Amelioration of Horticultural Growing Media Properties Through Rice Hull Biochar Incorporation

The current study was conducted in order to examine the applicability of rice hull derived biochar (BC) to improve the properties of growing media (GM). Biochar was incorporated into a growing media composed of coir dust, perlite and vermiculite at 0, 1, 2 and 5 % (w/w). Subsequently, the physicochemical properties of the GM-BC mixtures were determined in the cultivation of kale (Brassica oleracea L. var. acephala) for 25 days through the observation of the plant growth response. During kale cultivation in the GM-BC mixtures, the leachates were collected and analyzed to determine the changes in nutrient levels due to BC amendment. Application of rice hull-derived BC increased the retention of nutrients in the growing media due to a biochar-induced increase in cation exchange capacity, in addition to the biochar nutrient supply such as potassium and phosphorus. Furthermore, a higher water content of the growing media was observed when BC was used as an amendment, mainly due to the increased proportion of pore space available for water storage. The growth rate of kale was also increased as the biochar incorporation rate was increased. For example, the dry weight of the kale shoots was 150 % higher when grown in media containing 5 % GM-BC mixture than with the control growing media (with no biochar). From these results, it can be concluded that the rice hull-derived biochar would be a practically applicable amendment to improve the properties of the growing media.