286 



Mineral Nutrition of Plants 

 TABLE IV 



Comparison of the Effects of Sprays and Spring Ground Applications of Urea 



on the Yield, Growth, and Fruit Characteristics of Mcintosh Apples in 1948. 



Average of Three Experimental Plots in Western New York 



lb. 



0.6 

 1.2 



2.4 



1.0 



!-3 



LD*5 per cent 



1.8 



8.5 0.6 



2.6 



2.0 



*Least difference for statistical significance at odds of 19 to 1. 



"("Twenty shoots per tree were measured at random after growth had stopped. 



jThe percentage of bloom and set on at least 200 vigorous spurs on 4 sides of each tree were 



determined. Since practically all spurs bloomed in 1948, the percentages are based on the 



total number of spurs counted. 



enters them, the rest going to the ground where it is ultimately absorbed 

 by roots. There appears to be far less efficiency in absorption by the 

 upper surface of an apple leaf than by its lower surface, and young 

 leaves seem to be more efficient than older ones. So it remains to be 

 seen whether or not this development can be used to improve our con- 

 trol of the nitrogen nutrition of apple trees. 



Ground cover 



The presence of ground cover may be indirectly important in per- 

 mitting control of nitrogen effects on apple trees. Nonleguminous sod 

 uses large quantities of nitrogen in its growth and can be relied on to 



