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 production. 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 $160 per acre annually. 

 The accompanying increases in growth and general vigor ot 

 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 re- 

 sponses can be secured in any particular orchard. 



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

 ductions 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 oe 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 

 m.uch misconception and misinformation. It is not uncommon 

 to hear that apples consist almost entirely of water, one 



