Fertilizing the Commercial Apple Orchard 191 



fruit is secured. It is found by reducing tillage, pruning 

 and other stimulating operations, that one automatically 

 reduces the relative proportion of raw sap and nitrogen 

 and allows the increased leaf areas to manufacture more 

 concentrated food, such as sugars and starches. As a 

 result, such trees begin to form buds, produce fruit and 

 thereby pass into the second class. 



In the third group or class of trees, the nitrates have 

 become much reduced in proportion to the carbohydrates. 

 As a result, the leaves become yellow and thin, the spurs 

 begin to die and the set of fruit is poor. The trees are 

 starving for nitrates amid plenty of sugars and starches. 

 This explains how a relatively small amount of nitrate 

 added in the spring often produces such remarkable results. 

 It once more restores the balance between the carbohydrates 

 and the nitrates. When a proper balance is seemingly 

 reached between these two, the proper vegetative growth 

 and fruitfulness is secured. Such trees then would be 

 classed in Group 2 and, therefore, approach the ideal con- 

 dition for fruitfulness. Every effort should be made to 

 maintain them in this condition. Good cultivation, the 

 growth of legumes or moderate applications of nitrate of 

 soda will usually serve to maintain the proper balance 

 between the nitrates and carbohydrates. Acid phosphates 

 may also be necessary. 



Experiments in Pennsylvania. 



In a series of experiments carried out under the direc- 

 tion of J. P. Stewart in Pennsylvania, the following con- 

 clusions seemed to be more or less definitely established: 



1. It was found that nitrogen, of all food elements, was 



