PLANT INDUSTRY 405 



the roots of the crop to hold the soil. It is certainly regrettable that 

 some European-owned land in Africa is worked on a principle 

 which is not worthy to be designated as farming, but can only be 

 termed soil exploitation. On the other hand, many estates could 

 be mentioned which apply the best principles in soil conservation 

 and fertilization, and which not only act as experimental centres 

 where new ideas can be put to the test, but serve also as examples 

 to native cultivators in the surrounding country. 



Apart from research on crops, which has been considered above, 

 the problem of cultivation on European-owned estates is mainly 

 that of maintaining fertility in spite of continual or frequent crop- 

 ping. The solution seems to depend on two lines of activity — con- 

 serving the soil and using fertilizers. The first of these has been 

 considered in some detail in discussing native cultivation, and 

 many of the methods mentioned, such as terracing and contour 

 ridging, establishing suitable plants on ridges along contours to 

 hold back soil-wash, and maintaining a vegetal cover on the soil 

 during periods of rain, can be applied even more easily on Euro- 

 pean estates than on native small holdings. 



The use of fertilizers, however, is more important in connection 

 with European estates where it is recognized to be essential. The 

 major problem is to find a fertilizer which the cost of freight 

 from Europe will not make prohibitive. This is essentially an 

 economic rather than a scientific question, but the following notes 

 may indicate the bare outlines of the problem. 



At present the local fertilizer supplies are almost negligible: 

 animal manure is insufficient except in a very small area, and 

 mineral phosphatic deposits are lacking except in South Africa. 

 There is a movement to manufacture bone-meal manure and fish 

 manure as by-products of meat factories and fishing industries, 

 and if the government meat factories are inaugurated as part 

 of the campaign against the overgrazing trouble, there should be 

 no difficulty in disposing of any quantity of fertilizers, if they can 

 be produced cheaply. Another way of obtaining bone is the wide- 

 scale collection of wild and domestic animal remains. In India 

 the organized collection of bones has given rise to a considerable 

 export trade. In Africa where many of the heavily stocked game 

 and cattle areas are littered with skeletons, bone-meal factories 



