The availability of manganese is influenced by pH and deficiencies are most likely to occur in calcareous soils. Mn is most available between pH 5 and 6.5. At very low pH (< 5), Mn toxicity is possible. Mn+2 is readily chelated by organic molecules which is favoured by a high organic matter content and also reduces Mn availability. Other nutrients such as Cu, Fe, Ni and Zn may inhibit Mn uptake.
Soils with a high granite and sandstone content are naturally poorer than volcanic or sedimentary soils. High organic matter content negatively affects the solubility of manganese. Liming has the same effect. Finally, dry weather is not conducive to the presence of absorbable manganese. In damp soils, such as waterlogged soils during winter months, manganese is identified by bluish-grey stains.
Due to the high mobility of Mn in plants the symptoms are first visible in the young leaves and can be recognized by interveinal chlorosis. It can be confused with Mg or Fe deficiency, but Mn deficiency occurs at the older leaves first and Fe deficiency is marked by a sharper contrast between the green veins and areas affected by chlorosis.
Excess manganese in the soil can negatively affect crops growing in damp soils, or under rainy conditions. The same applies under anaerobic conditions.