Evaluation of municipal solid waste compost as a growing media component for potted plant production

Increasing limitations to peat exploitation make it necessary to look for alternative organic materials as constituents of plant substrates. In this work, two municipal solid waste (MSW) composts were evaluated as growing media components for potted plant production, in comparison with Sphagnum peat (P) and composted pine bark (CPB). MSW composts showed higher electrical conductivity and pH values, as well as higher cation exchange capacity and nutrient supply potential than P and CPB. Physical properties of the substrates were generally within the recommended ranges for production of ornamental plants, although water capacity at -10 cm suction was slightly low. Substrates were prepared by combining the compost with P or CPB in different proportions (25, 50 and 75% by volume). Plant tolerance to the mixtures was evaluated by means of the cress (Lepidium sativum L.) germination test and the spring barley (Hordeum vulgare L.) growth test. Poor germination and growth were only observed in substrates with 75% compost, whereas substrates with 25% compost produced higher cress germination and better spring barley growth than P or CPB alone. The MSW composts evaluated can be used in the preparation of substrates, as partial substitutes for peat or composted pine bark, provided that they are not employed in proportions higher than 50%. Using MSW compost for substrate preparation would be economically attractive and would help to conserve finite peat resources.