WINTER MEETING. 



195 



The values attached to the three fertilizing ingredients in the table 

 on page 191 are not fictitious, but are prices we have to pay in the 

 market for these materials when purchased in commercial fertilizers. 



It will be observed that a large proportion of the plant food re- 

 turned to the soil, in an available form, consists of nitrogen — costing 

 on the market nearly four limes as much per pound as either potash 

 or phosphoric acid. It is now well established that a large part of 

 this nitrogen is derived by these plants from the air, hence it repre- 

 sents so much clear gain in soil fertility. 



It may be urged that the growing and bearing orchards do not 

 require such large quantities of nitrogen as are furnished by clover and 

 cow-peas, and that by the continued use of these crops for green ma- 

 nures we feed the trees an unbalanced ration, which, in the end, will 

 prove detrimental to their bearing qualities. 



An investigation of this phase of the question will readily discover 

 the unsoundness of these objections. For example: to grow apple 

 trees (without the fruit) 7 pounds of nitrogen are required for every 

 pound of phosphoric acid, and for every three pounds of potash. For 

 peach trees the proportions are 4 pounds of nitrogen, 2 pounds of 

 potash and 1 pound of phosphoric acid. In the clover manures, as 

 will be seen by reference to the tables just quoted, the proportion of 

 these ingredients is: for red clover 2 pounds of nitrogen, 1.75 pounds 

 of potash and 1 pound of phosphoric acid, while for the crimson clover 

 the proportion stands, nitrogen 4 pounds, potash 1 pound and phos- 

 phoric acid 2 pounds. In cow-peas the proportion is : 4 pounds of 

 nitrogen, 3 pounds of potash to 1 pound of phosphoric acid. Instead 

 of an excess of nitrogen, there is an actual detficiency. 



Disregarding the growth of the trees and assuming the average 

 yield reported to us by an extensive fruit-grower in Dauphin county, 

 Pennsylvania, an acre of the staple fruits, remove fertility when com- 

 pared with corn (whole plants) from the soil, as follows : 



♦Reported by S. W. Gilbert, of Thayer, Mo. 

 H — 13 



