THE SOIL. ii 



Use Legumes for Feed and Return the Manure to 

 the Soil. However, legume plants are always richest 

 in protein, the most important food element, so that 

 they should be grown and used for feed on the farm as 

 far as possible. By so doing a large part of the ni- 

 trogen in the seed and hay of this crop is returned to 

 the soil through the manure. 



Phosphorus. Of the other essential elements 

 phosphorus is the chief one to which the farmer must 

 give thought. It always exists in small amounts in 

 the soil, usually from .03 to .2 of a per cent., and since 



AVERAGE PRODUCTION REDUCED BY INFERTILE SPOTS. 



it is required by all crops and goes chiefly to the seed 

 the supply in the soil is very likely to be exhausted. 

 This supply can be maintained only by lessening the 

 sale of seed or crops containing this element or adding 

 the phosphorus directly in the form of fertilizer. 

 In the case of the cotton crop, for instance, if the seed 

 is brought back to the farm, and used as feed for 

 animals kept on the farm there is little loss of phos- 

 phorus. In dairy states where cream or butter is the 

 chief thing sold there is positively little loss of phos- 

 phorus except by leaching. 



Supplying Phosphorus to the Soil. Untreated or 

 raw rock phosphate (native deposits see chapter on 

 fertilizers), becomes available to plants only very 

 slowly, but is of course much cheaper, and has twice 



