Damon Boynton 293 



Since nitrogen responses may be modified by so many things other 

 than the nitrogen supply, critical systematic evaluation of the most 

 likely of the modifying influences is frequently essential to a complete 

 understanding of the nitrogen response of a Mcintosh apple tree in a 

 particular year. This is especially important when it is necessary to 

 unravel the complex of possible reasons for failure of the tree to respond 

 to nitrogen in the way that somebody thinks it should. Why did it 

 grow more or less than expected? Why did it bloom in this year and 

 not that? Why was the fruit large or small in spite of this or that? Why 

 was the fruit quality better or worse than anticipated ? These questions 

 often cannot be answered without specific knowledge, not only of the 

 temperature, light, and moisture conditions of the previous two grow- 

 ing seasons, but also of the internal drainage and moisture reserve of 

 the soil, the insect, disease, and spray injuries to which the foliage ot 

 the tree was subjected, and the status of the tree with respect to nu- 

 trients other than nitrogen. The more exact this knowledge is, the more 

 easily special limiting conditions can be sorted out of this group of 

 possible ones. While there is still much to be done, steady progress has 

 been made in the understanding of these complicating factors and in 

 the recognition of diagnostic criteria for them. 



Thus, the success with which a New York Mcintosh apple grower 

 copes with the problem of controlling the nitrogen effects on his trees 

 will vary from year to year depending on weather, and other condi- 

 tions beyond his control; but, on the average, accuracy in diagnosis and 

 skill in manipulating the cultural conditions in the orchard will point 

 him toward maximum yields of the highest quality fruit. It is the 

 business of the pomologist to help him with such practical problems 

 in plant nutrition, and I have tried in this paper to outline briefly the 

 general approaches that we are using in New York. 



