316 SOILS 



The chief disadvantages of a too rigid adherence 

 to single-crop farming are the unequal distribution 

 through the year of labour and of returns, and the 

 certain exhaustion of the soil sooner or later, by 

 almost continuous cropping with one plant or close- 

 ly related plants. Single-crop farming, if persisted 

 in, means ruin. Diversified farming is one of the 

 strongest props of soil fertility. Undoubtedly the 

 farming in some sections of the country, especially 

 the far West, must be single-crop, or practically so, 

 in order to be profitable, for the farmer must grow 

 what he can sell at a profit. But other crops 

 should be introduced wnenever possible. It is 

 very hard to persuade the farmer who has been 

 growing corn, or wheat, or cotton, and little else, that 

 it will be for his interest to diversify his farming. 

 These have been his money-making crops. Yet 

 the time always comes when he is forced, by the 

 lessening fertility of his soil, to introduce "green 

 crops," to feed more stock, and to rest his over- 

 worked land. 



KEEPING LIVE-STOCK TO MAINTAIN FERTILITY 



Theoretically, the most economical way of 

 maintaining tne fertility of the soil is by growing 

 crops to feed live-stock and returning their excre- 

 tions to the soil; practically, this is the most en- 

 during method. If all the conditions for caring 

 for and applying manures were perfect, from 70 to 

 90 per cent, of the plant food in what the animals 

 eat would be returned to the soil in the manure and 

 urine. Practically a much smaller per cent, than 

 this is recovered, for there is always loss in storing 

 and handling manure. But even granting that the 

 percentage of plant food that can be recovered in 



