The possibility of using sewage sludge for energy crop cultivation exemplified by reed canary grass and giant miscanthus

Abstract

Abstract Energy crops, on account of high biomass yields, have high nutrient requirements in relation to macroelements. Municipal sewage sludge can be a potential source of micronutrients for plants with high nutrient requirements. The use of macronutrients from sewage sludge by energy crops is an alternative form of nutrient recycling from organic waste. The aim of the research was to assess the content, uptake and use of N, P, K, Ca, Mg and Na from municipal sewage sludge by reed canary grass (Phalaris arundinacea L.) and giant miscanthus (Miscanthus × giganteus Greef et Deu). The effect of sewage sludge on the ratios between macroelements in the biomass of the tested plants was also assessed. The multi-year field experiment involved four levels of fertilization with sewage sludge at doses of 0, 10, 20, 40, 60 Mg DM·ha−1. Due to the low potassium content in this waste, supplementary potassium fertilization (100 kg K·ha−1 in the form of 40% potassium salt (KCl)) was applied once on all plots. It was established that the increasing doses of sewage sludge had a considerable effect on the increase in the content and uptake of N, P, K, Ca, Mg and Na by the biomass of the tested energy crops. The research shows that, compared to giant miscanthus, reed canary grass had a higher macronutrient content. The largest amount of uptaken N, P, K, Ca and Mg was found in reed canary grass (at a dose of 40 Mg DM·ha−1), whereas Na was detected in giant miscanthus (at a dose o 20 Mg DM·ha−1). It was established that giant miscanthus, on account of its higher yielding, recovers macroelements from sewage sludge applied to soil at a dose of 10 Mg DM·ha−1 to the greatest extent. The increasing doses of sewage sludge considerably decreased the value of K:Mg, Ca:Mg, Ca:P ratios in miscanthus biomass yield. The applied doses of sewage sludge (40–60 Mg DM·ha−1) increased the value of K:Ca, Ca:P, K:Na ratios in miscanthus biomass yield.