188 POMOLOGY 



trogen in a soluble form when an orchard is low in vitality. 

 Such a treatment is of much more importance to an or- 

 chard which is not tilled since it has been shown that the soil 

 nitrates are likely to be greatly reduced under those cir- 

 cmnstances. This, of course, will depend on the conditions 

 of the soil and perhaps on the climate, for some notable cases 

 are on record in which an application of nitrogen to a culti- 

 vated orchard gave immediate and striking results. If an 

 orchard experiment is continued for a very long period, the 

 time is likely to come when nitrogen may be applied with 

 profit whatever the cultural system followed. 



In point of efficiency in maintaining the growth and yield 

 of the trees, nitrogen stands alone among the artificial fer- 

 tilizers. 



159. Nitrate of soda. — This carrier of nitrogen is more 

 commonly used than any other because of its solubility. 

 The results are usually prompt and marked. When this 

 fertilizer is used alone, it often gives as good results for the 

 first few years as when in combination with carriers of phos- 

 phoric acid and potash. However, over a series of years, 

 a complete fertihzer is considered best. The amount nec- 

 essary varies with the age of the trees, their condition, and 

 the type of soil involved. Nitrate of soda is also used as a 

 special "stimulant" for trees that are sub-normal as a result 

 of injury, having been employed with success on winter- 

 injured trees, those hurt by fire or other agencies. 



For mature apple trees, the usual application is from 4 

 to 6 pounds to a tree or approximately 150 to 200 pounds 

 to an acre. Smaller trees receive proportionately less unless 

 the application is made over the entire orchard surface. 

 For the peach, an application of 2}^ to ^Yz pounds to a 

 tree is usually sufficient. 



160. Sulfate of ammonia is also a readily available form 

 of nitrogen and from a knowledge of its effects on other 



