acted for a time in 1947-48 as chairman of a. committee on building priorities.
(d) The Chief Scientific Officer spent June, 1947, in the Gambia, West Africa, in connection with experiments on rice and groundnut mechanisation being con- ducted there by the Human Nutrition Research Unit, Medical Research Council..
(e) Close and friendly relations have been maintained with the East African Agricultural Research Organisation. The Soil Chemist is a member of the Organisation's committee on soil analysis. Members of the staff have visited the East African Agricultural Research Station at Amani, the Tanganyika Territory Coffee Research Station at Lyamungu, Moshi, and the East African Industrial Research Board's Laboratories at Nairobi.
(f) The Entomologist served on a committee on termite control in houses, set. up by the Civil Engineering Department.
(g) The Department established and maintained nurseries for the production of planting material of ornamental and economic trees and shrubs at Unit 1,. and later at Sagara, and plants of over 30 species were produced. Vegetable seed and planting material of tropical fruit trees were secured for the Southern Province.
(h) The Statistician prepared a report on the statistical needs of the Scheme as a whole. In particular, the statistics of labour utilisation and hospital attendances were outlined in collaboration with departmental officers. A survey showed that on any one day about 10 per cent. of the individuals in the labour force were not the persons whose work tickets they held. An exploratory study was made of the statistics of tractor performance.
PART 2. SURVEY RESULTS AND TECHNICAL DATA
The Catena at Kongwa
10. SURVEYS
The Kongwa Region is for the most part a rolling plain, with steeper slopes only in the neighbourhood of the Kiboriani and Chinene hills, which bound it to the south and west, or of the inselbergs which stand out of it at many points.. The topography is thus far more level than that of the classical home of the concept of the catena in the foothills of the Usambara mountains.
The climate of Kongwa is arid, total rainfall being 25 in. per year or below, in a single rainy season of less than six months. The country dries up com- pletely in the long dry season, principally as a result of transpiration by the Commiphora scrub, and there are no permanent watercourses, the drainage being: almost completely dead..
The rocks of the area are principally gneisses of the Basement Complex. The two types of major significance for soil formation are a pale granitic gneiss and a dark, often nearly black, hornblende gneiss. The granitic gneiss being the harder of the two types, tends to occur below, or even to outcrop at, the crests. of the gentle ridges, while the hornblende gneiss underlies the slopes.
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