Characteristics of kuntan (rice hull charcoal) asoa medium of soilless culture

Abstract

The physical and chemical properties of kuntan (rice hull characoal) and its application to the rooting medium of soilless culture were investigated.
Kuntan showed microporous structures under the electron microscope. Light weight, good air permeability and moderate water holding capacity of Kuntan seemed to be ascribed to its porous structures.
From the measurements of particle size and three phase (solid, moisture and air) distributions, Kuntan was proved to be good medium for soilless culture, unless its poraus structures were destroyed.
Cation exchange capacity (CEC) and maxium water holding capacity were higher in kuntan obtained at higher temperatures beyond 500°C. While pH and water soluble K₂O content apparently increased with increasing temperature.
In water immersion test pH became constant within 24 hours, on the other hand, EC and soluble K₂O continued to increase gradually with immersing time, indicating the existence of hardly soluble potassium in kuntan.
In application of urea to the new kuntan, ammonification occured rapidly, but nitrification was negligible with scanty nitrification. In the old kuntan once used in melon cultivation, however, some nitrification was observed.