182 



POMOLOGY 



Table LIV 



relative amounts of plant-food materials removed by apples 

 and wheat 



Van Slyke has summarized his data for the several tree- 

 fruits and observes that the quantity of nitrogen and pot- 

 ash is about the same in any one kind of tree, while the 

 amount of phosphoric acid is only about one-fourth that of 

 the other two materials.^ 



Nitrogen 30 to 75 pounds 



Phosphoric acid 7 " 18 " 



Potash 33 " 72 " 



Calcium oxide (lime) 38 "114 " 



However, the amounts used by different kinds of fruit- 

 trees vary greatly, as is shown by the table on opposite page. 



According to studies by Thompson,^ "fruit-trees demand 

 plant food more nearly in the proportion in which it exists 

 in the soil than does com or almost any other crop." 



^ Fertilizers and Crops. New York. 1912. 



2 Thompson, R. C. Ark. Agr. Exp. Sta. Bull. 123 (Tech.). 1916. 



