Gypsum composition is calcium sulphate, gypsum makes those nutrients more available to plants than other common sources of these nutrients.

Calcium affects mineral uptake and is one of the first nutrients to be balanced in the soil. Calcium is important as it governs cell wall strength, plant resilience as well as plant growth, fruit quality and storage.  Good fruit quality requires adequate amounts of calcium constantly available to plant roots throughout the season. Sulphur is part of an enzyme used in metabolising nitrates and in the production of quality proteins in plants. (The Biological Farmer, Gary Zimmer, 2017)

“Incorporating annual gypsum applications in fertiliser programmes aids to increase soil porosity, soil aeration and drainage. Healthy roots are important too for good leaf size in early spring and to size new fruit from late spring onwards.”, says Lindsay Heard of Brenmark Horticultural Consultants.

Learning from Soil Science around the world

The physical improvements gypsum can make to soil structure, particularly drainage and aeration, will assist in reducing the severity and incidence of Phytophthora infections or root rot diseases particularly in avocados.

The Soil Science Society of America noted gypsum is a moderately-soluble mineral so the calcium can move further down the soil profile. The calcium in gypsum increases the precipitation of aluminium and inhibits aluminium uptake by plant roots in acid soils,  promoting deeper rooting plants. When roots are more abundant and can grow deeper into the soil profile, they can take up more water and nutrients, even during the drier periods of a growing season.

Gypsum is called the clay breaker as the sulphate bonds with excess magnesium in the soil, creating magnesium sulphate, which is easily leached from the root profile. With the correct ratios of magnesium, calcium and potassium will allow soils to breathe and increase water infiltration and drainage through the soil profile. (Nutritech Australia Soil Therapy Guidelines, Part 3, 2017)

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 around 3%- 5%.  This will depend on soil type, as a clay soil can hold higher levels of calcium than a sandy soil, and your fruit crop. Talk to your advisor for further information and guidance.

And as Lindsay Heard comments “I have been formulating fertiliser programmes for avocados for more than 20 years and for kiwifruit for more than 30 years and have observed increased growth rates following good maintenance gypsum applications in young avocado blocks”.

Gypsum has multiple benefits in orchard situations and is BioGro certified.