Effects of some peat-alternative substrate on the growth and chemical composition of pelargonium

Increasing demand and rising costs for peat in horticulture as well as ecological factors have led to the investigation for alternative growing media. This paper reports the results of experiment performed to test four composts-based substrates tested for production of pot Pelargonium (Pelargonium zonale 'Survivor Blue'). The mature compost after 18 months decomposition, were used as substrate components for pelargonium, using the partial substitution (50%, v/v) of the commercial sphagnum peat (sp). The composts composition was as follows: SS - sewage sludge (70%), rye straw (30%); compost SSd - sewage sludge (70%), coniferous tree sawdust (30%); compost SPS - sewage sludge (35%), potato pulp (35%), rye straw (30%); compost SPSd - sewage sludge (35%), potato pulp (35%), coniferous tree sawdust (30%). Some physical and chemical properties of these substrates were determined. The substrate of 100% sphagnum peat with addition of compound fertilizer was used as the control. Plants were grown in plastic tunnels with natural period conditions. There was no top-dressing during cultivation. The most beneficial effect on the foliage, chlorophyll content, flowering and decorative value of pelargonium was observed for the substrate containing compost SS. The substrate containing compost SPSd was found the least effective for the Pelargonium performance. Content of N, K, Cd, Ni and Pb in Pelargonium leaves was dependent on the kind of composts used for substrate preparing. The concentrations of trace elements in leaves were far lower than the ranges considered phytotoxic for vascular plants.