132 SILAGE SYSTEM MAINTAINS FERTILITY. 



Every time that a crop is grown it robs the soil of a valuable 

 portion of these fertilizing elements. A ton of clover hay, for in- 

 stance, contains 41.4 pounds of nitrogen, 7.6 pounds of phosphorus 

 and 44 pounds of potasl;i. These elements form the basis of the 

 market value of commercial fertilizers and because of the enoi'- 

 ■"mous quality of fertilizer now used they each ha-ve a definite and 

 fairly stable market value. For our purposes in this discussion 

 we place these, values as follows : 18 cents a pound for nitrogen, 

 5 cents a pound for phosphoric acid and 5 cents a pound for 

 potash. It should be remembered that these values are likely to 

 differ to some extent in various localities according as they are 

 affected by the item of transportation. At the present time, be- 

 cause of the Eurojpean War, it is hard to estimate the value that 

 should be placed on these elements, as the sources of most of our 

 nitrogen and potash are very largely controlled by the warring 

 nations, and for this reason our values will be found very con- 

 servative and even very low. But taking one year with another 

 and reaching over a period of years it is fair to assume that the 

 prices of 18, 5 and 5 cents a, pound respectively will be found ap- 

 proximately correct. Now, figured on this basis, it will be found 

 that each ton of clover hay takes from the soil $10.23 worth of 

 fertility. A 100-bushel com crop contains 148 pounds of nitrogeii, 

 23 pounds of phosphoric acid and 71 pounds of potash valued at 

 $31.34. In other words, that much fertility is removed from the 

 soil with every 100-bushel corn crop. In the same manner, the 

 fertility in a ton of wheat has a value of $9.79; a, ton of wheat 

 bran, $14.06; a ton of alfalfa hay, $10.07; a ton of timothy $5.97 

 and a ton of oats, $8.85. Other crops vary In proportion. 



The above figures may be startling to some who have been 

 growing and selling these crops. The question may come up, do 

 these figures actually mean that we can get returns of $14.06 by 

 the application of one ton of wheat bran to our land as a fertilizer? 

 Such is not their meaning, however. They do not mean that if a 

 farmer seeks to restore to the soil the same amount of fertility 

 as was extracted by his 100-bushel corn crop, such fertilizer 

 would cost him on the market not less than the amount stated 

 above, viz.: $31.34. The , same relative values obtain with the 

 other crops mentioned. 



It Is clear, therefore, that unless these elements are put back 

 into the soil in some way, it will produce steadily declining crops 



