Sulphur (S) deficiency is rare in Western Australia as field peas are generally grown on heavy-textured soils.
What to look for
Paddock
Smaller plants with pale new growth.
Deficiency is most likely in cold wet conditions on deep pale sands.
Plant
Growth and colour are affected simultaneously.
New leaves and tendrils become evenly chlorotic.
Randomly distributed light brown chlorotic spots develop on chlorotic leaves of severely deficient plants.
Where does it occur?
Soil type
S leaches in high rainfall on sandy acidic soils.
Cold, wet conditions slow sulphur mineralisation and plant uptake.
S is as a component of organic matter, and sulphate is adsorbed on to clay, 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
Top-dressing S sources such as gypsum will correct the deficiency
Foliar sprays generally cannot supply enough S to overcome a severe deficiency.
Grain S removal (1.8 kg per tonne of grain), is a guide to long term requirements.
Deeper soil testing may eliminate costly S fertiliser application.
Root restricting constraints such as traffic pans, disease or soil acidity will worsen S deficiency and final yield, even if S is available further down the soil profile.
How can it be monitored?
Soil test
Australian laboratory standards have not been established for field peas. A guide from literature for the top half of a shoot is 0.2%. Sample paired good and poor plants at the same growth stage.
0-10cm soil test (Blair S test in WA) is a poor guide for S, as plants can access S reserves at depth.
