No. 6. DEPARTMENT OF AGRICULTURE. 383 



as appear in the solid-colored variants from the Gravenstein and 

 20-Ounce. These points also are discussed iu our Annual Keport 

 for 1910-11, but space is too limited for further consideration here. 



RELATION OF FERTILIZER TO SIZE 



Again referring to Tables \' and Vi, we see that nitrates have 

 apparently reduced the average size of the fiult. Phosphates have 

 given only a slight benefit, if an}-; while potash and manure have 

 given quite important increases. This apparent benefit from potash 

 is interesting, and it may indicate an actual fact, since size depends 

 so much upon moisture and potash has been credited physiologically 

 with the ability of increasing the osmotic power of plant cells. 



All these apparent inlluences on fruit-size, lioweve^', must be 

 considered in their lelation to the size of the crop on the trees. A 

 year ago, we plotted a number of curves from data given in connec- 

 tion with a fertilizer experiment at the New Jersey Station, in 

 order to determine definitely, if possible, whether any relation exist- 

 ed bet^^'een these two factors — fruit-size and size of the crop on the 

 tiee. We found that no correlation exists below what we may call a 

 certain critical point, and that, under the New Jersey conditions, the 

 number of fruits on even moderate-sized trees had to exceed about 

 1,400 per tree before any perceptible correlation appeared. Above 

 this critical j^oint, however, it is probable that ci op-size is the dor- 

 mant influence on the si:::e of the fruit, though the exact position of 

 the critical point may doubtless be raised or lowered somewhat by 

 local conditions of moisture, plant food, etc. 



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 be- 

 fore 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 re- 

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

 reduction in total weight of apples at least for that year. Excep- 

 tions to this may appear in varieties of extra large sizes, or in sea- 

 sons 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 influence. It is 

 here that such factors as fertilizers, culttiral methods, moisture-st<p- 

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

 such a way as to materialh' 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 influence on fruit-size. We also may mention here the factors 

 of pollination and number of seeds per fruit, Avhich have been found 

 to affect fruit-sized by Frost and Muller-Thurgau in Germany. 



A SUGGESTION FERTILIZER FORMULA, WITH CONDITIONS AND TIME 



FOR APPLICATION 



Having thus seen something of the possibilities of fertilizeis in 

 orchards, it remains to point out some of the practical applications, 

 in general, we maj' say that where there is probability that jjlant 



