134 HORTICULTURE FOR SCHOOLS 



available source of nitrogen is the atmosphere, the most effi- 

 cient agent for its fixation in the soil being the bacteria which 

 live on the roots of legumes. (3) Since the object in the use of 

 fertilizers is to secure larger net financial returns, the process 

 should never be carried to a point where increased yield is not 

 sufficient to pay increased costs. (4) The state experiment 

 stations have studied the problem of fertilizers for their own 

 localities at first hand, and their publications will give valu- 

 able assistance to the orchardist. 



222. Pruning methods vary somewhat for different species 

 of trees, and sometimes for varieties within a species. They 

 differ also in separate regions. It is not the purpose of this 

 chapter to treat of all pruning systems, but of the principles 

 which are generally applicable. 1 



223. Pruning young trees. As has been stated, when the 

 young tree is removed from the nursery, a considerable loss 

 of root results. On this account, at transplanting time or 

 shortly thereafter, the top must be reduced to maintain a 

 proper balance of the part above ground with the roots. At 

 this time one must have in mind also the establishing of the 

 permanent form of the tree. It is customary to cut the 

 young tree back to a whip, with the top eighteen to twenty- 

 four inches high (Fig. 88). However, when the young trans- 

 planted tree already has branches properly located on the 

 trunk to form the scaffold branches they may be left and all 

 others cut off. 



In trees pruned to a whip after planting, it is advisable soon 

 after growth starts in the spring or early summer to pinch 

 out the terminal bud of all shoots except the ones desired for 

 scaffold branches. The removing of the terminal buds in the 

 undesirable shoots prevents their growth in length but allows 

 the leaves already produced to remain for shading the trunk. 



1 For more complete information, the student should read such publica- 

 tions on pruning as Kain's Pruning Book, Bailey's Pruning- Manual, and the 

 bulletins on pruning issued by the state experiment stations. 



