Polyhalite: The smart and natural choice to feed grass

Exclusive to ICL, polyhalite is a mineral containing four essential nutrients: potassium, magnesium, calcium and sulfur. It is an integral component of ICL’s Gronamic line, containing high-quality organic-based fertilisers, and ProTurf, the category-leading outfield blended fertiliser range.

In this article:

• A smart mineral discovered
• Why is polyhalite useful as a nutrient source?
• Polyhalite for sports turf and landscapes
• Composition
• Benefits

How ICL discovered that polyhalite could be a valuable component when used in fertilisers is an interesting story. Following worldwide successes with crops, polyhalite was found to deliver great results for turfgrass compared with standard nutrient fertilisers.

A smart mineral discovered

Polyhalite is a natural, sulphate-based mineral formed during the evaporation of prehistoric seas millions of years ago and is present underneath the North Sea close to the UK coast. As the name suggests—poly (more than one) halite (salt)—it’s a complex crystal containing four minerals: sulfur, potassium, magnesium, and calcium.

ICL owns and operates the only polyhalite mine in the world, located in the north of England. Estimated to have a billion tons of polyhalite in reserve, the Cleveland Potash mine extracts potassium for use in fertilisers that improve water retention, yield, nutrient value, color, texture, and disease resistance, especially in food crops.

In potassium mining the drilling goes deep down through a seam of polyhalite. When first extracted during the mining process, it was seen merely as waste, a byproduct, and disposed of. But committed to minimizing waste and improving the carbon footprint, ICL re-evaluated polyhalite, as it does with all byproducts occurring as a result of extraction processes. In 2010 the first polyhalite samples were brought to the surface of the mine from a depth of 1,200 meters. ICL’s researchers began to explore whether there was any value at all in the extracted material. And what they discovered was that polyhalite was not simply waste material—it was a valuable mineral source of four macronutrients.

Why is polyhalite useful as a nutrient source?

To grow and function well, turfgrass needs a balance of nitrogen and other key macronutrients. Potassium is essential for turfgrass health and stress tolerance, calcium for cell division and strong cell walls, magnesium for photosynthesis and sulphur for protein synthesis. This brings polyhalite into the picture. It provides all four essential macronutrients required by a grass plant alongside applications of nitrogen and phosphorus.

Much of the independent trial work with polyhalite has been completed on field crops where including it in blended fertilisers resulted in higher yields, better rooting, and higher uptake of nutrients overall. Trials confirmed that polyhalite not only offered nutritional benefits but also that the natural process by which it was produced made it a low carbon footprint fertiliser too. Polyhalite is available in its natural state. It is mined, crushed, screened, and bagged and does not involve any chemical separation or other industrial process, unlike most other blended compound fertilisers. The very low content of chloride, for example, makes it ideal for use on chloride-sensitive crops. Polysulphate is also approved for organic agriculture and is Soil Association certified, which helps growers achieve carbon targets and certifications demanded by retailers and food processors.

Relative nutrient uptake from Polysulphate compared with equivalent standard nutrient sources and unfertilised control.

Polyhalite for sports turf and landscapes

ICL introduced polyhalite into ProTurf blends, combining controlled-release fertiliser technology, urea, and compound fertiliser. The result is healthy, even growth without surges. The turf responds quickly even in cooler growing conditions and including magnesium significantly improves turf colour. In ICL’s Gronamic range, the polyhalite mineral is mixed with organic sources, combining the best that minerals and organics have to offer in each granule.

Dr. Andy Owen, International Technical Manager for Turf & Amenity at ICL explains: “Independent trials have shown that polyhalite provides Ca, Mg, and K in forms that are readily available to the grass plant. The relative uptake of nutrients from polyhalite by turf was found to be as good, if not better, than standard forms of nutrient fertilisers. It ensures that essential macronutrients are available to maintain healthy turf and reduces the possibility of nutrient deficiency. In user trials we’ve seen ProTurf products provide great turf density and resilience, a very even green-up, and a response that lasts a long time, at a very acceptable price point.”

If you’re looking for a fertiliser that offers better value and low environmental impact, ICL blends with polyhalite, such as Gronamic and ProTurf, could be a very smart move.

It is suitable for application through the growing season on football pitches, golf fairways, golf tees, in landscaping, and in gardens.

Composition

K₂Ca₂Mg (SO₄)4 • 2(H₂O)

48%     SO₃ as sulphate

14%     K₂O as from sulphate of potash

6%       MgO as from magnesium sulphate

17%     CaO as from calcium sulphate

Less than 3% chloride

Benefits

• European source
• Low carbon footprint
• Environmentally benign—used in its natural state
• No processing or waste product
• Non-acidifying
• Secure supply