What it does
Manganese deficiency affects photosynthesis and protein synthesis. Mn-deficient plants are often deficient in Phosphorus.
Why and where it occurs
Manganese deficiency is relatively rare especially in irrigated rice systems.
Mn deficiency occurs frequently in upland rice, but is uncommon in rainfed or lowland rice because the solubility of Mn increases under submerged conditions.
Soils particularly prone to Mn deficiency include the following types:
- acid upland soils (Ultisols, Oxisols)
- alkaline and calcareous soils with low organic matter status and small amounts of reducible Mn
- degraded paddy soils containing large amounts of active Fe
- leached sandy soils containing small amounts of Mn
- leached, old acid sulfate soils with low base content
- alkaline and calcareous organic soils (Histosols)
- highly weathered soils with low total Mn content
How to identify
Check for the following symptoms:
- Pale grayish green interveinal chlorosis spreads from the tip to the leaf base
- Necrotic brown spots develop later and leaf becomes dark brown
- Newly emerging leaves short, narrow, and light green
- Deficient plants shorter, with fewer leaves, weigh less, and smaller root system at tillering
- Plants stunted but tillering is not affected
- Affected plants more susceptible to brown spot (caused by Helminthosporium oryzae)
- Mn-deficient rice plants often deficient in P
In soils where both Mn deficiency and Fe toxicity occur, Mn-deficient rice plants contain a large concentration of Fe, and may also show symptoms of bronzing
Click on images to enlarge
How to manage
Where possible, the general management options for Mn deficiency are:
- Apply farmyard manure or straw (incorporated or burned) to balance Mn removal and enhance Mn(IV) reduction in soils containing small amounts of Mn and low organic matter status.
- Use acid-forming fertilizers, e.g., ammonia sulfate [(NH4)2SO4] instead of urea.
Learn more
View full fact sheet: Manganese deficiency on IRRI Rice Knowledge Bank