Effect of wastewater sludge treatment on early growth and physiological responses of willow (Salix spp.) and poplar (Populus spp.) pot-grown plants

Ivaylo Tsvetkov,Svetla Marinova,Nikolina Tzvetkova

doi:10.3897/silvabalcanica.22.e58528

Ivaylo Tsvetkov, Svetla Marinova + Show 1 more

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https://doi.org/10.3897/silvabalcanica.22.e58528

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Abstract

Combining biomass production from fast-growing woody species with wastewater treatment is an attractive concept from the economic, energy and environmental points of view. A pilot experiment on study-ing the effect of wastewater treatment on the early growth and initial physiological responses of willow and poplar plants was carried out in greenhouse conditions. The survival, height growth, net photosyn-thesis, stomatal conductance and transpiration of two hybrid clones of black poplar (Populus x euroameri-cana (Dode) Guinier) (I-214 and I-45/51) and white willow (S. alba L.) pot-grown plants treated with different doses of agrochemically characterised wastewater sludge were studied during the establishment year. The height growth and number of resprouted willow shoots were also measured during the second year after cutting, at the end of the vegetation season. While the early growth height of poplar clones was markedly affected by the clone origin and wastewater sludge treatment, the latter did not considerably influence the height of the willow plants either during the establishment and the following year, but essentially increased the number of resprouted shoots during the second vegetation season. The rate of CO2 assimilation of willow plants was significantly influenced by the wastewater sludge treatment, with plants grown at the higher doses displaying higher photosynthetic performance. The application of wastewater sludge had no essential impact on the values of the physiological parameters of the poplar plants, but particular responses were found among the clones.

Highlights

The initial efforts for diversification and seeking for alternative sources of energy to the conventional ones were induced by the oil crisis in the 70ies, when the cultivation of short-rotation willow coppice introduced in Sweden promoted the intention of replacing fossil fuels with new energy sources (Dimitriou, Aronsson, 2005)
The organic nitrogen in the sludge partially passes into a mineral form absorbable for the plants, namely ammonium (-NH4) and nitrate (-NO3) salts. The latter mobile macronutrients forms, together with mobile P and K, are those utilised by the plants (Zhang et al, 2017)
Our results demonstrate that the early growth height of the experimental poplar clones was significantly affected by the clone origin and wastewater sludge application

Summary

Introduction

The initial efforts for diversification and seeking for alternative sources of energy to the conventional ones were induced by the oil crisis in the 70ies, when the cultivation of short-rotation willow coppice introduced in Sweden promoted the intention of replacing fossil fuels with new energy sources (Dimitriou, Aronsson, 2005). The application of wastewater sludge in agricultural lands is governed by the Council Directive 85/278 (Council of European Communities, 1986). This Directive is a legal framework document, which regulates the application of wastewater sludge in the agriculture of EC countries, but every country is allowed to introduce more strict legislative measures. There is a lack of crucial knowledge about the impact on woody plants growth, biomass production and the safest and most beneficial way of the wastewater sludge utilisation. In this context, pot studies could generate useful information in a short period of time and at low costs (Weih, 2001)

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