STATE POMOLOGICAL SOCIETY. 



117 



yields also, have been much steadier than those of the other 

 treatments, as shown in the following table, which gives the 

 annual yields from 1907 to 1912, in bushels per plat of about 

 an acre. 



TABLE XII.— INFLUENCE OF CULTURAL METHODS, WITH AND WITHOUT 



FERTILIZATION, ON STEADINESS OF YIELD. 



(Yields in bushels per acre annually, in Experiment 221.) 



In the presence of fertilization in this orchard the differences 

 in steadiness of yield between the mulched and tilled trees are 

 very striking. The tilled trees on the one hand are showing a 

 regular and distinct off year, while those receiving the mulch 

 have shown steady increases in yield up to about 600 bushels 

 per acre, which is followed by a decrease of only about 200 

 bushels. The off year, therefore, has not yet been eliminated 

 entirely, but its influence has been greatly reduced. At the 

 present time, the average deficit on the tilled and fertilized 

 trees in this experiment is practically represented by the losses 

 in their off years. 



The fundamental cause of this difference is very important. 

 Practically it appears that the chief difference in treatment lies 

 in the fact that the tree roots are materially disturbed in one 

 case and not in the other. Strange to say, this disturbance does 

 not seem to have injured the growth, but it, or some other influ- 

 ence not yet recognized, has evidently reduced the yields very 

 materially. The harmful effect on yield that regularly accom- 

 panies too much pruning of the tops of apple trees is now 

 widely recognized. There is therefore reason to believe that 

 similarly harmful effects may be associated with any regular 

 and material pruning of the roots. 



