RESPONSE OF 4 CONTAINER-GROWN WOODY ORNAMENTALS TO IMMATURE COMPOSTEDMEDIA DERIVED FROM WAXED CORRUGATED CARDBOARD

Four containerized deciduous ornamental shrubs [deutzia (Deutzia graci lis L.), silverleaf dogwood (Cornus alba 'Elegantissima'), red-osier d ogwood (Cornus sericea L.), and ninebark (Physocarpus opulifolius L.)] were grown during each of two separate growing seasons using 12 diffe rent immature (nonaged) composts as media (year one, 12 weeks from sta rt of windrowing; year two, 16-weeks) and also two control nursery mix es (100 percent ground pine bark; and 80:15:5 by volume of pine bark:s phagnum peat:top soil). The compost formulations (volume basis) consis ted of spent mushroom substrate (50 percent), waxed corrugated cardboa rd, 0 percent, 25 percent, or 50 percent), and/or pulverized wood wast es (50 percent, 25 percent, and 0 percent). Supplemental N was added t o some composts as poultry manure (18 kg . m(-3)), soybean wastes (24 . kg . m(-3)), or both at the same application rates. Despite the imma turity of the compost media and the presence of high initial contents of soluble salts primarily from the spent mushroom substrate (EC less than or equal to 6.4 dS . m-1, 1:1 v/v medium:water extracts), the top dry weight (averaged over two seasons) of each of the four species gr own in compost media, regardless of waxed corrugated cardboard (WCC) l evel, exceeded that obtained in 100 percent pine bark. Compared with t he 0 percent WCC compost, plants of all four species grew better in 25 percent and/or 50 percent WCC compost media and growth in these treat ments was more (silverleaf dogwood), similar (deutzia and red-osier do gwood), or less than (ninebark) that in the 80:15:5 nursery mix. Rapid leaching of the potentially toxic soluble salts from the containerize d compost media within days after planting minimized any adverse effec ts on the plants. There was no difference in foliar concentrations of N, P, K, Ca, Mg, Fe, Mn, and Zn due to WCC level, or to the N suppleme nts which had little or no effect on growth. The foliar contents of he avy metals (Cu, Ni, Cr, Cd, Co, and Pb) were low and/or below detectio n limits.