Needs of Fruit Trees. 209 



mand for specific kinds and proportions of soil con- 

 stituents; it is really a continuous cropping of the 

 same kind; there is no opportunity, as in the case 

 of ordinary farm crops, to correct the tendency to 

 exhaustion by a frequent change of crops, or the 

 frequent growth of those which require different kinds 

 and amounts of plant -food constituents. 



"In studying methods of manuring orchards, how- 

 ever, it must be admitted that the general princi- 

 ples of manuring which apply to fruits apply quite 

 as well to farm crops; that is, the essential con- 

 stituents of manures must be the same. A fruit tree 

 will not make normal growth in a soil destitute of 

 nitrogen. That nitrogen encourages leaf-growth is a 

 recognized fact, and, since trees grow by means of 

 both leaf and root, its presence is required in the 

 soil in order to promote the growth and extend the 

 life of the tree. It is very evident, too, that pot- 

 ash is an essential constituent in the growth of 

 fruits, not only because it constitutes a large pro- 

 portion of the ash of the wood of the apple, pear, 

 cherry, and plum, and more than 50 per cent of 

 the ash of fruit, but because it forms the base of 

 the well-known fruit acids ; and in order to nourish 

 a tree properly, as well as to insure proper ripen- 

 ing, phosphoric acid is also very essential, though it is 

 apparent from such investigations as have been made 

 that this constituent is relatively of less importance 

 than for the cereals. 



"It is also a matter of common observation that, 

 in the production of stone-fruits particularly, lime 



