THE USE OF FERTILIZERS 95 



Nitrogen is in many ways one of the simplest of 

 plant foods to handle; that is, it is very easy to 

 know when the trees need an additional supply of 

 nitrogen. This may be told both from the growth 

 of stems and the color of the foliage. Whenever 

 a tree is not making reasonably good growth, and 

 when the foliage is sparse and yellow, the need of 

 nitrogen is indicated. Of course, nitrogen may be 

 present in the soil, but unavailable because the roots 

 of the tree stand in water, or for some other reason. 

 Lack of drainage will always interfere with the 

 availability of nitrogen. On the other hand, when 

 a tree is growing vigorously and when the foliage 

 is a thick, heavy, dark green, it is practically sure 

 evidence that no additional supply of nitrogen is 

 necessary In this way the fruit grower is enabled 

 to keep close track of his nitrogen and to add more 

 whenever it is needed. 



Phosphoric acid is especially required in building 

 up the fruit and should be given in relatively liberal 

 quantities when trees have fruit ready for matur- 

 ing. Potash is valuable for the assistance it gives 

 in the physiological processes of growth, enabling 

 the leaves to take up the carbon in the atmosphere. 

 There is also a general theory that potash is very 

 much needed in the formation of seeds and that it 

 should be used liberally, therefore, upon a peach 

 orchard when a crop is maturing. It is thought also 

 to help in giving color. In fact, the general preju- 

 dice is strongly in favor of the use of a liberal 

 amount of potash in fertilizers for peaches. 



FORMS OF FERTILIZERS 



These various chemical elements are available to 

 the farmer in various forms. Nitrogen, for instance, 



