Evaluating Pulp and Paper Sludge as a Substitute For Peat Moss in Container Media

Pulp and paper sludge from a newsprint mill was composted for 6 weeks and evaluated as a substitute for peat moss in container media. One-year-old seedlings of lilac (Syringa vulgaris L.) and amur maple (Acer tataricum L. ssp. ginnala (Maxim.) Wesm.) as well as rooted cuttings of cistena plum (Prunus × cistena Hansen) were planted in #1 plastic pots that contained a pine bark and sand mixture (2:1 by vol) or pine bark and sand amended with either 25% or 50% peat moss or composted paper sludge. A 75% compost medium that consisted of composted paper sludge and sand (3:1 by vol) was also used in the study. Plant height was measured every 4 weeks. After 14 weeks of growth, shoot dry weight and final plant height were measured. All plants in compost-amended media grew as well as or better than those in peat-amended media, regardless of the species grown. Lilac plants in 25% compost produced almost double the amount of shoot dry weight and were 80% taller than plants in the bark: sand or 25% peat media. Maple plants in 50% compost produced at least 33% more shoot dry weight than those in either peat-amended medium. Plum cuttings in 25% compost grew at least 53% taller than those in either peat-amended medium. These results demonstrated that composted paper sludge from newsprint production was a worthy substitute for peat moss in a container medium for the three species tested.