SOME PROBLEMS OF RESEARCH II 



has been altered over large areas by too-frequent cultivation, partly 

 by direct pressure of population, but mostly by the introduction of 

 cash crops, which necessitate the cultivation of much larger areas. 

 An extreme case is the Owerri Province of Southern Nigeria, 

 where the agricultural population is probably denser than any- 

 where else in the continent, between 300 and 400 per square mile. 

 In this area the resting period which the soil actually receives has 

 been reduced almost to nil, with the result that the resting period 

 which would be required to restore its original fertility is very long 

 indeed. The reduction of soil fertility which results from these 

 factors is well demonstrated in Senegal, which has been given 

 over to the production of groundnuts. Here three belts can be 

 defined in terms of rainfall conditions, one in the dry land to the 

 north, the second stretching east in the latitude of Dakar, and the 

 third in the damper country surrounding the Gambia River. 

 When groundnut production first started the northern belt was 

 found the most suitable and population concentrated there. Soon 

 the soil deteriorated, and to-day practically all the export comes 

 from the middle and southern belts, whereas in a few years' time it 

 is feared that the middle belt will become much less profitable. 

 This series of events has naturally helped in the southern migration 

 of people referred to above. 



Against these factors agricultural workers are attempting every- 

 where to change the crop/ fallow proportion in the other direction 

 by establishing systems of fixed cultivation, building upon that 

 type of shifting cultivation where the population remains in the 

 same place. The methods which are being introduced involve the 

 rotation of crops, mixed cropping, green manuring, composting, 

 and especially mixed farming, all of these being designed to put 

 fertility back into the soil as fast as it is drawn out by crops. As an 

 example of the adaptability of such systems when under pressure of 

 population, we may refer to Ukara Island in Lake Victoria, where 

 a genuine system of mixed farming, of the type which agricultural 

 experts are attempting to popularize in both East and West Africa 

 by various kinds of education, has apparently been spontaneously 

 evolved. 



Many of the environmental .changes considered above affect 

 man indirectly through his stock, and therefore some of the changes 



