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Manganese and Zinc Deficiencies
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Manganese and Zinc Deficiencies
Do you know of an organic way to cure a severe case of manganese and zinc deficiency in citrus trees? I have 10 acres of three year old mandarine trees planted on ex-kiwi fruit ground. Any help would be of great value to me.

Manganese deficiency is most common in peaches and nectarines, while magnesium is most common in citrus. Lack of zinc is mainly a problem in peaches, nectarines, grapes and citrus.

  • Manganese: Soil becomes deficient below a pH of 4.7 and above 7.0. The deficiency shows as yellow leaves, and can be difficult to distinguish from lack of nitrogen or magnesium.
    Treatment: Fungicides containing manganese which may prevent deficiency include Mehram (Polyram) and Mancozeb (Dithane M45), or spray before November with manganese sulphate 6 kg /hydrated lime 8kg /water 100 litres.
  • Magnesium: Soil becomes deficient below pH 6. It shows as chlorosis (yellowing), firstly in older leaves. Necrotic flecking or streaking is also characteristic, along with yellow margins and yellow tips.
    Treatment: Apply magnesium sulphate or use Serpentine superphosphate, 20kg/1000 litres, with 3-4 spray applications at two weekly intervals.
    NB: Magnesium can be supplied via Serpentine Reverted Super Phosphate (the Magnesium is supplied via the Serpentine Rock). This material may not be able to be used for certified organic production (check with the relevant standards). Serpentine rock on its own will be more acceptable. Sourcing the material could pose a problem, it is less commonly produced these days.
  • Zinc: Soil becomes deficient below a ph of 4.7 and above 7.5-8.0. Young leaves are usually bunched like a rosette and may be thin and pale, green or yellow, the symptoms vary between plant species, eg little leaves in stone fruit and mottling in citrus.
    Treatment: Use zinc-containing fungicides like Mancozeb (Dithane M45) or use sprays of zinc chelate 1-2kg/1000 litres of water, soon after leaves emerge.

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