Correct balanced nutrition of the will reduce the incidence of skin disorders and improve the skin finish. Calcium strengthens tuber skins providing better resistance to many diseases. Boron, magnesium and manganese can reduce levels of common scab. Zinc can minimise powdery scab. Sulphur may reduce both powdery and common scab infection.
Calcium strengthens tuber skins providing better resistance to many diseases including black scurf silver scurf, powdery scab or common scab. These independent trials from the UK show the reduction in skin blemishes caused by a number of conditions following treatment with calcium nitrate.
Sulphur helps to reduce the level of common and powdery scab. This effect may be due to a reduction in the soil pH where elemental sulphur is used. Best effects come from applying sulphur to the soil in a readily available form at planting, however a programme of foliar sulphur, can also reduce infection.
This trial from Scotland shows the reduction in common scab following foliar treatment with sulfur compared to untreated.
Boron helps stabilise calcium in the cell walls and also affects calcium absorption, so supplies are important to ensure a balanced nutrition and to maximizes the benefits of applied calcium. This trial shows how boron influences the calcium content of tubers and so also the incidence a range of skin disorders.
Zinc is commonly used to suppress powdery scab where the innoculum is at low levels. However, only soil applications are likely to provide sufficient zinc to have an effect on powdery scab and zinc should only be used as part of an integrated control strategy supported by other agronomic measures to limit soil infection alongside a choice of more resistant varieties.