For example, a soil may be rich in organic ammonia 

 from vegetable matter turned under as green manure, 

 and through a late wet spring fail to supply the avail- 31 

 able Nitrate in time to get the crop well started before 

 the hot, dry, summer season sets in. In this case the 

 use of Nitrate of Soda alone will force growth to the 

 extent of fully establishing the crop against heat and 

 moderate drouth. This method of manuring is simply 

 Top-Dressing, familiar to us all. 



Nitrate as plant food seems to in- 

 fluence more especially the develop- Special Influ- 

 ment of stems, leaves, and roots, which on^EcTble Value 

 are the framework of the plant, while O f piant. 

 the formation of fruit buds is held in 

 reserve. This action is, of course, a necessary pre- 

 liminary to the maturity of the plant, and the broader 

 the framework, the greater the yield at maturity. The 

 color of the foliage is deepened, indicating health and 

 activity in the forces at work on the structure of the 

 plant. Nitrates also show markedly in the economic 

 value of the crop; the more freely Nitrates are given 

 to plants the greater the relative proportion in the 

 composition of the plant itself, and the most valuable 

 part of all vegetable substances, for food purposes, is 

 that produced by Nitrate of Soda. Nitrate is seldom 

 used in sufficient quantities in the manufacture of 

 "complete fertilizers." Hence the general dissatisfac- 

 tion with their use. 



Potash as plant food seems to influence more par- 

 ticularly the development of the woody parts of stems 

 and the pulp of fruits. The flavor and color of fruits 

 is also credited to potash. In fact, this element of 

 plant food seems to supplement the action of Nitrate 

 by filling out the framework established by the latter. 



Phosphoric Acid as a plant food seems to influence 

 more particularly the maturity of plants and the pro- 

 duction of seed or grain. Its special use in practical 

 agriculture is to help hasten the maturity of crops likely 

 to be caught by an early fall, and to supplement green 

 manuring where grain is to be grown. It is frequently 

 used in unnecessary excess in "complete" fertilizers. 



The natural plant food of the soil comes from many 



