Gypsum is well known as the “clay breaker” for improving soil structure in clay soils. Often gypsum’s other benefits are overlooked. Due to its many features, gypsum is a true multi tasker that can support healthy crop establishment and plant growth by improving soil structure, aeration and water infiltration.

New Zealand soils are known to be sulphur deficient. Gypsum is an excellent source of calcium and sulphur for plant nutrition and for improving crop yield.  As an economical, low cost option gypsum supplies 18% sulphur and 23% calcium.

Calcium is an essential nutrient, affecting mineral uptake and is one of the priority nutrients to be balanced in the soil. Having good levels of calcium is important as it governs cell wall strength, plant resilience as well as plant growth and crop quality.   Sulphur is part of an enzyme used in metabolising nitrates and in the production of quality proteins.

Soil Science Society of America mentions gypsum makes calcium and sulphur nutrients more available to plants than other common sources of these nutrients.  Finely ground gypsum particles are small and uniform in size making them quite reactive. This can be a real benefit. 

Used as a clay breaker,  the sulphate in gypsum bonds with excess magnesium in the soil  creating magnesium sulphate which is very easily leached from the root profile. With the correct ratios of magnesium, calcium and potassium this will allow soils to breathe and increase water infiltration and drainage through the soil profile. (1)

Research on crops of maize and wheat has shown gypsum applied at 1000kgs/ Ha with the recommended application of nitrogen fertiliser, improves maize yields. (2).

Gypsum benefits soil structure

Gypsum has been used for many years to improve soil particle aggregation and porosity in clay soils and in areas where there is compaction, adverse surface water pooling and drainage issues.

Gypsum top dressed after sowing maize can decrease and prevent crust formation on the soil surface which results from rain drops or from sprinkler irrigation on unstable soil. Prevention of crust formation means greater seed emergence, more rapid seed emergence and establishment (3).

As a moderately-soluble mineral (3), surface applied gypsum leaches down to the subsoil where it increases the precipitation of aluminium in acid soils, inhibiting aluminium uptake and promoting deeper rooting of plants. When roots are more abundant and can grow deeper into the soil profile, they take up more water and nutrients, even during the drier periods of a growing season.

Gypsum also reduces phosphorus movement out of the field into waterways (3).

Unsure of your calcium levels? 

You can refer to the percent  base saturation on your soil lab test report, as a rough guide calcium should be between 60% - 80%, Magnesium 10% - 20% and potassium 3% - 5%.  This will depend on soil type, a clay soil can hold higher levels of calcium than a sandy soil. Talk to your fertiliser advisor for further information and guidance.

Gypsum is Bio Gro certified.

1. Nutritech Australia Soil Therapy Guidelines Part 3, 2017
2. Use of gypsum to increase fertiliser efficiency on normal soils, Science Alert, Asian Journal, 10.3923/ajps.2003.673.676
3. Soil Science Society of America, Gypsum as an Agricultural product, USA, Bulletin 945