Evaluation of Sewage Sludge Effects on Soil Properties, Plant Growth, Mineral Nutrition State, and Heavy Metal Distribution in European Larch Seedlings (Larix decidua)

Abstract

This study investigates the impact of sewage sludge application on nutrient uptake and growth parameters of larch seedlings (Larix decidua). Heavy metals and minerals distribution were also addressed. Sludge was applied at three loading rates (0, 30, and 60 Mg DW ha−1), and harvesting was done after 6 weeks. The results demonstrated that nitrogen and phosphorus contents increased significantly in top soil of pots receiving sludge, while no modification appeared in bottom soils. Similar results were obtained only at higher dose for Cu and Zn concentrations. However, no such difference was observed for total soil micronutrients. Despite a significant increase in plant nitrogen concentration, the use of sewage sludge did not affect larch seedling growth at this stage. Nitrate reductase activity decreased significantly with increasing sludge application rates. For all heavy metals, sludge application did not lead to an increase in plant concentrations, but the superoxide dismutase activity measured in needles and lateral roots increased significantly. It was concluded that sewage application brought about notable benefits to soil fertility, but Cu and Zn accumulation needs to be monitored.