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 11. to be premature. Field observations which have been substantiated in some cases by trials, have indicated that there is a wide spread condition of nitrogen deficiency. Whether there is an absolute deficiency of nitrogen or a deficiency of available nitrogen only it is at present impossible to say definitely; laboratory investigation into the matter has not yet been possible; the latter explanation seems to be the more probable; 1t seems unlikely that most of the great accumulation of nitrogen in the virgin soils could have been removed in the time during which the soils have been under cultivation. It is probable that there is some factor interfering with the processes of nitrification. At the same time it has been found that the residues of leguminous crops increase the yield of cereals. For the time being the nitrogen requirements of the main crops can most economically be met by the use of leguminous green manures. If laboratory investigation elucidates this problem it will be possible for the accumulated store of nitrogen to be drawn upon. In connection with the cultivation of legumes some most unusual observations have been made. It has been mentioned above that ordinary sweet clover is a failure as a green manure crop. Sweet clover seed was inoculated with a watery suspension obtained from lucerne nodules. It has been shown elsewhere that cultures of the bacillus obtained from lucerne would strongly infect sweet clover and vice versa. The plants from the inoculated seed, here, were quite free from nodules and were only dwarf plants. Recently it has been chserved that volunteer plants of sweet clover on the plots previously sown to sweet clover were carrying a few small nodules. Tt appears that the microbe is adjusting itself to the new host plant. Similar cbservations have been made in connection with other plants. These observations open up a new line of work upon the characteristics of the nodule organism. Is the variety, that is beginning to infect the sweet clover, the same as that infecting lucerne, or is it a variety, 2ormally infecting some of the native legumes, adjusting itself to a new host plant supplying conditions not far removed from its original host? Or is there, on the other hand, some soil condition that, until the plant has adjusted itself, bestows increased immunity to infection by the requisite strain of Pseudomonas radicicola ? As soil work progresses in Kenya innumerable problems of this type, problems of high scientific interest having a direct bearing upon farming practice, will arise. Many of these are of fundamental importance and will have a bearing not only upon the type of soil but upon all the soils of that class. In addition to problems directly affecting the farmer or the farming practices there are awaiting study many soil problems, the connection of which to farming practice may not be evident but which will throw light upon a large number of partially understood phenomena. Into this category falls the relationship between the soll and the vegetation. This can only be studied properly while the true virgin vegetation still exists; changes due to cultivation would provide a corollary study. Of the various type soils only those derived from the Laikipian lavas carry true forest; the others carry grass or mixed bush and grass. The deciding factor for forest growth is not rainfall, since strips of soil derived from other formations, invading forest covered Laikipian soil, do not carry forest growth. There is some condition in the Laikipian soils that is favourable to forest orowth. It is not always present in the ILaikipian soils as is shown 36

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