Diagnosing sulphur deficiency in narrow-leafed lupins
Lupin crops have not yet shown sulphur (S) deficiency in Western Australia, however S deficiency can cause production losses, with legumes being more sensitive.
What to look for
- Smaller paler plants.
- Deficiency is most likely in cold wet conditions on deep pale sands.
- Growth and colour are affected simultaneously.
- The whole plant becomes pale but middle leaves are affected last.
- New leaves and new growth become very pale green and clumpy due to increasingly miniature leaves with spiky-tipped leaflets.
- Older leaf leaflets drop, and have total or mottled chlorosis.
What else could it be
|Diagnosing zinc deficiency in narrow-leafed lupins||Pale clumpy new growth||Dark leaf lesions|
|Diagnosing group B herbicide damage in narrow-leafed lupins||Stunted plants with pale new leaves||Necrotic growing point and new leaves|
|Diagnosing iron deficiency in narrow-leafed lupins||Stunted plants with pale new leaves||Mostly on limed or wet soils|
Where does it occur?
- Sulphur leaches in high rainfall on sandy acidic soils.
- Cold, wet conditions slow sulphur mineralisation and plant uptake.
- Soil S reserves occur as a component of organic matter, and sulphate adsorbed on to clay and iron and aluminium oxides.
- Root restricting constraints such as traffic pans, disease or soil acidity will worsen S deficiency.
- In areas close to the sea or industrial pollution, there can be significant input of S from the atmosphere.
- Unnecessary as other crops require S before it is a problem in narrow-leafed lupins.
How can it be monitored?
- Critical S concentrations are 0.28% (young leaves), 0.07% (stems), and 0.15% (whole shoots).
- The critical N:S ratio for S deficiency is 15.
- 0-10cm soil test is a poor guide for sulphur, as plants can access S reserves at depth.
Page last updated: Wednesday, 6 May 2015 - 11:18am