Release of Mineral Elements and Heavy Metals Restrained in Organic Residues and Their Effects on Physocarpus opulifolius `Nanus' Grown in Containers

Abstract

The use of waste in ornamental culture seems to be the best optional method of disposal. However, the amount of available mineral elements in organic residues is not equilibrated with the mineral needs of plants. In this context, this study was performed to evaluate the influence of fresh bio-filters (FBF), composted sewage sludges (CSS), and composted de-inked sludges (CDS) on the mineral composition of substrate water solution. Substrates containing 10% of each organic residues and control substrate (4 peatmoss, 5 composted conifer bark, and 1 fine crushed gravel, by volume) were potted in 5-L containers. An experiment was conducted with Physocarpus opulifolius `Nanus' plants and a soluble fertilizer 20N–20P–20K (400 mg/L of N). Another experiment was carried out without plants and without fertilization. In the two experiments, the four substrates were randomized in a complete block design with six replications. All containers were watered every 2 weeks until leaching (inspired by the pour-through method described by Wright, 1986) and a sample of each leachate was collected for analysis. Growth parameters were statistically analyzed. The content of nutrient elements in the water solution of substrates with plants and with fertilization was higher than their content in the water solution of substrates without plants and without fertilization. However, the content of heavy metals was quite similar with the two fertilization regimes and was below the undesirable limits. Substrates amended with CSS released a higher quantity of P, K, S, and Na than substrates amended with FBF or CDS. Moreover, Physocarpus plants grown in CSS were significantly larger than those plants grown in the control substrate. The results obtained in media containing FBF or CDS were similar to those obtained in the control substrate.