The effectiveness and consistency of source-separated municipal solid waste and bark composts as components of container growing media

Abstract

Rooted cuttings of Cotoneaster dammeri cv. ‘Coral Beauty’ were grown in containers in combinations of source-separated municipal solid waste (MSW) compost and peat (100:0, 75:25, 50:50, 25:75 by volume), or spruce bark compost and peat (similar proportions) in each of the two consecutive years. MSW compost was obtained from the same commercial composting facility, but it was not consistent in chemical composition, bulk density, soluble salt content or pH from year to year. Plant growth, substrate physical properties and end-of-season foliar nutrient levels were measured for all media treatments. Soluble salt content was initially high in media containing MSW, but declined to <1 mS cm −1 within 1 month of potting. Plant growth in MSW-based media was equal to, or greater than that in bark-based media, and was similar for both years. Poorest growth was obtained in 100% bark, and 100% MSW media, but growth was strong at ratios up to and including 75:25 MSW:peat. End-of-season foliar nutrient levels were higher in 1997 than in 1996 in MSW-grown plants, reflecting the generally higher nutrient concentrations in the 1997 compost. Heavy metal uptake was no greater in MSW than in bark media and there were no signs of nutrient deficiency or toxicity at any time during the study. The results indicate that despite inherent variability in the texture and composition of composted MSW, it could form a useful component of a standardized growing medium for woody nursery plants.