Sewage sludge and the energy balance of Jerusalem artichoke production - A case study in north-eastern Poland

Sewage sludge is a specific by-product of wastewater treatment and its use as fertilizer is the most rational and the cheapest strategy for managing this waste product. In this study, the production of aerial biomass, energy inputs and the energy efficiency ratio of Jerusalem artichoke (JA) fertilized with sewage sludge at rates equivalent to 100 and 160 kg N ha(-1) were evaluated in a field experiment conducted in north-eastern Poland in 2018-2020. In conventional treatments supplied with mineral fertilizer, energy inputs were determined at 23.5-28.1 GJ ha(-1) in the year of plantation establishment and at 12.6-18.3 GJ ha(-1) in the second and third year. In treatments fertilized with sewage sludge, the demand for energy was lower by 27-32 % in the first year and by 48-54 % in the second and third year. Regardless of fertilizer type the optimal nitrogen rate was 100 kg ha(-1) (11.7-11.9 Mg ha(-1) DM y(-1)). The biomass of JA plants supplied with 100 kg N ha(-1) was also characterized by the highest energy output and energy gain. Energy gain was 5-11 % higher per hectare, and the energy efficiency ratio was nearly twice higher in treatments supplied with sewage sludge than with mineral fertilizer. (C) 2021 The Author(s). Published by Elsevier Ltd.