Boron deficiency is an uncommon disorder affecting plants growing in deficient soils and is often associated with areas of high rainfall and leached soils. Boron may be present but locked up in soils with a high pH, and the deficiency may be worse in wet seasons.
Symptoms include dying growing tips and bushy stunted growth, extreme cases may prevent fruit set. Crop-specific symptoms include:
Rough, cankered patches on roots, internal brown rot.
Distorted leaves, hollow areas in stems
Poor development of curds, and brown patches. Stems, leafstalks and midribs roughened.
Leaf stalks develop cracks on the upper surface, inner tissue is reddish brown. Stem crack develops along vascular tissue.
Leaf stalks develop cracks on the upper surface, inner tissue is reddish brown.
Brown or grey concentric rings develop inside the roots.
Boric acid (16.5%boron), borax (11.3% boron) or SoluBor (20.5% boron) can be applied to soils to correct boron deficiency. Typical applications are about 1.1 kg/hectare or 1.0 lb/acre of actual boron. Borax, boric acid or Solubor can be dissolved in water and sprayed or applied to soil as a dust. Excess boron is toxic to plants so care must be taken to ensure correct application rate and even coverage. Leaves of many plants are damaged by boron; therefore, when in doubt, only apply to soil.
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