SOYL Reports Back from Potash Mine 

10 November 2010

SOYL's Northern regional manager, Aidan Monaghan, recently took a study tour to Germany to discover how potash fertiliser is derived.  Potassium is a major nutrient required for plant growth and is usually applied as potassium chloride, known as muriate of potash or simply ‘MOP’.  The tour was organised with K+S UK & Eire Ltd, the UK subsidiary of K+S KALI GmbH, one of the major global producers of potash and magnesium fertilisers.

Potash was formed in seams deep underground by layers of deposits from shallow seas which evaporated and then were flooded and evaporated again, and so on.  Seams in Germany were formed some 200 million years ago and manipulated over time by the movement of tectonic plates and volcanic activity.  Unique to the German potash mines is the presence of the valuable natural mineral, Kieserite (magnesium sulphate).  This allows K+S KALI to produce not only straight potash and magnesium fertilisers, but also balanced products with potash, magnesium and sulphur which are more tailored to crop requirements

The reddish deposits in the centre are those of interest – typically in 1-3m layers (see image below).

Potash seams

The seams of interest for agricultural fertiliser lie approximately 500-1500 metres underground.  The mine is accessed by lift shafts which take you down from the Earth's surface to 507m underground in about 90 seconds. The mine has then been formed by tunnels cut into the deposits leaving pillars between of approximately 30m square.  Merkers Mine is one of the oldest in the world with work starting in 1911 – there are now 4600 km of roadways and tunnels where deposits have been removed.  Our trip took us on a 22 km tour throughout the mine showing the history and process of mining.  It also took us to the deepest bar in the world at 800m below ground (see image below), where German beer was of course served!

Merkers Mine bar at over 800m below ground

Once the crude salt has been brought to the surface it is put into solution.  The valuable mineral elements are then re-crystallised after a series of purification steps involving floatation, centrifugation, electrostatic separation etc. and finally compacted and granulated to form the final potash and magnesium fertilisers used on farm.  In this way, a range of products are formed including 60er Kali (MOP), KALISOP (SOP), Korn-Kali, Patentkali, ESTA Kieserite and even foliar bittersalz (EPSO Top).  The products are then transported by rail,  road and sea to both Europe and overseas where they are used in agriculture.

Merkers Mine is also famous for its role in the Second World War.  Hitler used the mine to hoard gold, silver, bank notes and art.  As the Germans retreated, the American army discovered approximately 200 tonnes of gold, a large quantity of silver, 3 billion in German bank notes and several complete galleries of art.

K+S KALI GmbH website >