152 Principles of Plant Culture. 



out working harm. Nitrogen, however, which aside 

 from water is the most potent food constituent, must 

 be used with some discretion. 



249. Excessive Nitrogen Stimulates Growth at the 

 expense of flowers, seed and fruit. In crops grown for 

 these parts, therefore, fertilizers rich in nitrogen must 

 be used with caution. Apple, pear and quince orch- 

 ards liberally manured with such fertilizers produce an 

 excessive, over-succulent growth of wood, that is sub- 

 ject to blight and winter injury and forms compara- 

 tively few fruit buds. Grain under similar conditions 

 forms long, weak straw, with poorly-filled heads. 

 Grape vines on over manured ground produce excessive 

 wood with few and late-ripening bunches. 



There is little danger of over-manuring, however, 

 with crops grown for parts other than flowers, fruit or 

 seed, so long as decomposed stable manure is used 

 (251). But the more concentrated animal manures, as 

 those from poultry and the hog, the chemical com- 

 pounds of nitrogen, as nitrate of soda and sulfate of 

 ammonia (261), and the so-called "high-grade" com- 

 mercial fertilizers must be used with caution, as they 

 may destroy the plants if applied in excess. 



B PLANTS AS AFFECTED BY INSUFFICIENT FOOD. 



250. It is difficult to separate the effects of a lack of 

 food from those of a lack of water, since the food is 

 mainly conveyed to the plant in the soil water (62). 

 But even with a proper water supply, if one or more 



