FACTORS AFFECTING NUTRIENT CONTENT OF APPLE FOLIAGE 



William J. Lord 

 Department of Plant and Soil Sciences 



Crop size can have a considerable effect on the quantity of 

 several elements in apple foliage. Leaves from a tree with a large 

 crop will contain more nitrogen (N) and less potassium (K) than 

 leaves from a tree with a light crop. Leaves from a light-crop 

 tree may contain 0,2 to 0,3% less N than when the same tree has a 

 full crop. Leaves may decline as much as 0.41 K in a heavy-crop 

 year. Calcium (Ca) follows the same trend as N and exhibits about 

 the same difference as N in leaf content between the light- and 

 heavy-crop years. Leaf magnesium (Mg) is slightly higher in a 

 heavy-crop than in a light-crop year. Crop size has little, if 

 any, effect on leaf phosphorus (P) . 



The amount of one element may affect the amounts of other 

 elements in the leaf. For example, leaves which are relatively 

 high in N tend to have lower levels of K and P and higher levels 

 of Mg and Ca than leaves from trees which have a low to medium 

 level of N. High levels of K may depress leaf Mg and Ca, particu- 

 larly if the soil supply of Mg and Ca are low. However, moderate 

 levels of K do not seriously depress Mg as long as there is an 

 adequate level of Mg . 



Another factor which may influence the leaf content of some 

 elements is soil moisture or rainfall. Leaf K is generally lower 

 in dry growing seasons than in years with adequate soil moisture. 

 Mg is generally lower in years which have above normal rainfall 

 during the early part of the growing season. The magnitude of the 

 change in leaf content caused by seasonal rainfall will depend 

 upon the relative wetness or dryness of the season and the supply 

 of nutrients in the soil. If the soil is so wet or so dry that 

 development of new roots is prevented, the leaf content of essen- 

 tial elements could be reduced. 



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POMOLOGICAL PARAGRAPH 



Use of ethephon to promote color and ripening of apples in Massa- 

 chusett~s^ Our suggestions for use of ethephon for promoting uni- 

 form ripening and red color of apples have not changed from last 

 year. These suggestions were published in Fruit Notes 40 (No. 4): 

 July/August, 1975. Those who do not keep back issues of Fruit 

 Notes can obtain a copy of the suggestions on ethephon usage from 

 your Regional Fruit Specialist. 



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