Wulpak Used as a Mulch or an Amendment for Nursery Potting Substrates

Wulpak is a pelleted waste by-product derived from wool products manufacturing litter. It contains no manure or compost although it contains significant plant available nutrients. Preliminary reports suggest that mulching the top of container grown nursery crops provides a weed, moss and algae barrier and acts as a starter fertilizer by enhancing green color and stimulating new growth. To evaluate the usefulness of Wulpak, two studies were conducted. The objective of the first study was to compare the effect of supplemental fertilizing and use of Wulpak as a top mulch compared to incorporation into the potting substrate on plant growth, foliar and substrate nutrient concentrations. The objective of the second study was to evaluate Wulpak compared to PennMulch, a pelleted newspaper product, applied at two mulch depths for control of common nursery weeds. After 70 days, petunias were larger when top-dressed with supplemental Controlled Release Fertilizer (CRF) compared to the standard pine bark substrate or the Wulpak mulch or incorporation-only treatments. Tissue N was not significantly different among any treatments. Tissue P was higher in all Wulpak mulch and incorpation treatments compared to the pine bark standard. Leachate pH was consistently lower in the Wulpak top mulch treatments. Common groundsel and horseweed were controlled by all mulch treatments; although, after three months some common groundsel emerged in the 0.6 cm PennMulch pots. Spotted spurge and longstalked phyllanthus were controlled by both depths of Wulpak and by 1.3 cm PennMulch, but not by 0.6 cm PennMulch. Crabgrass was controlled only by the 1.3 cm Wulpak treatment.