60 CHAPTER IV 



Maintaining Fertility. — The most important economic 

 problem of any extensive agricultural country is to maintain 

 the fertility of the soil. In young countries, where land is 

 plentiful and cheap, this is at first not so evident, but the 

 gradual reduction of the productive power of the land, to- 

 gether with increasing population, must in time compel 

 recognition of this truth. The frequent periods of famine in 

 India, China and Kussia, due largely to improvident methods 

 of farming, afford cases in point. 



The ideal of agricultural practice, in the case of highly 

 productive lands, is obviously to maintain crop yields per- 

 manently at this high level, and, in the case of poor lands, to 

 gradually raise the productivity to a higher level, and then 

 maintain it permanently ; due attention being paid to economy 

 in either case. 



Under highly intensive systems of farming this ideal is 

 comparatively easy of achievement, because relatively small 

 areas are cultivated and crop yields are large, and so more 

 efficient methods of management are possible. 



Over the greater part of South Africa, especially in the 

 summer rainfall area, the farming is largely extensive in 

 nature. In many agricultural districts, truly intensive 

 methods are hardly possible, because, apart from the fact that 

 on the whole the soils are not rich in plant food, the rainfall 

 is extremely erratic in regard to both quantity and distribu- 

 tion. The areas under cultivation are freauently far larger 

 than can be efficiently managed, and as a result the average 

 level of production is extremely low. As a fairly general rule, 

 however, it can hardly be doubted that the adoption of some- 

 what more intensive methods would pay. 



While the maintenance of fertility denends primarily on 

 the plant food relations in the soil, the absolute necessity of 

 good tillage must be kept in mind, and the system of farming 

 practised must be such as will not lead to deterioration in 

 mechanical condition, nor affect adversely the activities of 

 useful soil micro-organisms. 



Soil fertility cannot be maintained in field practice by use 

 of commercial fertilisers alone. On the score of economy, 

 firstly, the idea is untenable, because there are cheaper 

 methods of supplying certain of the requirements : notably 

 in regard to nitrogen, which is the most costly of all commer- 

 cial plant foods. In the second place, commercial fertilisers 

 provide little or no humus, and the inevitable depletion of the 

 soil humus leads to bad tilth and decreased availability of other 

 plant foods in the soil. 



