Biochar as a growing media additive and peat substitute

Environmental concerns raised the demand for alternative growing media substituting <i>Sphagnum</i> peat. However growing media formulations still depend on peat and alternatives are limited. Biochar is carbonized plant material and could be an appropriate additive or even substitute for <i>Sphagnum</i> peat. Freshly produced, it is free from pathogens, has a low nutrient content (if produced from nutrient-poor feedstock), a very high structural stability and likely other favourable properties such as air capacity and water-holding capacity. <br><br> Preliminary tests were conducted to compare biochar with other growing media and growing media additives. The growth of a miniature sunflower, pH and electrical conductivity (EC) was measured in different growing media such as biochar, perlite, clay granules, <i>Sphagnum</i> peat and peat mixed with biochar in the ratios 1 : 4, 1 : 1 and 4 : 1 (25, 50 and 75%, by volume). <br><br> Fresh biochar has a similar EC to peat which is even lower after rinsing with water. Due to the relatively high pH of biochar, it could be added to peat instead of lime in a concentration of up to 75%. The growth of the sunflower was similar in all growing media. Only the plant weight was slightly higher of plants that grew in perlite or peat. There is a large potential for optimization such as selection of particle size and feedstock for biochar production and growing media formulations for specific plant requirements