Growth of Ornamental Plants in Container Media Amended with Biosolids Compost

The use of biosolids compost, in the formulation of media used in the commercial production of container grown nursery crops, has been slow in the Northeast region of the United States. When biosolids compost is used in growing media, it is limited to small percentages. Regulations in Connecticut restrict the use of most biosolids compost to growing media for containerized ornamental plants and landfill cover. Information on the benefits of using biosolids compost, to grow a wide range of plant species in containers, could increase usage by nurseries. Seven species of flowering annuals, nine species of herbaceous perennials and eight species of woody ornamentals were grown in media containing 0, 25, 50, and 100 percent (by volume) biosolids compost, in combination with a mixture of bark, peat and sand. Biosolids compost came from the Metropolitan District Corporation (MDC) facility in Hartford, Connecticut. It was a mixture of wood chips and digested biosolids (3:1 by volume). Optimal plant growth generally occurred in media containing 50 and 100 percent compost. Plants growing in media high in compost were often somewhat stunted and chlorotic for several weeks after planting probably due to higher levels of salinity and ammonium nitrogen in their media. However, by the middle of the growing season these plants had recovered and at season's end, they were often superior to plants grown in media with less compost. Increasing proportions of compost generally increased the amounts of plant nutrients and heavy metals in media while decreasing air filled pore space. All heavy metal concentrations were below levels of concern.