CHAPTER XVII 



MANURIAL VALUE OF FEEDING STUFFS 



Unless the plant food removed from the soil by the growth of crops 

 is returned in some form, the land will sooner or later be so reduced 

 in fertility that profitable crops eainiot be grown. Already the soil in 

 many once productive areas of this country has been so "mined" 

 that good crops are possible only when commercial fertilizers are 

 liberally applied. In 1913 over $8,000,000 worth of commercial fer- 

 tilizers were sold in the South Atlantic states alone. While the use of 

 commercial fertilizers is wise in some cases, in general farming they 

 should be used to supplement deficiencies only after all the fertility in 

 the feeding stuffs fed to the live stock has been fully utilized. 



Farm manure as a fertilizer. — Farm manure, like commercial fer- 

 tilizers, is valued on the basis of the amount of nitrogen, phosphoric 

 acid, and potash it contains. This is because these are the only plant 

 food constituents removed from the soil by crops which need ordinarily 

 be replaced. The necessary nitrogen may, as we have seen, be 

 indirectly obtained from the air by growing legumes, but in practice 

 much is purchased along with phosphoric acid and potash. 



Not only does farm manure supply plant food, but the vegetable or 

 organic matter it contains also helps to increase the productivity of 

 the soil. As this vegetable matter gradually breaks down, the acid 

 products formed help dissolve and make available to plants some of 

 the otherwise insoluble plant food in the soil. Furthermore, the humus 

 formed from the organic matter of manure helps retain moisture, 

 improves the soil texture, renders it more resistant to wind action, and 

 favors chemical and bacterial action which make plant food available. 

 On fields lacking in humus such crops as rye are often grown and 

 turned under as green manure, for the sole purpose of increasing the 

 humus content. 



Experiments have shown that the fertilizing constituents in farm 

 manure have as high a value as in such high-grade fertilizers as tank- 

 age, bone meal, and muriate of potash. In computing the fertilizing 

 value of feeding stuffs and farm manure, we will therefore use the 

 average market prices of nitrogen, phosphoric acid, and potash in com- 



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