Essays in Applied Pedology: III-Bukoba: High and Low Fertility on a Laterised Soil and including a Note on Soil Fertility at Nyakato

Abstract

Bukoba is a small township and lake port in Tanganyika Territory, on the west coast of the Victoria Nyanza, twenty-eight miles south of the point of entry of one of the principal Nile Head-Waters, the Kagera River. The name is also that of an administrative district, which lies between the Uganda border on the north and Biharamulo District on the south and runs west to the Belgian mandated territory of Ruanda, adjoining it along the middle course of the Kagera. Bukoba District thus includes in its western half the long low-lying valley of the Mwisha River and the highland of Karagwe. The easternmost part of the district is however the part with which the present essay is mainly concerned: a strip of humid ridge-and-valley country twelve to sixteen miles wide running down the lake coast from latitude 1 S. to 2 S., ie for about seventy. miles. This area of about a thousand square miles, comparable in size with one of the smaller English counties, contains 230,000 rural inhabitants. The only townfolk, those in Bukoba itself, number less than 2,000. The density of population reaches 1,230 per square mile in one of the sub-chiefdoms. In five others it exceeds 400 and over the remainder of the area it averages 180. Thus, in the most crowded parts each family, reckoned at five persons, is supported by only 2.6 acres, and in the least crowded parts by 17.8 acres on the average. For East Africa such figures represent very close settlement. The people are the Bahaya, bananaeaters and to a limited extent cattlekeepers. They live in family units on permanent heritable holdings, each house and attached quarters for cattle standing hidden in its banana-grove. A group of adjoining holdings is marked as a feature in the landscape by its aggregate stand of bananas, sharply limited against surrounding larger stretches of unenclosed treeless grassland. These banana-grove" villages" may partly fill a valley alongside a stream, or may form the skyline on a high ridge, or may occupy middle positions on slopes, with open. ground above and below. The intervening lands are mostly grazing commons, but patches of them are tilled. Many of the ridges' end in sandstone bluffs and scree: slopes, and these outcrops of rock render a proportion of the land agriculturally untenable. The main river-valleys and valley junctions contain considerable areas of permanent swamp, some parts of which are papyrus, some are tussocky grassland on peat, and some carry blocks of dense evergreen swamp-forest. There are small remnants of rain-forest on the steep sides of certain ridges.