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Maximum Units per 1 tonne
TNV ..... 58
CaCO3 ..... 72%
AL203 ..... 1.5%
B ..... 700ppm
Ca0 ..... 49.6%
CL ..... 1.75%
Fe0 ..... 15.2%
K20 ..... 0.03%
Mg0 ..... 7.9%
Mn0 ..... 3.6%
P205 ..... 1.8%
Zn ..... 126ppm
Cu ..... 137ppm
Mo ..... 45ppm
Co ..... 4ppm
So3 ..... 0.3%


These samples were analysed by various laboratories from steel works slag from South Wales.

Steel Works Slag

Steel works slag is a by-product of the basic oxygen stele making process used by British Steel at their Llanwern, Port Talbot, Scunthorpe and Teeside works.

Like the old basic slag our grade of steel works slag called Super Slag Basic is principally a lime based material which has absorbed the oxides and trace elements arising from the refining of iron. Although it contains less phosphates than the old basic slag. Super Slag Basic produces a high phosphate response in the soil owing to its soil conditioning properties. Field trials and practical experiences have shown that steel works slag performs exceptionally with significant improvements in crop yield and pasture quality.

Super Slag Basic has similar neutralising properties to that of ground limestone and is applied to the land at a similar rate, appropriate to its pH level. At the maximum recommended rate of 1.5 tonnes/acre, it provides around 60 units of available phosphate together with magnesium, iron, manganese, sulphur and a wide range of trace elements essential for healthy crops and animal wellbeing.

On spreading, Super Slag Basic acts in four ways. It provides:-

  • a readily available source of phosphate
  • an effective source of lime
  • a source of essential trace elements
  • a release mechanism for locked up phosphates.

Super Slag Basic is crushed down to a size that is agronomically effective. It is safe to handle and easy to spread and is prepared to 4 ml to dust particle size. This size gives the optimum release of nutrients whilst enabling ease of handling and spreading.

The remarkable performances of steel works slag has been established through extensive field study trials carried out by Newcastle University. Increases in dry matter yield were recorded over a three year period for Cockle Park (soil pH=5.4) and New Deanham (soil pH=4.8).

Slag spread at 1.6 tonne/acre. Limestone spread at same neutralising level as slag. TSP spread at same phosphate level as slag. Yield increase with slag over 3 times that of limestone of TSP at Cockle Park and more than double at New Deanham.

The herbage uptake of P205 was measured at Cockle Park where steel work slag again performed exceptionally well.

P2O5 Applied
P2O5 Taken up
Uptake of P2O5 Applied
SuperSlag Basic

Increase in uptake of P2O5 with steel works slag over 50% more than with TSP and three times more than with gafsa.

Basic slag was thought by many to be the best grassland fertiliser ever. Super Slag Basic is its modern day equivalent, rich in calcium, magnesium, phosphate, sulphur and essential trace elements.

Super Slag Basic is good for your land; it replaces the trace elements and minerals which basic slag used to provide. It gives substantial increases in crop yields, sweetens pastures and is beneficial to grazing livestock.

What value do you get when you use Super Slag Basic ?
When applied at the usual rate of 1 mt/ac you get:

worth of lime
worth of phosphates
worth of sulphur
worth of magnesium
worth of boron
worth of manganese
worth of copper + useful amounts of molybdenum, cobalt, selenium, zinc and iron

All of the nutrients are available to the crop.

Total value c.£180.00 per tonne !

Your cost only per tonne delivered and spread depending on location and load size.

Can you afford not to use it ?

Back to Super Slag


We supply to the whole of the UK and Ireland from numerous sites around the country.

'One step towards a better tomorrow'

Super Slag products can be applied to a wide variety of crops and of course, to seedbeds and grassland and they can be used at any time of the year. They are normally spread by approved contractors using wide belt spreaders of a type capable of accurate application.

Farmer application is possible with the correct equipment. Please contact us for guidance.

Users report the following benefits when using Super Slag products:

  • Rejuvenates lack lustre soils.

  • Grain and other crop qualities and yields are improved.
  • Helps increase soil 'bug' activity so releasing locked up nutrients, particularly phosphates.

  • Old pastures come back to life.

  • Evens crops by improving poor patches of fields.

  • Stock graze more contentedly and 'do' better.

  • Provides the trace elements missing from other fertilisers.

  • Improves palatability of grass sward.

  • Super Slag Basic
    In 1998 NPK Ltd were responsible for securing supplies of steelworks slag from the South Wales steelworks after a break of many years.  After these 12 years our brand SuperSlag Basic has become well known and popular throughout the the UK.

    Super Slag Basic is modern day agricultural grade basic oxygen steelworks slag. It contains less phosphate (1.8% - 2.0% P2O5) than its well remembered and revered forerunner "Basic Slag" but has higher levels of trace elements, particularly magnesium and manganese.

    Super Slag Basic has a higher liming value than most agricultural limes and is a very economical liming material when phosphate is required at the same time.

    The high level of trace elements in addition make it an even more attractive option to other fertilisers.

    1 tonne per acre of Super Slag Basic will typically provide 38 units of phosphate, 200 units if magnesium, and 80 units of manganese and also a liming value of 58 nv.

    Typical analysis of steel works slag

    Super Slag Basic Extra
    Super Slag Basic Extra is formulated from Super Slag Basic and tri-calcium phosphate to mirror the analysis of basic slag available in the past.

    Super Slag Basic Extra has a liming value similar to ground limestone and when used regularly for its phosphate content will almost certainly eliminate the need for occasional liming on all but the most acid soils.

    Super Slag Basic Extra is available in 3 formulations: 0-6-0, 0-13-0, and 0-20-0.

    Super Slag PK
    Super Slag PK
    grades are fine grade blended compound fertilisers formulated to provide the necessary phosphate and potash requirements of crops and grassland, together with steelworks slag to provide trace elements often absent in other compound fertilisers.

    Super Slag PK builds up soil phosphate status and the CaO content reduces and can eliminate the need for regular liming.

    Super Slag PK can be tipped outside prior to spreading and can be applied at any time of the year. It is usually applied at 3 - 5 cwt per acre every 1 to 3 years depending on soil and crop needs.

    Super Slag PK is available in 3 formulations: 0-24-12, 0-20-20, and 0-16-24. Other formulations can be blended to order (25 tonne minimum quantity).

    Super Slag PK Extra
    Super Slag PK Extra is an enhanced blend for those farmers requiring a higher liming value (40 NV) and higher levels of magnesium and manganese.

    Super Slag PK Extra offers the following formulations: 0-18-8, 0-13-13, and 0-10-18 all with +4 MgO and +2 MnO.

    'phone us now and let's talk about your fertiliser needs!

    Tel: 0870 4783030
    Skype: 0208 1440197 (normal UK rate)
    Fax: 0870 4783031
    Mobile: 07778 415230
    Email: tony@npk.ltd.uk

    Head Office: Unit 1A , Uplyme Road Industrial Estate, Lyme Regis, Dorset DT7 3LS, England