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Notes On John Innes Compost.

July 1st, 2016 · No Comments

John Innes Compost, ingredients.

Sterilised Loam 7 parts,
Peat 3 parts and, (John Innes Nos. 1, 2 and 3)
Sharp sand 2 parts

Sterilised Loam 2 parts
Peat 1 part and, (John Innes Seed and Ericaceous Compost)
Sharp sand 1 part

As a rough guide: J. I No. 1 for 3 -3.5 inch pots
J. I No. 2 for 5 – 6 inch pots and,
J. I No. 3 for pots above these sizes

Fertiliser base
John Innes No 1
0.6kg ground limestone
1.2kg hoof and horn base per cubic metre
1.2 kg superphosphate
0.6kg potassium sulphate

John Innes No 2
0.6kg ground limestone
2.4kg hoof and horn base per cubic metre
2.4kg superphosphate
1.2kg potassium sulphate

John Innes No 3
0.6kg ground limestone
3.6kg hoof and horn base per cubic metre
3.6kg superphosphate
1.8kg potassium sulphate

John Innes Seed Compost
0.6kg ground limestone base per cubic metre
1.2 kg superphosphate

John Innes Ericaceous Compost
0.6 kg Flowers of sulphate base per cubic metre
0.6 kg superphosphate


Loam is the most important ingredient in the compost as it is the main constituent of the compost giving the compost its main bulk.It also forms the base of plant nutrition by supplying clay, which has a cation and anion exchange capacity,that is,it absorbs and releases plant nutrients as required.Loam also contains essential micro elements and varying quantities of organic matter,which provides a slow release of nitrogen to the plant.

Loam is soil composed of sand,silt and clay and organic material in roughly even proportions,at a ratio of around about 40, 40 and 20%,respectively.It is porous,which allows for good air circulation but is also retentive of moisture.

The loam should be sterilised to rid the substrate of harmful pathogens and weed seed.
Both the loam and the peat used for John Innes Compost mixes should be able to pass through a 9 mm sieve.
Sphagnum Moss Peat in the John Innes Compost increases the total porosity and improves both the aeration and the water-retaining capacity.Peat over time breaks down into humus.The best peat for compost making has been traditionally sphagnum moss peat,which is found mainly in the northern hemisphere,however,large-scale peat harvesting is not sustainable.It takes thousands of years to form but very little time to dig out and more eco-friendly alternatives are becoming more and more available.

Products produced from collected garden waste by local authorities make a good alternative and have to meet the national standard BSI PAS 100.This means that they have been produced to a high quality.

These soil conditioners,which have high organic matter content,are ideal for use for digging into the garden soil to condition and generally improve the structure of the soil and increase water and nutrient holding.

For compost incorporation,however,peat free alternatives have produced unreliable results.A compromise in the form of reduced peat compost has shown encouraging signs,the peat element being reduced by fifty percent of other organic material.

It is up to the individual gardener or grower user as to the way forward.
The sand element added to John Innes Composts is used as a physical conditioner to allow excess water to drain from the compost and thus prevent waterlogging.It also helps to provide stability for larger plants.Clean,lime free sand of a particle range from 0.063 mm through to 5mm,coarse sand is the standard used in the compost manufacturing industry.

Information provided by: http://www.gardeningknowledge.co.uk/JohnInnesIngredients.asp

Tags: Tim Whitcombe

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