Gypsum is a natural mineral that is good source of calcium and sulphur which can be used to improve physical and chemical properties of soil as well as support crop nutrition.

Situations that will benefit from applications of gypsum include³;

1. A crop has an identified need for sulfur, eg,onions and brassicas.
2. A crop has an identified need for calcium, eg potato, tomato or peppers.
3. Aluminium toxicity in acidic subsoils
4. Saline or sodic soils
5. Phosphorus run off from productive land

Gypsum adds soluble calcium and sulphur to the soil

Gypsum is an excellent source of calcium and sulphur for plant nutrition as well as for improving crop yield.

Plants require additional calcium and sulphur during crop establishment, active periods of growth as well as during flowering and fruit set. Calcium is used to increase cell wall strength which helps protect plants against diseases and also helps stimulate root growth.

Sulphur is bound to organic matter in the soil, soils with low organic matter will benefit from additional sulphur applications. Sulphur is an important mineral and is used in plants for many processes including protein and amino acid formation.

Gypsum adds calcium to the soil more quickly than lime because it is more soluble than an agricultural lime.  Applying gypsum can increase the amount of soluble calcium in the soil solution. An increase in sulphur concentration in soil and crop biomass is frequently observed after gypsum applications².

Gypsum relieves aluminium toxicity

Aluminium toxicity around plant roots typically occurs in soils lower than pH 4.5 where the aluminium becomes soluble in the soil solution, noticeably in the subsoil layer. Gypsum can relieve aluminium toxicity, where calcium replaces aluminium on the soil colloid, increasing aluminium absorption and removal from the soil solution².  This benefits crops as it makes it possible for deeper rooting plants which can access nutrients and water at greater depth in the soil.

Gypsum improves saline or sodic soils¹ ²

Sodic soils have excess sodium on soil colloid exchange sites that causes soil dispersion ( lack of soil aggregate structure) and water infiltration issues.¹ When gypsum is applied to sodic soils, the calcium ions displace sodium on soil colloid and irrigation water flush it below the root zone. Sodium removal improves soil particle aggregation, soil structure and water infiltration. In addition, the soil is less prone to compaction.

Gypsum can decrease phosphorus runoff from productive soil.²

The calcium ions in Gypsum can increase precipitation and adsorption of phosphate ions and organic matter into soil particles. Gypsum has been reported to halve the phosphorus losses in some conditions. 4

Gypsum can also improve soil aggregation, through flocculation of the fine soil particles, as well as leaching excess sodium. This improves water infiltration into the soil and reduces surface runoff. Improved stability of soil aggregates reduces the potential loss of soil particles to waterways. 

Gypsum has many benefits to support and improve soil structure as well as crop nutrition. Talk to your local fertiliser advisor or rep about the benefits of applying gypsum for your crop.

Gypsum, supporting soil and plant health.

References

1. Response of Soils and Crops to Gypsum Application in Ohio

2. Farm Progress: Does Gypsum Improve Soil Health?

3. US Dept Agriculture: Amending Soils with Lime or Gypsum (NRCS 333) AgBMPs

4. Tim A Jenkins, Vesna Jenkins, NZ Use of Gypsum to Reduce Effluent and Fertiliser Nutrient Loss To Waterways.