soil, SESSION. 99 



tion. This application has increased the i2-year average yield, over that 

 of unfertilized land alongside, by 4.33 bushels each of corn and oats, 1.89 

 bushels of wheat and 646 pounds of hay. 



On another plot the cereal crops have received for each rotation 

 320 pounds of acid phosphate and 260 pounds of muriate of potash, with 

 the result that the yield of corn has been increased by 12.22 bushels, 

 that of oats by 11.43 bushels, that of wheat by 8.68 bushels and that of 

 hay by 997 pounds. In other words, the average increase from the 

 mineral fertilizers has been about three times as great as that from 

 the fertilizer carrying nitrogen only. 



On a third plot the same quantities of nitrate of soda, acid phosphate 

 and muriate of potash have been combined, with the result that the 

 yield of corn has been increased by an average of 16.18 bushels, that of 

 oats by 18.72 bushels, and that of wheat by 15.50 bushels. This increased 

 yield of corn is practically equal to the sum of the increases from the 

 separate applications of the nitrogenous and mineral fertilizers, but those 

 of the other crops are very much greater than this sum. 



If we estimate the value of corn at 50 cents a bushel for the grain 

 and $3.00 per ton for the stover ; that of oats at 30 cents a bushel and 

 $2.00 per ton for the straw; that of wheat at 80 cents a bushel and 

 $2.00 per ton, and that of hay at $8.00 per ton, the combined increase 

 from the diflferent crops of the rotation would have a total value of $7.80 

 for the nitrogen alone, $21.23 ^o'* ^^^ phosphorus and potassium, and 

 $35.88 for the complete fertilizers, thus bringing out very forcibly the 

 need of phosphorus and potassium, as well as of nitrogen, to restore the 

 fertility of this exhausted soil. 



The humus of the soil is, therefore, the great storage battery of 

 its elements of fertility, mineral as well as nitrogenous. It is in this 

 store, chiefly or altogether, that our crops find their sustenance. When 

 this store is exhausted they starve, and in proportion as it is reduced do 

 they suffer from hunger. This humus is the result largely, if not chiefly, 

 of the growth of miscroscopic organisms, working through eons of time. 

 Under natural conditions it slowly accumulates, but when these condi- 

 tions are disturbed it may be wasted so rapidly that a few years may suf- 

 fice to exhaust stores of fertility that have been ages upon ages accumu- 

 lating. 



This does not mean that the character of the original rocks, from 

 which a soil's mineral constituents have been derived, is a matter of no 

 consequence. The superiority of soils to whose formation limestones 

 have contributed is a matter of universal experience, and if these lime- 

 stones have contained phosphatic deposits, as in the case of the famous 



