CHAPTER VI. 



THE SILAGE SYSTEM HELPS MAINTAIN SQIL 

 FERTILITY. 



When the cattle feeders of this country once thoroughly realize 

 that they can profitably feed or raise stock by means of the silage 

 system, the great problem of maintaining and increasing soil fer- 

 tility will be largely simplified for the humus in manure will open 

 up close soils, ventilate all soils, set up bacterial activity to unlock 

 stored up plant food, help warm the soils, retain moisture, mellow 

 up fields and furnish plant food for growing crops which properly 

 balanced and supplemented will maintain the soil for maximum 

 crop production. 



This statement is based on certain fundamental facts, which 

 Farmer's Bulletin No. 180 covers briefly as follows: 



"WTien subjected to proper chemical tests or processes every 

 substance found on our globe no matter whether it belongs to the 

 mineral, vegetable or animal kingdom may be reduced to single 

 elements, of which we now know over seventy. Many of these 

 elements occur but rarely, and others are present everywhere in 

 abundance. United mostly in comparatively simple combinations 

 of less than half a dozen each, these elements make up rocks, 

 soils, crops, animals, the atmosphere, water, etc. The crops in 

 their growth take some of the elements from the soil in which 

 they grow\ and others from the air. Many elements are of no 

 value to crops; a few, viz., 13 or 14, are, on the other hand, abso- 

 lutely necessary to the growth of plants; if one or more of these 

 essential elements are lacking or present in insufficient quantities 

 in the soil, the plant cannot make a normal growth, no matter in 

 what quantities the others may occur, and the yields obtained 

 will be decreased as a result." 



The problem of the conservation of soil fertility is therefore 

 largely one of maintaining a readily available supply of the essen- 

 tial plant elements in the soil. Most of these elements occur in 

 abundance in all soils, and there are reajly only about three of 

 them that the farmer need seriously consider — nitrogen, phos- 

 phoric acid and potash. Of these, the latter two are mineral com- 

 pounds which are very often lacking in the soil in sufficient 

 quantity to give profitable crops and they must therefore be sup- 

 plied in the form of manures or fertilizers. The nitrogen is partly 

 obtained from the air by leguminous crops, but the supply from 

 this source is limited and the proper enrichment of the soil often 

 demands the addition of this compound. 



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