Field Research & Agronomy

Sulphur is an essential plant nutrient. It’s required for the production of amino acids, which make up the proteins critical to plant growth. Sulphur deficiency can significantly reduce yield in pastures on sandy soils in wet years, when the sulphate form of sulphur leaches below the root zone of pasture plants.

Role of sulphur in soils

Varying degrees of sulphur are present in nearly all soils. Clay and gravel soils generally have more sulphur present, which is due in part to the composition of the original parent rock. Organic sulphur, which is mineralised into plant-available sulphate sulphur, is more prevalent in soils with high clay and gravel content. Sandier soils from higher rainfall areas do not have any ability to restrict the leaching of water-soluble sulphate sulphur.

As demonstrated in this nutrient removal table, sulphur remaining in plant residues is readily recycled into the soil.

Sulphur Deficiency

Cereals: Sulphur deficiency symptoms in cereals will often resemble nitrogen deficiency with pale green/yellow leaves. To determine the cause of the deficiency, closely inspect the plant. In sulphur deficient plants, the youngest leaves will turn yellow, unlike nitrogen deficiency which affects the oldest leaves.

Clover Plants: Similar symptoms are present in clover plants in that yellow leaves are present. In severe cases, the leaves will stand upright with a ‘cupped’ appearance.

Canola Plants: These plants have a high requirement for sulphur. When deficient, the leaves will ‘curl’, turn yellow and the veins will show a marked red/purple colouration.

Preventing Sulphur Deficiencies

Modern, high analysis fertilizers such as MAPSZC and DAPSZC can supply sufficient levels of sulphur to cereal crops. Canola crops will require more than can be safely or conveniently applied using a seeding fertilizer. As such, extra sulphur must be applied either before seeding (gypsum), or post seeding (Amsul).

If a deficiency manifests in an established crop, this can be easily corrected with an application of sulphate of ammonia.

Supplies of Sulphur

Sulphate Sulphur

• Immediately available to the plant
• Water soluble
• Quick acting
• Leachable
• Can be lost with one heavy rainfall event

Elemental Sulphur

• Sustained release
• Not lost by leaching
• More available when maximum plant growth occurs in spring
• Will build up a sulphur ‘bank’
• Slow to break down
• Not suitable to correct a visual deficiency in plants

To find out more about preventing or correcting a sulphur deficiency, speak to your local Area Manager.