No. 6. DEPASTMENT OF AGRICULTURE. 445 



In our judgment, this has a bearing upon the fact that nitrogen 

 has apparently failed to increase the size of the fruit in our experi- 

 ments. The crop-size was raised so much that full size of the fruit 

 was not obtainable. 



It also has an important bearing upon thinning. It means, in 

 general, that if one thins an apple tree of even moderate size before 

 the number of fruits has reached a critical point, which may be 1,400 

 or more, he can hardly expect to modify the size of the remaining 

 fruit, and the most effect of the thinning will be an actual reduction 

 in total weight of apples at least for that year. Exceptions to this 

 may appear in varieties of extra large size, or in seasons or locations 

 that are exceptionally dry. 



It also means that, below the critical or the thinning point, there 

 is opportunity for the other factors to exert their iutluence. It is 

 here that such factors as fertilizers, cultural methods, moisture- 

 supply, and heredity show their effects, and they may co-operate in 

 such a way to materially raise the critical point. This assumes that 

 the variety is properly located in respect to temperature and length 

 of growing season, both of which are factors that may have an in- 

 fluence on fruit-size. We also may mention here the factors of pol- 

 lination and number of seeds per fruit, which have been found to 

 affect fA'uit-size by Ewert and Miiller-Thurgau in Germany. 



SUGGESTIONS ON THE USE OF FERTILIZERS IN ORCHARDS 



The foregoing discussion does not mean that all fertilizers or all 

 orchards will give a profitable response to fertilization. There are 

 too many other limiters for that. Some of our experiments and some 

 treatments have given no important results as yet. This may be due 

 to improper moisture supply, relative youth of some of the treas, or 

 to the action of some other one or more of the many possible limiters. 



All the facts, therefore, emphasize the necessity for local or com- 

 munity trials. It is unsafe for the grower to assume either that all 

 orchards need fertilizers or that no ochards need them. Either of 

 these attitudes, if consistently acted upon, is almost sure to prove 

 costly to its possessor. The only safe attitude is the one that views 

 the orchard like other crops, knowing that lack of available food is 

 undoubtedly the limited at times, and using proper fertilization ex- 

 tensively only where and when it is needed. 



As to what constitutes a proper fertilizer, on the basis of present 

 results, we are suggesting a combination that will carry about 30 

 pounds actual nitrogen, 50 pounds of actual phosphoric acid (PoOg) 

 and about 25 pounds of actual potash (KoO) per acre. Where there 

 is evidence that potash is needed, the above amount may be increased 

 to 50 pounds of K^O. The former amounts are carried in 500 pounds 

 of a 6-10-5 fertilizer, and the latter are given by the same weight of a 

 G-10-10 material. We apply the nitrogen by using 100 pounds of 

 nitrate of soda and 150 pounds of dried blood, thus getting quick 

 action and also one that is prolonged well through the season. The 

 phosphates may be carried in 200 pounds of steamed bone meal or 

 raw rock phosphates; or in about 350 pounds of acid phosphate or 

 basic slag. The potash may be carried in 50 or 100 pounds of muriate 



