Biochar is a stable, carbon-rich material made by heating organic matter such as wood, crop waste, or manure in a low-oxygen process called pyrolysis. In gardening and horticulture, it is used as a soil amendment because its porous structure can improve water retention, aeration, nutrient holding capacity, and microbial habitat in soil.
Fresh biochar is usually “charged” before use by soaking or mixing it with compost, fertilizer, or nutrient-rich organic matter. Uncharged biochar can temporarily tie up nutrients as it adsorbs them from the soil. Its effects vary with soil type, particle size, feedstock, and application rate, but it is generally most beneficial in sandy soils, degraded soils, or low-organic-matter growing media.
Biochar differs from charcoal intended for fuel or grilling. Horticultural biochar is produced and processed to avoid additives, lighter fluids, or contaminants that may harm plants or soil organisms.
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