SoilFixer’s Fine Biochar (0–8 mm) is a high-quality soil enhancer ideal for precision applications in gardens, pots, raised beds, and lawns. The finer granule size means faster integration into soil, improved surface area for microbial colonisation, and quicker interaction with nutrients and water. It boosts water retention, reduces nutrient leaching, and supports strong root development—especially beneficial for seedlings, potted plants, and sandy soils. Sustainably produced in the UK, this biochar also promotes long-term soil health by supporting beneficial microbes and mycorrhizal fungi.

How to Apply Biochar

Raw biochar needs time to absorb nutrients and develop root zone relationships – this can take 3 to 6 months. This ‘lag’ period can be shortened by charging (activating or enriching) your biochar before adding it to the soil.

Methods to charge your biochar:

• Add it to your composting process and mix it into your compost
• Soak it in a liquid fertiliser before applying

If you prefer a ready-to-use product, check out our Biochar Multi-purpose Compost (SF40).

The most powerful benefits of biochar come from its interactions within the root zone. Ideally, dig biochar in when planting (e.g. seed drills, tree holes, or when cultivating). If this isn’t possible – such as in no-dig gardening – biochar can also be used as a top dressing or hoed into the top few centimetres of soil.

Should I Use Powder or 0–8 mm Granules?

Our 0–8 mm grade biochar achieves the ideal balance of particle sizes:

• Approx. 40% <2 mm
• Approx. 60% 2–8 mm

Trommel sieves may allow a few long, thin bits to pass, so some particles may slightly exceed 8 mm.

We do not recommend using fine biochar powder (amorphous biochar) because it lacks the macro-pores needed by soil microbes. We also advise against using very large granules (>8 mm), as they offer low pore surface area and can negatively affect soil aggregation (tilth).
Read more in our biochar blog.

How Much Biochar Should I Apply?

• Apply 1 kg per square metre (1 kg/m²)

This is roughly equal to 5% by volume, although it depends on soil depth.
For more information on how to calculate by area, volume or weight – and how to stretch your biochar budget – see our application ratio blog.

Volumes and Weights

Biochar naturally absorbs water, and moisture content varies with the seasons. That’s why we sell by volume (litres) and provide an approximate weight.

• 20 litres ≈ 10 kg
• 40 litres ≈ 20 kg

Our product contains approximately 40% water by weight.
If comparing prices across suppliers, make sure you’re comparing volume (litres) or adjusting prices to reflect £/kg of dry biochar.