A new fertilizer, high in sulphate

Polysulphate is a new fertilizer, high in sulphate, available in its natural state, and mined in the UK

A unique benefit is its additional natural content of other macronutrients. Polysulphate™ fertilizer comes from the polyhalite layer of rock, over 1000m below the North Sea off the North Yorkshire coast in the UK. Deposited 260 million years ago, it lies 150-170m below the potash seam at the Cleveland Potash Boulby Mine.

The main polyhalite seam was reached in September 2010, bringing the first samples up to the surface. It is estimated there are one billion tonnes available from this one source.

Polysulphate (the trade name for this polyhalite fertilizer) is available as both a granular and powder product. The 2-4mm granular product has excellent spreading characteristics and is an ideal fertilizer to apply alongside straight nitrogen.

Boulby mine stratigraphy showing where polyhalite is found

Polysulphate contains

  • 48% SO3 as sulphate
  • 14% K2O as from sulphate of potash
  • 6% MgO as from magnesium sulphate
  • 17% CaO as from calcium sulphate

Benefits of potassium, magnesium and calcium

In addition to sulphate, Polysulphate has the added bonus of valuable levels of potassium (K2O), magnesium (MgO) and calcium (CaO).

Potash is recognised as a necessary regular input, with recommendations based on soil indices and removal at harvest. But surveys have shown reserves are dropping, with more arable soils at index 0 or 1. Most of the potassium in a harvested crop of cereals is in the straw. So when selling straw makes commercial sense, it’s important to boost potassium inputs to compensate. The potassium in Polysulphate complements routine fertilizer applications.

Magnesium is often only applied to some cash crops and vegetables. This macronutrient is part of the chlorophyll in all green plants and essential for photosynthesis. It is removed in significant quantities at harvest of all crops, and an application from Polysulphate will provide a useful input of a nutrient that is frequently overlooked.

The fourth constituent of Polysulphate is calcium, which means that it has effectively no non-nutrient constituents. Calcium is responsible for proper plant cell division and for strengthening cell walls. Polysulphate helps to maintain essential calcium reserves in the soil.

Polysulphate is particularly suitable for crops which prefer low levels of chloride in the soil, such as tobacco, grapes and other fruits, and where higher dry-matters are desired in potatoes.