Assessment of Long-Term Nutrient Effective Waste-Derived Growth Media for Ornamental Nurseries

Abstract

This study was conducted in order to examine the potential use of nutrient-rich biosolid in combination with crop residues on the growth of ornamental plants that aims to increase sustainable waste resource recovery and reuse. Locally available crop residues namely, hazelnut husk (HHC), rice hull (RHC), corn straw (CSC) and sawdust (SWC), were composted by mixing with municipal wastewater biosolid (1:1 v/v). After 6-month composting, four different growth media were prepared. The suitability of each growth medium was evaluated by comparing their properties to standard peat and by measuring the plant growth parameters of two well-known ornamental species, Cupressus macrocarpa and Thuja occidentalis, over two consecutive years. The growing experiments were performed in a commercial producer greenhouse and the plants were grown under conditions similar to those used by growers. The key physical and physicochemical properties of the growth media, such as bulk density, porosity, air porosity, water holding capacity, biological stability, pH, EC and organic matter were within the acceptable ranges. Pearson's correlations and stepwise regression analysis indicated that nutrient properties, such as carbon-to-nitrogen ratio, cation exchange capacity, humification index, and total phosphorus and potassium, were most influential on plant growth parameters. The calculated comprehensive growth index values for C. macrocarpa (0.86, 0.89 and 0.78) and T. occidentalis (0.77, 0.71 and 0.74) for HHC, SWC and peat medium, respectively, were higher than RHC and CSC. This study proves that biologically stable crop residues with biosolid could be used as a growth medium and shows that peat could be successfully replaced by HHC and SWC.