The 2012 ASHS Annual Conference

The objective of this research was to investigate the physical and chemical properties of carbonized rice hull (CRH, called Huntan in Korea and Japan) and expanded rice hull (ERH) which are extensively used as root substrate components in Korea. The total porosity (TP), container capacity (CC), air-filled porosity (AP) and bulk density (BD) of ERH were 81.3%, 39.9%, 41.4%, and 0.11g·cm^-3, respectively. The TP, CC, AP and BD of CRH were 77.6%, 64.1%, 13.5%, and 0.12g·cm^-3, respectively. The percentage of easily available water (EAW) and buffering water (BW) in ERH were 38.0% and 44.1%, while those in CRH were 33.6% and 34.7%, respectively. The pH of ERH was 7.13, while CRH showed an extremely high pH (11.2). The electrical conductivity (EC) and cation exchange capacity (CEC) of ERH were 1.31 dS·m^-1 and 12.1 meq·100 g^-1 for ERH and 4.86 dS·m^-1 and 7.8 meq·100g^-1 for CRH, respectively. The concentrations of exchangeable cations in ERH were Ca 0.05, K 0.12, Mg 0.34 and 0.09 cmol+kg^-1, but those in CRH were Ca 0.02, K 0.17, Mg 0.10 and 0.10 cmol+kg^-1. The concentrations of PO₄-P, NH₄-N and NO₃-N were 1.3, 5.4 and 1.1 mg·L^-1 in ERH and 688.2, 1.0, and 0.7 mg·L^-1 in CRH, respectively, when analyzed by saturation extraction method. Each of the ash contents and cold water-, hot water-, and alkali-extracts were 11.3%, 5.5%, 6.5%, and 18.8% in ERH, and 38.5%, 4.8%, 6.7%, and 9.0% in CRH, respectively.