The main role for manganese in plants is an a constituent and activator of enzymes involved in protein synthesis, lipid metabolism and photosynthesis. Manganese has an important role in regulating photosynthetic enzymes, and so, deficiency leads to a reduction in photosynthetic efficiency which can cause a progressive decline in dry matter productivity and yield. Manganese deficiency is widely acknowledged to be the most widespread micronutrient problem in arable crops in the UK. Manganese deficiency occurs more commonly in cereals, with winter cereals less susceptible to drought-induced deficiencies than spring cereals as their root structure is better developed, allowing them to better exploit micronutrients from within the soil profile.
Manganese deficiency had been observed in all parts of the UK, though often occurring only in patches in fields; however, incidence of the deficiency could be associated with and, therefore, anticipated on a number of geological formations and soil types. Moderate to severe Manganese deficiency in arable crops usually only occurs on: Organic, peaty and marshland soils with soil pH over 6.0, especially over 6.5; • Sandy soils (sand, loamy sand) with soil pH over 6.5, especially over 7.0. Manganese deficiency is usually induced by low availability of soil Manganese for crop uptake, rather than being due to an absolute shortage of soil Manganese. Field conditions most often associated with Manganese deficiency in the UK are: high soil pH; high organic matter content; poor root development; poor root-soil contact in under-consolidated (fluffy) seedbeds; low soil temperatures; and below average rainfall. The overall combination of these factors will dictate the severity of the deficiency in crops when it occurs. The higher the organic matter content, the lower the soil pH needs to be to prevent deficiency occurring. A temporary shortage of Manganese is also often induced under poor soil physical conditions, especially after periods of cold, dry weather which put a poorly rooted crop under stress.
