Proceedings of the South & East African combined agricultural, cotton, entomological and mycological conference held at Nairobi, August, 1926

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Monograph

Identifikator:: 1738588467

URN:: urn:nbn:de:zbw-retromon-115043

Document type:: Monograph

Title:: Proceedings of the South & East African combined agricultural, cotton, entomological and mycological conference held at Nairobi, August, 1926

Place of publication:: Nairobi

Publisher:: East African Standard

Year of publication:: 1926

Scope:: VI, 337 Seiten; Ill.

Digitisation:: 2020

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Agriculture

Collection:: Economics Books

PART II. ol lavas. These soils have a high clay content, but so wonderful is their crumb structure that they work like medium loams. Their original vegetation was forest but much has been cleared. Most of the coffee plantations are on this type of soil. The Naivashan lavas in all probability give rise to much of the soil of the Trans-Nzoia. Unfortunately little is known of the geology of this area, but if Professor Gregory is correct in his estimate of the age of Mount Elgon, there can be no doubt but that much of this area is derived from this series. Little can be said regarding the soils of the Trans-Nzoia. During the Pleistocene period the volcanoes of Longonot, Suswa, and Menengai, among others, were active. Ash and scorie from them covered the soils then in existence. In parts, this is especially marked on the upper slopes of Menengai and in the Kedong Valley, the particles of ash remain unchanged. Tower down the slopes of Menengai the character of the soil changes considerably. The fresh scorize disappear, the soil becomes more clayey and possesses a certain structure absent from the soil above. These modifications are probably due to admixture with the Nyassan series and the action of water weathering some of the finer ash particles to a colloidal condition. The vegetal relationships on the soils in this area are most interesting. The mechanical composition of these soils has been considerably influenced by climatic conditions. In the more arid regions the original particles are hardly affected and the humus content of the soil is low. Where moister conditions have obtained, weathering changes have proceeded far with the formation of inorganic colloids, besides there has been a tendency for humus to collect. The soils of the drier parts are thus liable to pass into the single grain condition very readily under cultivation, where similarily derived soils containing more humus and fine fractions would retain their crumb structure longer. There is a general idea that voleanic soils are extremely rich in all plant nutrients and that all the farmer has to do is to till the soil and plant his seed when wonderful crops will be returned indefinitely. It being being known that the soils of the Kenya Highlands are volcanic in origin, this idea had a great deal to do with the origin of the pernicious system of single crop farming practised, in which the farmer has képt his soil under the same crop continuously without the addition of any manure whatsoever. If it had been possible, not even the bare fallowing, that the climate has necessitated, would have been allowed. It has been noticed by some farmers, that the drop in crop production cannot be ascribed solely to the African scape-goat— decreasing rainfall. There was, they concluded. a lack of plant nutrients; manuring has followed. The soils of Kenya, in common with the majority of African soils, are, on the whole, deficient in phosphates. Although it has not been possible, until recently, to conduct any manurial experiments, the use of phosphates has been widely recommended. Whereever such manuring has been practised good results have followed, but, so far, no reliable figures have been available. Nitrogen deficiency has been indicated in certain parts and crops have responded to dressings of nitrogenous manure. These deficiencies of nutrients are easily rectified. The deterioration in physical condition, that the farming practices in Kenya have, and are, causing will give more difficulty. 33

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