-18- 



Table 1. The effects of cropping on growth, and leaf and fruit 

 nutrition of apple trees. 



Measure 



Heavy cropping trees in comparison to 

 non-bearing or light - cropping trees 

 will have: 



Vegetative growth 

 Nutrient uptake 



Leaf N 

 Fruit N 



Leaf K 

 Fruit K 



Leaf Ca 

 Fruit Ca 

 Leaf Mg 

 Fruit Mg 

 Leaf P 

 Fruit P 



Less shoot and root growth . 



Less uptake of elements because of 

 restriction oi' root growth. 



Higher leaf N 



No effect but if fruit N too high 

 quality will be reduced. 



Lower leaf K 



Lower fruit K because of large demand 

 of fruits for this element 



High leaf Ca 



Higher fruit Ca 



Slightly higher leaf Mg 



Little, if any, effect 



Little, if any, effect 



Little, if any, effect 



Leaves from a large crop tree may contain 0.2 to 0.3-0 more N 

 than when the same tree has a light crop. K in leaves may decline 

 as much as 0.4% in a heavy crop year. Leaf 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 Mg is slightly 

 higher in a heavy crop than in a light crop year. Crop size has 

 little, if any, effect on leaf P. 



Total K absorbed and the total dry matter produced is similar 

 for fruiting and non-fruiting trees but in heavy-cropping trees 

 is translocated into the fruits. Thus, the demand of a large crop 

 for K is great and both the tree and fruit may be deficient in 

 this element. Leaf injury because of K deficiency can cause pre- 

 harvest drop and reduce fruit size. In contrast, light cropping 

 trees are probably much higher in K than is needed because of 

 "luxury" uptake. 



