384 SCIENCE IN AFRICA 



by the agricultural department (Lynn 1937). In this isolated com- 

 munity a primitive system of fixed agriculture prevails. The best 

 soils are around the villages and are manured with cattle manure 

 and the primitive habits of sanitation; lands farther distant are 

 recognized as being less fertile and consequently receive less atten- 

 tion. In the opinion of the agricultural officers, conditions are ripe 

 for the introduction of a more intensive system of mixed farming; 

 experiments have been undertaken with rotations, cultivation, 

 manuring, root crops, and so on, in this locality rather than at 

 Tamale, where conditions are different. 



In Sierra Leone, except for the wetland rice areas [see Chapter 

 XII, p. 343) the general method of native agriculture consists in 

 cutting temporary clearings in forest growth, from which crops are 

 taken for one or sometimes two years. These crops usually consist 

 of rice with a small proportion of guinea corn and millet. Some- 

 times a small admixture of perennial cotton is sown, and cassava 

 may also be planted. As the cotton gives no crop in the first season, 

 and as no cultivation is given except the preparatory hoeing when 

 seed is sown, it has to compete with weeds and secondary forest 

 growth (Sampson 1930). The maintenance of fertility by bush 

 regeneration requires from eight to ten years, but the demand for 

 land leads to a lessened period of bush fallow and consequently to 

 decreased fertility, to which erosion, in a country of so heavy and 

 concentrated a rainfall, also contributes. The problem confronting 

 the agricultural department is to substitute some other method of 

 maintaining or increasing fertility. In the absence of animal hus- 

 bandry some form of green manuring appears to be required. 

 Experiments at Njala have shown Calopogonium mucunoides to be 

 best, but in view of the difficulty of inducing natives to grow green 

 manure crops which provide food for neither man nor beast, 

 experiments with pigeon peas and Centrosema puhescens are being- 

 made (Sierra Leone 1936, D.R.). Possible crop rotations and 

 methods of maintaining fertility are discussed by Sampson (1930). 



In Eastern Africa similar work is progressing. For example, in 

 Nyasaland it has been shown at the experimental station at 

 Zomba that land which is typical of large areas can be kept per- 

 manently fertile by means of suitable crop rotation combined with 

 manuring and terracing of sloping land to prevent erosion. Work 



