ANIMAL INDUSTRIES IN AGRICULTURE 143 



North America, have so far lost their original rich stores of fertility 

 that the best means, in the absence of cheap fertilisers, of aiding 

 in the work of restoration is to introduce live-stock farming in 

 combination with cropping. 1 Thus, through the impetus given 

 by diminishing fertility under a prevailing one-crop system, the 

 advance of population and settlement leads to a sub-division of 

 very large farms and a general transition to a more mixed type of 

 farming with stock-rearing and dairying as prominent features. 

 Some distinction needs to be drawn between horses kept for work, 

 and food-producing animals. The former utilise a considerable 

 part of the food they consume in the production of working energy, 

 which, though it benefits the land by cultivation, disappears as a 

 tangible product with the performance of the work. Horses are, 

 of course, fairly numerous on pure crop farms, but they add little 

 to soil fertility and the grain they consume must be regarded as 

 a necessary deduction from the gross production. Meat and milk- 

 producing animals, on the other hand, expend a small part of the 

 total nourishment consumed in physical energy and a considerable 

 amount in the production of proteids and fats. Indeed the aim of 

 the science of breeding tho various classes of these animals, whether 

 cattle, sheep, or pigs, is to develop the capacity for converting 

 feedstuff s into milk and meat at the expense of that expended as 

 mere maintenance rations or in useless physical energy. 



Not only cereal crops, but also cotton and linseed or flax, as now 

 grown in various temperate and warm temperate regions, are apt 

 to lead to soil exhaustion. Large quantities of cotton-seed and 

 linseed, in addition to the fibres, are exported. In the majority 

 of cotton and flax growing regions fertilisers are but little used, 

 nor are domestic animals kept to any extent. Some of these 

 regions, though originally rich, have become partially exhausted, 

 and require treatment similar to that found necessary in the over- 

 cropped cereal regions. It is significant that the United States 

 Department of Agriculture is recommending farmers in the cotton 

 belt to take up stock-farming for beef production and dairying 

 purposes. 



It is impossible to disregard the question of the supplies of 

 fertilisers as affecting the production of human food, whether of 

 animal or of vegetable origin. The maintenance of a high standard 

 of production per unit of area must depend upon returning to the 

 soil in some direct or indirect form an equivalent of the plant -lood 

 elements taken from it by crops or in other ways. 



Viewed as a whole, agricultural lands throughout the world 

 suffer loss of fertility in the following special ways : first, by the 

 washing of soluble fertilising elements from the soil by drainage 



1 Experiments conducted at Rothamsted point to the conclusion that when 

 land is continuously cropped in successive years without the addition of 

 fertilisers, the yield falls rapidly in the first few years, but afterwards remains 

 fairly constant at a low level. 



This rate of yield would probably be unprofitable under ordinary practical 

 farming conditions. 



