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stances it is not possible to control the nitrogen effects. Even when 

 rather low rates of nitrogen application are made, the period of time 

 that soluble nitrogen persists in the soil will vary greatly with weather 

 conditions. Heavy winter rainfall following fall fertilization may in 

 one year cause all applied nitrates to leach beyond the rooting zone, 

 whereas following a winter of low rainfall all the nitiates applied dur- 

 ing fall may be available for absorption. Because of this fact and because 

 occasionally serious winter injury to the trunks of trees occurs follow- 

 ing fall fertilization, it has been customary to apply nitrogen fertilizer 

 in the early spring in New York. Late spring and summer applications 

 are not made because they may inhibit fruit color formation and do 

 not furnish available nitrogen at the time it is used in vegetation, fruit 

 set, and initiation of flowers for a subsequent crop. 



The most common method of ground application has been to broad- 

 cast in a ring under the branches of the trees. This has developed as a 

 result of the fact that there is less use of the fertilizer by grass if it is 

 applied in a concentrated band than if it is broadcast over the entire 

 orchard floor. There has been little critical evaluation of this method of 

 application, however, and it is possible that it is not the best under all 

 circumstances. Certainly, the grass cover over the orchard floor deserves 

 some attention and it may be worth while to fertilize it occasionally if 

 not annually. 



The use of urea sprays has recently attracted attention as a method 

 of fertilizing Mcintosh apple trees. Originally suggested in 1942, it has 

 been employed commercially by apple growers rather widely during 

 the past season. Table IV summarizes the results of some comparisons 

 between ground fertilization and urea sprays made on Mcintosh apple 

 trees in 1948. These and other studies indicate that urea spraying is at 

 least as effective as equivalent rates of ground application, in terms of 

 yield, growth, and fruit color and size. The ultimate value of this 

 method of nitrogen fertilization will probably be determined by the 

 efficiency of direct absorption by apple leaves. Preliminary studies indi- 

 cate that half the urea adhering to the leaf surface may be absorbed by 

 the leaf within a few hours of application. Since as much as half of the 

 spray material applied to the leaf may drop off, it is possible that 

 frequently no more than a quarter of the urea applied to the leaves 



