The Role of Calcium and Sulphur in Plants
/ by Winstone Gypsum
Soil is a major source of nutrients required by plants for growth, the three main nutrients include nitrogen, phosphorus and potassium. Plants also need small quantities of iron, manganese, zinc, copper, boron and molybdenum. ³
Other important nutrients include calcium, magnesium and sulphur.³ Let’s delve into why calcium and sulphur are needed for plant growth in more detail.
Role of Calcium in Plants
Calcium is involved in many plant processes, including root health, growth of new roots and root hairs, cell integrity, cell elongation and division, germination, pollen growth, and senescence ¹ ².
Calcium is taken up by the plant via the roots, with the area just behind the tips of a growing root capable of calcium uptake (unlike potassium and phosphorus), so factors inhibiting root growth also inhibit its uptake. Calcium is transported through the plant exclusively in the xylem.¹
More than 35 calcium-related disorders have been identified in fruits and vegetables. These disorders often develop due to poor root growth rather than because of inadequate calcium supplies.¹ Once calcium is deposited in plant tissue it is immobile, as a result calcium deficiency symptoms appear first in young tissues.
Well known sources of calcium include agricultural lime, gypsum, dolomite and superphosphate (a mixture of calcium phosphate and calcium sulphate). ²
The role of sulphur in plants
Sulphur is responsible for many flavour and odour compounds in plants, for example the aroma of onions and cabbage. Sulphur is a constituent of amino acids, such as cysteine and methionine, as well as in certain enzymes, vitamins, and oils. Sulphur is also involved in energy-producing processes in plants ¹, ².
The most abundant reservoir of sulphur is in the form of lipids, amino acids, and proteins in the soil which are broken down by soil microorganisms into inorganic sulphates. Sulphur deficiency is not a problem in soils high in organic matter, but sulphur does leach easily. ²
At any given time, a substantial amount of the total sulphur exists in the sulphate form, which is readily available to plants and actively taken up by the roots.¹
Sulphate is highly mobile in the soil and reaches the plant roots quickly. The application of sulphate sulphur during establishment and intensive plant growth makes it suitable for combination with other fertilisers, especially nitrogen.
Sulphur's uptake and availability is not influenced by soil pH and can be taken up by plants readily over a range of soil conditions. In a plant, once sulphur is incorporated into amino acid molecules, it is not easily mobilized within the plant. Deficiency symptoms, therefore, occur in young tissues before older ones.¹
Fertilisers such as superphosphate, gypsum, elemental sulphur and sulphate of ammonia are the main sources of sulphur.² Gypsum supplies sulphate sulphur in a plant available form which is immediately available and easily absorbed by plants.
Elemental sulphur, needs to be oxidized to sulphate by soil microbes, which takes time. Also, elemental sulphur has a strong acidifying effect on the soil. ³
Gypsum as a supplementary calcium and sulphur source
Gypsum supplies 23% calcium and 18% sulphur in a plant available form and is considered moderately soluble so plants are able to access these nutrients easily.
To ensure good availability with a supply of calcium and sulphate sulphur during high demand periods of plant growth, such as at plant establishment, flowering and fruit set, it is advisable to include gypsum into your fertiliser programme.
For more information on gypsum as an available source of calcium and sulphur for your crop, please contact your local fertiliser advisor.
Gypsum is Bio Gro certified. Gypsum supports plant and soil health.
References
1. Peaches, plums and nectarines mineral nutrition technical guide, R Scott Johnson and K Uriu