Growth and mineral nutrient status of containerized woody species in media amended with spent mushroom compost

Eight deciduous ornamental shrubs--deutzia (Deutzia gracilis Siebold and Zucc.), dogwood (Cornus alba L. 'Argenteo-marginata'), forsythia (Forsythia X intermedia Zab. 'Lynwood Gold'), ninebark [Physocarpus opulifolius (L.) Maxim.], potentilla (Potentilla fruticosa L. 'Red Ace'), privet (Ligustrum vulgare L.), rose (Rosa L. 'John Franklin'), and weigela [Weigela florida (Bunge) A.DC. 'Variegata Nana']--were grown in trickle-irrigated containers with 100% bark (control) or with bark and 33%, 67%, and 100% (by volume) of each of three sources of spent mushroom compost (unweathered, weathered, and unweathered compost leached with water). Despite large variation in species growth response to sources and levels of compost, most grew equally well or better in the compost-amended regimes than in 100% bark and were influenced little, or not at all, by initial or prevailing salt levels in the media. Shoot and root dry weight of dogwood, forsythia, ninebark, rose, and weigela (all sources), and shoot dry weight of deutzia and potentilla (weathered source only), increased linearly or curvilinearly with increasing compost levels. The reverse relationship occurred (all sources) in shoot and root dry weight of privet and root dry weight of weigela and potentilla. Leaf nutrients (N, P, K, Ca, Mg, Fe, Mn, and Zn) tended to increase with increasing compost levels, but not all species showed this response with all nutrients. Regardless of compost source or level, all shrubs were of marketable quality when harvested, except privet, which showed leaf chlorosis in all compost-amended regimes.