STATE POMOLOGICAL SOCIETY. 55 



THE FERTILIZATION OF APPLE ORCHARDS. 



By Dr. John P. Stewart, Experimental Pomologist, State 



College, Pa. 



The experiments started in 1907-8, by the Pennsylvania Ex- 

 periment Station, have shown that the available supply of plant- 

 food in an orchard may be the most important check on its pro- 

 duction. By variations in fertilization alone, we have obtained 

 average increases in yield ranging from 50 to 370 bushels per 

 acre annually for the past 5 or 6 years. This means that, with a 

 valuation of only 50 cents per bushel for the extra fruit, proper 

 fertilization has given us average net returns running up to 

 more than Si 60 per acre annually. The accompanying increases 

 in growth and general vigor of the trees have been almost as 

 marked. 



It is our* present purpose to indicate briefly the general con- 

 ditions under which these results were obtained, and to out- 

 line a simple plan for determining whether or not similar 

 responses can be secured in any particular orchard. 



At the outset we may say that our present results and deduc- 

 tions are derived more or less directly from the results of 13 

 experiments involving 10 soil types, 12 different locations, 

 2653 trees (excluding those strictly on cultural methods), and 

 over 42,300 bushels of fruit in the last 6 years. Only six of 

 these experiments, however, are entirely on fertilization and in 

 bearing, and only the more important results from three of 

 them will be considered here, although the results from all 

 six are summarized. These six experiments involve six soil 

 types, 800 trees, and about 15,300 bushels of fruit in the past 6 

 years. 



The Amounts of Plant Food Actually Taken Up By a 



Mature Orchard. 



Before examining the results themselves, however, it will 

 be well to consider briefly the actual fertility requirements of 

 a mature apple orchard. This is a matter upon which there is 

 much misconception and misinformation. It is not uncommon 

 to hear that apples consist almost entirely of water, one writer 



