CHAPTER XVH 



MANURIAL VALUE OF FEEDING STUFFS 



Unless the plant food removed from the soil in crops is returned in 

 some form, after a period of years reduced yields will tell the story of 

 soil depletion. Already over great areas of our country the soil has 

 been so " mined " of its original fertility that only by the liberal appli- 

 cation of commercial fertilizers are remunerative crops now possible. 

 This is shown by the fact that during 1920 there were sold in the United 

 States about 7,000,000 tons of commercial fertilizers, worth about 

 $250,000,000. In the South Atlantic states alone 3,824,000 tons were used 

 in 1918, including hundreds of thousands of tons of cottonseed meal. 

 Southern planters feed great quantities of cottonseed meal to their crops 

 a rational agriculture would combine mixed cropping and stock grow- 

 ing with cotton raising. The meal from the cotton seed would be fed 

 to farm animals and the resulting manure, still rich in fertility, would 

 pass back to the fields, thereby giving a double return. 



A judicious use of commercial fertilizers is highly commendable, but 

 their place in general agriculture is to supplement deficiencies only 

 after all the fertility in feeding stuffs that have been fed to live stock 

 has been wisely and fully conserved. 



432. Farm manure as a fertilizer. Just as with commercial fertilizers, 

 the value of farm manure is computed on its content of nitrogen, phos- 

 phoric acid, and potash, for of the constituents which plants remove from 

 the soil only these need ordinarily be replaced. Phosphoric acid and 

 potash, when naturally lacking in the soil, or when they have been 

 carried off in crops or animals sold, must be replaced by means of com- 

 mercial fertilizers or the manure of farm animals. The nitrogen needed 

 may be indirectly obtained from the air by raising legumes, but in 

 practice much is purchased along with phosphoric acid and potash. 



Not only do farm manures supply plant food, but the vegetable, or 

 organic, matter they contain is important in increasing the productivity 

 of the soil. As this vegetable matter gradually breaks down in the soil, 

 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, etc. The value of organic matter to the soil is shown by the 

 fact that 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. 



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