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From 2024 sales of compost containing peat will be banned in the UK.
Step back – there are two very different uses of peat: as a growing media and as a soil improver. It was cheap enough to use for both, but going forward, we are likely to see two different solutions:
Most of the UK has heavy clay soil or at best clayey soil. It gets too wet in winter and dries to a hard crust in hot summers. What we really want is a “loamy clay top soil”. The best way to achieve this is by adding PAS100 green waste compost or a mix of compost and sand. These will improve clay in two ways:
Humic compounds will glue (bind) clay into aggregates – those small lumps that are easy to till/dig
Small bits of wood (2-10mm) (or sand (0.5-1 mm) that will ‘break-up’ clay and allow faster drainage and more aeration
There is absolutely no need to use peat as a soil conditioner, PAS100 compost and sand has it covered.
It has more humus and biochar so adds more aggregation, aeration and drainage. Used in small amounts (10%, 10:1) it is a great addition to improve any clay soil. Realistically, unless you have a robust budget, biochar super compost is going to be added each year, probably supplemented by cheaper PAS100 compost. We are already starting to see professional growers ask for a range of biochar/compost/soil mixes that take the best of each to create the perfect “top soil”. Watch this space!
Here things get a bit more “technical”. Many gardeners still attempt to grow plants in green waste compost (i.e. PAS100 compost). Compost is not a good growing media – it will fail totally or at best give you poor results.
It is too rich (i.e. has too many nutrients) – certainly for germinating seeds
It dries out very quickly – although it holds lots of water, it dries (loses it) very quickly.
(The particles of organic matter dry out really quickly and once fully dry they become hydrophobic which means they are really difficult to re-wet. (Try a simple experiment – take a handful of garden centre compost, a handful of clay soil and a handful of PAS100 compost. Wet each, roll into a ball and leave on a stone to bake in the sun. After 12 hours, tap each ball and watch what happens. The next day, wet each block and try to create a new ball by wetting.)
To create a growing media we need to mix clay soil, sand and compost – i.e. we need to recreate the John Innes mixes (types). Read our How to make the best plant growing media blog for recipes. It is unlikely you will see lots of John Innes “mixes” (i.e. with compost replacing peat in the recipe!) making a come-back into garden centres. The large suppliers of growing media (incorrectly called “all-purpose composts”) have to meet several needs that are expensive to offer via the revised John Innes range:
100% sterile (free from all pests and pathogens)
100% free from weed seeds
Light in weight, high in volume – to reduce the cost to transport it to garden centres
It still has to perform well in terms of water holding, drainage and rewetting.
Using PAS100 compost, clay and sand to make a revised John Innes mix will not meet all the above. They will also be 3-4 times heavier making them expensive to transport.
Professional plant growers and those wanting to buy ‘growing media’ will move to use new types of growing media based on wood fibre and/or coir fibre mixed with a range of slow-release nutrient fertilisers and wetting agents. We hope in earnest that these growing media cease to use the term “all-purpose compost”, and “potting compost”. Compost is the product of composting plant material. These are very unlikely to contain any green waste compost. They will be excellent growing media for germinating seeds, onward potting and in some cases filling annual containers used and baskets. But it will not be the right thing to add and improve your clay soil!
We hope this helps!
