Efficacy and physical properties of ground, composted rice hulls as a component of soilless substrate for selected bedding plants

Abstract: Ground, composted rice hulls were combined as a root substrate component with peat moss and coir at five rice hulls percentages (0, 25, 50, 75, and 100) in a factorial design. Seventy-five percent of the rice hull particles were 0.51 to 1.40 mm and 90% of the particles were 0.51 to 2.00 mm. In physical property evaluations, increasing the percentage of rice hulls in both the peat moss and coir series of substrates increased the dry bulk density and airspace at container capacity; however, as air space increased, container capacity and available water decreased. In the first two of three plant growth experiments, Impatiens walleriana Hook. f. 'Super Elfin White' was grown in 288 cell plug trays. In the third experiment, Verbena Xhybrida Voss. 'Romance Deep Rose' was grown in 48 cell bedding plant flats. Due to problems with high pH in the coir, only the peat moss growth results were reported. Overall, growth was best in 25% rice hulls plus 75% peat moss. Rice hulls increased substrate Ca²+ and Mg²+ in both the peat moss and coir. Adding rice hulls to the substrate increased K+ in peat and decreased K+ in coir. There was no effect of rice hulls on substrate NO₃^- -N, NH₄+-N, and PO₄-P in the substrate solution. Ground, composted rice hulls are a potential alternative component of soilless substrate for plugs and bedding plants.