Biomass allocation and nutrient use in fast-growing woody and herbaceous perennials used for phytoremediation

This study assessed the suitability of two deciduous woody perennials (Salix spp. and Populus spp.) and two summer green herbaceous perennials (Phragmites australis and Urtica dioica) for purification of nutrient enriched wastewater. The main hypothesis tested was that species with a particular trait combination of high relative growth rate (RGR), low nutrient productivity (A) and high mean residence time (MRT) of nutrients would be most effective in accumulating nutrients. The nitrogen and phosphorus use efficiency at the whole plant level was analysed. Four treatments comprising two possible phytoremediation substrates (municipal wastewater and landfill leachate) and two control plant nutrition situations (balanced nutrient solution and pure water) were applied in four replications to the four plant species. Generally, all four species studied showed a high RGR and a low P productivity in the balanced nutrient solution treatment, while the opposite (low RGR and high P productivity) was seen in the phytoremediation substrate and pure water treatments. The general conclusion is that if P is present in marginal proportions in the wastewater, a vegetation filter with Phragmites would have an advantage since biomass and nutrient accumulation in Phragmites does not decrease as much during phytoremediation as that in deciduous woody perennials.