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.

 

Growth and colour are affected simultaneously
New leaves and new growth become very pale green and clumpy
Uniformly pale and increasingly miniature leaves with spiky-tipped leaflets
Older leaf leaflets drop, and have total or mottled chlorosis

What to look for

    Paddock

  • Smaller paler plants.
  • Deficiency is most likely in cold wet conditions on deep pale sands.

    Plant

  • 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

Condition Similarities Differences
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?

Soil type
Soil type
Wet conditions
Wet conditions
  • 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.

Management strategies

  • Unnecessary as other crops require S before it is a problem in narrow-leafed lupins.

How can it be monitored?

Tissue test
Tissue test
Soil test
Soil test
  • 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.

Further information

Where to go for expert help

Page last updated: Wednesday, 6 May 2015 - 11:18am