Mobility within tree: Low

Uptake Form: Mn²⁺

Function: Hill reaction photosynthesis II

Deficiency/Toxicity Symptoms:  Manganese is required in the Hill reaction of photosystem II and is important for enzyme activation (Maher 2004).  Manganese deficiencies are not found in soils with acidic or neutral pH. High soil alkalinity and high organic matter levels promote occurrence of Mn deficiency. Manganese deficiency results in chlorosis between main veins starting at the margins and extending to the midrib similar to Fe and Mg deficiencies.  However, chlorosis does not appear in the very youngest leaves, veins do not stay green as seen in Fe deficiency and interveinal necrosis is not seen as for Mg deficiency.  Manganese deficiency develops in younger leaves after they have fully expanded.  In peach, terminal growth may be stunted. Manganese excess is partly responsible for “measles” in apples particularly in ‘Delicious’ and ‘Jonathan” cultivars.  Low Ca and B are also involved as previously mentioned.

Manganese (Mn) Sources and Application

            Manganese sprays may be combined with sprays of B, zinc chelate, Mg or urea.  Dilute application is not recommended. Table 1 is summarized Mn foliar application rates.

Table 1. Possible Manganese foliar application rates