Boron deficiency

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
Symptoms include dying growing tips and bushy stunted growth, extreme cases may prevent fruit set. Crop-specific symptoms include:

Beetroot
Rough, cankered patches on roots, internal brown rot.

Cabbage
Distorted leaves, hollow areas in stems

Cauliflower
Poor development of curds, and brown patches. Stems, leafstalks and midribs roughened.

Celery
Leaf stalks develop cracks on the upper surface, inner tissue is reddish brown. Stem crack develops along vascular tissue.

Celeriac
Leaf stalks develop cracks on the upper surface, inner tissue is reddish brown.

Swede and Turnip
Brown or grey concentric rings develop inside the roots.

Treatment
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.