282 



Mineral Nutrition of Plants 



1942 



1943 



194? 



Figure i. Average annual yield per tree in a New York Mcin- 

 tosh apple orchard under three levels of nitrogen fertilization. 

 Annual treatments: H trees, 1.5 lb. N; M trees, 1.0 lb. N; L 

 trees, 0.5 lb. N. 



to the weather conditions in the period of bloom. In the six years, 1944 

 was the only one in which there was a long period of ideal weather for 

 pollination, and no frost. In 1945, crop failure was the result of frost 

 and cool rainy weather during the entire period of bloom. The years of 

 1946 and 1947 were l ess favorable for pollination than 1942 and 1943, 

 although there was some opportunity in all four years. Thus, weather 

 during the bloom was the most significant factor limiting yield in this 

 orchard. In 1943, 1944, and 1946 the total yields of the low nitrogen (L) 

 trees were significantly less than those of the intermediate nitrogen (M) 

 trees. The direct causes of the decreased total yield due to nitrogen de- 



