The most common nutrient deficiencies in crucifers are:
Molybdenum – Causes whiptail and blindness (no apical growing point) of broccoli and cauliflower. Leaves are extremely malformed, being narrow with curled, ruffled edges. Curd development is poor.
Boron – Symptoms occur as cabbage and cauliflower approach maturity. The pith becomes cracked and brown. In cauliflower, the curd may become brown. Radish roots become distorted and an internal brown discoloration occurs. Scabby surface cankers may appear on radishes.
Magnesium – Chlorosis occurs on interveinal areas of lower leaves. Necrotic spots may occur in the chlorotic tissue. Growth is reduced.
Conditions for Disease Development
Acid or alkaline soils may lead to nutrient deficiencies due to the immobilization of nutrients. Some soils are naturally low in specific nutrients. The excessive, or unbalanced, use of fertilizer may also cause some nutrients to become unavailable to the plants.
Use a balanced fertilizer program appropriate to the soil and the crop. Alter soil pH or apply foliar fertilizers to help correct some deficiencies.