Manganese (Mn)

Another frequently overlooked mineral is manganese. It is an essential nutrient with multiple nutritional roles, but is susceptible to being rendered unavailable to growing plants in calcareous soils. Calcium can be so antagonistic to plant uptake in some cases that manganese seed treatments and/or foliar sprays are the only solution. In turn, excess amounts of manganese can prevent plant uptake of cobalt, leading to an induced Mn deficiency causing Vitamin B12 deficiency in growing livestock.

This is yet another incidence of the dangers of excess tillage in delicately balanced soils. Deep ploughing into underlying limestone or chalk can raise the natural pH from 7.0 to 8.5. The soil reserves of manganese then become permanently locked-up and any organic matter that might have helped the situation is also lost in the process. To illustrate the case, a soil content of 20 parts per million (ppm) is sufficient to provide adequate manganese to a crop in a soil with a pH of 6.0. At a pH of 7.0 the crop needs soil with 70ppm Mn and at pH 8.0 it needs 110ppm. The most susceptible crop is oats and the deficiency symptoms are poor growth, grey leaf spot (Grey Speck) and poor flower and seed set.

If there is enough manganese in a soil to grow good grass and crops, there will be more than enough for livestock. This means that manganese deficiency in livestock is a fairly rare occurrence in the UK. However, it is worth noting that excess amounts of calcium and phosphorus in cattle feed can induce a deficiency.

Manganese Deficiency in Plants

Chlorosis in leaves of wheat and barley amongst others
Grey Speck, poor flower and seed set in oats
Yellowing of particularly young leaves in sugar beet (difficult to spray but element soil dressings ideal)
Black marking on underside of potato leaves
Marsh spot in peas

Manganese Deficiency in Livestock

Poor bone development in young stock
Possible skeletal defects
Some weight loss
Poor co-ordination in new-born stock (ataxia)