Biochar

Plant charcoal that holds water and nutrients in the soil for years.

What it's for: A long-lasting soil improver. Increases aeration, structure and water and nutrient retention, buffers pH in acid soils, damps sudden temperature swings and activates plants' natural defences. Stores over three times its weight in CO₂.

Best for: Pots, lawn, vegetables, trees and compost. Sandy soils that will not hold water.

When to apply: At planting or transplanting, and in compost layers.

How often: 1 time per year.

Dose: Pots 15% of the substrate at potting on, or 2 tablespoons for maintenance. Vegetables 0.5 l/m². Trees and fruit 3-5 l in the bottom of the planting hole. Lawn 0.5 l/m². Compost: thin layers.

How to apply: Mix in well. For trees, cover and water in generously.

Worth knowing: Charge it first: always use with molasses (5) or worm humus (13). Uncharged biochar absorbs nutrients from the soil in its first year instead of supplying them.