Co-blended Composts for Production of Potted Poinsettia

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  • 1 Dept. of Natural Resource Sciences and Landscape Architecture, Univ. of Maryland, College Park, MD 20742-5611

Production of `Top White', `Peterstar Pink', `Lilo Red', and `Red Success' poinsettias were evaluated in a treatment combinations that included 10 compost blends, three compost levels, and two commercial soilless substrates of Sunshine Mix 1 and Pro Gro 300S as controls. The compost feedstocks included PSG polymer dewatered biosolids (PSG), lime dewatered biosolids (CP), yard trimmings (YT), poultry litter (PL), and municipal solid waste (MSW Bedmininster). The PSG, PL, YT, and MSW were co-blended with CP on a 2:1 ratio (v/v), all other composts were co-blended on a 1:1 ratio (v/v). The compost levels of 33%, 50%, and 67% were mixed with peat:perlite (1:1, v/v). There were five replicates per treatment. Plants were fertilized once weekly with 200 mg·L–1 N from 21N–2.2P–16.6K. Sunshine mix produced control plants that had greater canopy diameter and plant grade than Pro Gro mix. Plant height was reduced as compost level increased from 33% to 67%. Blends of PSG:PL at the 33% and 50% levels and PSG:YT at the 33% level produced premium-quality plants. Good-quality plants, similar to those grown in Sunshine Mix, were produced with the PSG or PL compost blended with immature MSW at the 33% level; PSG:PL blend at a 67% level; PSG:YT blend at the 50% and 67% levels; and PL:YT blend at the 33% level.

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