Testing composted bamboo residues with and without added effective microorganisms as a renewable alternative to peat in horticultural production

This study assesses the potential for composted bamboo residues to serve as a renewable replacement for peat in horticultural growing media. Bamboo residues and wheat bran compost (ratio 90:10) were prepared in two batches, with (B1) and without (B2) effective microorganisms, and mixed with peat at 25%, 50%, 75%, and 100% by volume. Both batches were then used in greenhouse tests with two horticultural plants, Osmanthus fragrans (Thunb.) Lour. and Hydrangea macrophylla (Thunb.) Ser., using pure peat as a control. Batch B1 showed higher peak temperature and longer thermophilic phase than B2 during composting, and had higher N but lower total C and C/N ratio than B2. The addition of either batch to the growth media increased bulk density, particle density, and air space compared with pure peat, but decreased total pore space and total water-holding capacity. At lower compost content, the physical and chemical properties of the test batches were very similar to those of an ideal substrate, especially those mixed with B1. Plants grown in media mixed with B1 (25% or 50%) or B2 (25%) showed no significant differences in growth rates for height and ground diameter compared to those of the pure peat control. The results suggest that using effective microorganisms can increase mineralization during composting of bamboo residues, and that composted bamboo residues should be considered as a component of horticultural growth media in partial substitution for costly and less sustainable peat.