48 REPORT OF CHEMICAL LABORATOKY 



In the Gezira, at Wad Medani, the rainfall is ofBcially stated to be 400 mm. (about 

 16 inches). This is slightly greater than the average in the dry farming districts in the 

 United States. Even half-way between Wad Medani and Kamlin, as reference to the map 

 on pacjes 46 and 47 will show, the rainfall is greater than that prevailing in Utah and 

 California where wheat is successfully grown. That the season of rainfall, more especially 

 in the latitude of Wad Medani and south of it, is suitable for cotton, is proved by the fact 

 that it has been extensively grown in the past, in spite of the unscientific methods practised 

 by the natives. Improvement of seed and more modern methods of cultivation would 

 appear to be all that are required to make this enterprise a financial success. 



Up to the present but little work has been done on the soils of the Sudan, and 

 especially on those of the Gezira. In 1903 a few samples collected by Sir W. Willcocks' were 

 examined by Mr. Hughes, of the Egyptian Department of Agriculture, but no mechanical 

 analyses were made, and, as Mr. Hughes was not supplied with samples of the subsoil, the 

 results, e.g. as regards soluble salts, are not only incomplete, but even misleading, further, 

 the two samples of which more complete chemical examinations were made and which are 

 described by Sir W. Willcocks as "typical Gezira soil," one collected on the Blue Nile 

 and the other on the White Nile side, were taken only 10 miles and 2 miles, respectively, 

 from Khartoum. A comparison with the results in the tables on page 54 et seq. will show- 

 that these soils are not correctly designated as typical of the Gezira generally, since the 

 soils of that district vary greatly, both their mechanical and chemical characters being 

 dependent upon the location — that is to say, upon the climatic conditions, rainfall 

 especially. 



At Khartoum, the rainfall is a little over 10 centimetres. At the southern end of the 

 Gezira, it is approximately ten times as great ; and while Sudan soils, like those of Egypt, 

 are chiefly river-borne silt of Abyssinian origin, the deposit has suffered very material 

 change in those places in which the rainfall has been more abundant. There is also 

 evidence of change as a result of the alkaline water of the W'hite Nile, some of the soils on 

 this side of the Gezira having their clay in a more puddled condition, and therefore 

 less permeable. 



The natives of the Gezira distinguish two main classes of soil. The better of these, 

 from the point of view of suitability for cultivation under ordinary conditions {i.e. rainfall 

 cultivation), is termed by them bardobe. This is the typical so-called cotton soil, 

 characterised by the deep cracks which form when the soil dries. The other chief variety 

 cracks but little, if at all, on drying. It is called azaza and is said to be uncultivable, or, 

 at best, to return inferior yields. Another variety of soil, and the one most esteemed 

 by the native, is termed fud or fuda. This appears to be merely bardobe in a good state 

 of tilth. On drying, it cracks to a less extent than does ordinary bardobe soil, and 

 remains friable and permeable. In view of the proposed irrigation of a section of the 

 Gezira a very great number of soils, with subsoils down to four feet, have been collected 

 for us by Mr. S. C. Dunn, the Government Geologist, and examined in the laboratory. 

 A sketch map prepared by Mr. Dunn, showing the points of collection, is found on page 51. 

 It is evident from the results of the mechanical analyses that while azaza soils are, 

 generally speaking, lighter than bardobe the difference in composition is not nearly so 

 great as estimated by the native. The inferior returns under present conditions are due in 

 great part to scanty rainfall. The porous nature of the soil is also a result of this same 

 condition, so that the effect of low rainfall on crop production is doubly felt. Bardobe soils, 



I The Nile in 1904, p. 100 



