-25- 



sprayed with these materials may contain high levels 

 of Mn, but much o£ this represents inactive contamin- 

 ation. 



9. Cu_. Optimum levels o£ Cu are in the range of 7.5 to 12 

 ppm. Leaf concentrations below approximately 3.5 ppm 

 are deficient. High soil pH and/or high P levels may 

 aggravate Cu deficiency. Cu can be added to the fertilizer 

 but this is usually less effective and more expensive 

 than a spray of a fixed-copper fungicide applied between 

 green-tip and 1/4-inch green. Delaying this spray to 

 1/2-inch green may result in fruit russeting. 



10. IrGn(Fe).F e is not usually a problem and leaf concentrations 

 vary considerably depending on several factors. Levels 



of 50 ppm appear to be adequate under most circumstances. 

 High levels of Fe in relation to Mn may be used as an 

 indicator of Mn deficiency, i.e. if Fe/Mn ratios approach 

 or exceed 2.0. 



11. Sulfur is not included in most leaf analyses but require- 

 ments are believed to fall in a range between those for 



P and those for Mg , i.e. approximately 0.2-0 + leaf con- 

 tent. Responses obtained from soil applications of gypsum, 

 or sulfate of potash magnesia, or foliar sprays of Epsom 

 salts suggest that at least a part of the response to such 

 treatm.ents may be related to sulfur. Until more definite 

 information, pro or con, about sulfur requirements is 

 developed, it would appear appropriate to rely on sulfate 

 forms of other nutrients to supply this element. 



Combinations of Deficiencies 



It is common to find two or more elements involved in a parti- 

 cular orchard nutrition problem. These combination problems may 

 involve low K plus low Mg , low B plus low Zn ; low Mg plus low Zn; 

 high P p lus low Zn qr_ low Cu among others. In a few such cases, 

 the cause of the problem may be a matter of imbalance, but in most 

 instances the amounts of each of the elements available to the 

 trees can be considered independently. 



For example, if both K and Mg are in short supply, application 

 of both will be required. The apparent aggravation of a Mg short- 

 age by increased application of K indicates a need for increasing 

 the supply of Mg rather than limiting the supply of K. 



Another common problem involves B and/or Zn shortages. Young 

 trees that are flowering heavily for the first time or that bore 

 their frst heavy crop during the previous season may show varying 

 degrees of shoot dieback resembling winter injury. Examination of 

 these trees usually shows that the cambium has not been damaged 

 by cold. 



