Diagnosing manganese deficiency in wheat
Manganese deficiency in wheat is widespread but confined to small soil related patches that have declined as soils have acidified.
What to look for
- Manganese deficiency often appears as patches of pale, floppy wheat in an otherwise green healthy crop.
- Frequently plants are stunted and occur in distinct patches.
- Initially, middle leaves are affected first, but it can be difficult to determine which leaves are most affected as symptoms rapidly spread to other leaves and the growing point.
- Leaves develop interveinal chlorosis and/ or white necrotic flecks and blotches.
- Leaves often kink, collapse and eventually die.
- Tillering is reduced, with extensive leaf and tiller death. With extended deficiency, the plant may die.
- Surviving plants produce fewer and smaller heads.
What else could it be
|Diagnosing zinc deficiency in wheat||Pale plants with interveinal chlorosis and kinked leaves||Differences include linear 'tramline' necrosis on zinc deficient plants. Manganese deficient plants are more yellow and wilted|
|Diagnosing nitrogen deficiency in wheat||Pale plants||Nitrogen deficient plants do not show wilting, interveinal chlorosis, leaf kinking and death|
|Diagnosing waterlogging in cereals||Pale plants||Waterlogged plants do not show wilting, interveinal chlorosis, leaf kinking and death|
|Diagnosing iron deficiency in cereals||Pale plants||New leaves are affected first and plants do not die|
|Diagnosing sulphur deficiency in cereals||Pale plants||New leaves are affected first and plants do not die|
Where does it occur?
- Deficiency tends to occur on coastal alkaline soils and high phosphorus retention index (PRI), water repellent gravels associated with wandoo powderbark wandoo, brown and blue mallet and blue mallee vegetation.
- This occurs in an area south of Moora to Katanning and east from Corrigin to Dumbleyung, and infrequently on the Esperance sandplain and mallee area north of Esperance.
- Manganese deficiency is exacerbated by dry soil, high soil pH, alkaline fertilisers and root pruning herbicides (particularly groups A and B).
- Foliar spray.
- Acidifying ammonium nitrogen fertilisers can reduce manganese deficiency by lowering pH and making manganese more available to growing crops.
- Manganese fertiliser is effective but expensive as high rates and several applications are required to generate residual value.
- Seed manganese coating treatments have little effect in correcting the deficiency.
How can it be monitored?
- A whole-top plant test of 17 milligrams per kilogram (mg/kg) gives a rough indication of deficiency.
- Use youngest emerged blade test for accurate manganese levels,with levels less than 15 parts per million (ppm) an indicator of manganese deficiency.
- Compare paired good/poor plant samples where possible.
- There is no reliable soil test for manganese in cereals. As soil test manganese is generally poorly related to grain yield increase, a critical concentrations can't be determined.
Where to go for expert help
Page last updated: Thursday, 20 July 2017 - 1:37pm