Spotlight on Manganese Deficiency in Spring Cereals
16 May 2025Manganese (Mn) deficiency is particularly common in spring barley and can lead to yield losses if left untreated. Soil applications of Mn are generally ineffective, as the applied Mn rapidly changes into less available forms. Deficiencies are best prevented or, where Mn deficiency only occurs infrequently, corrected by foliar sprays with Mn each year.
The Mn content of plants varies greatly, usually from trace up to 500 mg/kg DM, depending on soil Mn availability. Much larger, toxic concentrations can occur in plants growing on very acidic soils. Plant Mn concentrations decrease significantly with increasing pH value. Typical Mn offtakes in cereal grain and straw at harvest are typically in the region of 26g and 40g per tonne (fresh material) respectively.
The most characteristic symptom of Mn deficiency is leaf interveinal chlorosis, which can quickly develop in affected crops. The deficiency also shows as a general paling of leaves which can go unnoticed or be confused with other agronomic problems such as poor drainage conditions. In cereals, deficiency symptoms usually first appear in spring as patches of pale green, limp growth which, if left untreated, leads to general plant stunting and species-specific leaf spotting as seen in spring barley.
All leaves are affected, starting with the oldest ones. Symptoms can appear at any time from about the third leaf stage until flag leaf emergence, depending on the season. Unconsolidated areas show the most pronounced symptoms, contrasting with wheeling areas standing out as greener lines within the field.
Diagnosis of Mn deficiency is usually made on recognition of visible symptoms and knowledge of the soil characteristics and field history, backed up by plant analysis. A critical leaf Mn content of 20 ppm (100% DM) is used to diagnose deficiency in all crops, including cereals, oilseed rape and horticultural crops.
| Plant Mn conc (ppm) | Soil status | Yield response |
|---|---|---|
| <20 | deficiency | yield response likely |
| 20-30 | low | yield response possible |
| 30-40 | satisfactory | yield response unlikely |
| >40 | well supplied | no yield response |
Plant analysis should ideally be carried out early in the growing season when the plants are young. Interpretation of the results is easier, and this also allows sufficient time for foliar nutrient sprays to be applied to overcome any deficiency.
Foliar spraying with Mn is the recommended method for effective control or treatment of Mn deficiency. Foliar Mn sprays should be applied in the spring when deficiency symptoms are first identified, provided there is sufficient leaf cover for Mn uptake at that stage, otherwise routinely during late tillering to early stem extension (GS24-31) on fields with a known history of moderate to severe Mn deficiency problems in most years. A Mn spray application is not, however, normally considered worthwhile beyond ear emergence stage, where a deficiency is identified late in the season. Where severe Mn deficiency occurs, 2 or 3 sprays may be necessary.
Manganese sulphate as a remedy can be difficult to dissolve, it’s not compatible with many other agrochemicals for tank mixing and can cause leaf scorch, especially on a stressed crop. Chelated products have advantages of much greater compatibility with other agrochemicals, better solubility and no risk of crop scorch but supply less Mn and are more expensive. Chelated products are however equally effective as manganese sulphate, if supplied in sufficient quantity. Seed treatments or coatings can be used and while these provide Manganese near the seed, they need to be followed up by a foliar application.
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