Tree Fruit Soils and Nutrition











 

 

The 17 essential elements are: 

C H O P K N S Ca Fe Mg B Mn Cu Zn Mo Cl Ni

Zinc (Zn)

Form used by plants:

Zn2+

Important functions:

  • Component or regulator cofactor of enzymes (dehydrogenase, proteinase, and peptidase enzymes)

  • Influences plant hormone proteins, for example  auxin development, especially IAA (i.e., aids in the normal growth and fruiting processes).

  • Promotes starch formation

Ideal foliage range for apple leaves:

15-60 ppm

Ideal fruit concentration:

Ideal soil range: 

0.5-0.75ppm (available Zn not total Zn levels)

Zinc is not very mobile in soils.

Best indicators: 

Mobility in plant:

Not remobilized within plant

Deficiency symptoms: 

 ZnDef.JPG (11033 bytes)  Zn def apple ros.jpg (29117 bytes) Zn def apple.jpg (29868 bytes)  

  • Young leaves are affected first. 

  • Leaves are smaller and narrower than normal ("little leaf").

  • Rosetting of leaves occurs.

  • Blind wood

Increased risk of Zn deficiencies on:

  • Trees on sandy soils containing limited quantities of Zn

  • Soils high in P and Ca

Excess problems/Interactions with other elements:

  • Excess phosphate may encourage Zn deficiency
  • Heavy N fertilization intensifies Zn deficiency. However, application of N fertilizer can stimulate plant growth and increase Zn requirements.  Acid-forming N fertilizers will increase the uptake of both native and supplemental Zn. Neutral to basic products are known to depress Zn uptake.
  • Excess Zn encourages iron deficiency and reduces manganese absorption
  • Other metal cations, including copper(Cu2+), iron(Fe2+), and manganese (Mn2+), inhibit zinc uptake
  • Application of calcium sulfate added to a slightly acid soil can increase the Zn and Fe concentrations in plants.

 

Updated July 13, 2004

 

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