Hemp-Based Phytoaccumulation of Heavy Metals from Municipal Sewage Sludge and Phosphogypsum Under Field Conditions

The aim of this study was to evaluate the ability of three hemp cultivars to accumulate heavy metals under sewage sludge (SS) and phosphogypsum (PG) application. The field study was carried out from 2014 to 2016 on Luvisol (loamy sand) in Poland. The experiment scheme included five treatments-T0: the control without fertilization, T1: 170 kg N (nitrogen) ha(-1)from sewage sludge, T2: 170 kg N ha(-1)from sewage sludge and 100 kg ha(-1)of phosphogypsum, T3: 170 kg N ha(-1)from sewage sludge and 500 kg ha(-1)of phosphogypsum, and T4: 170 kg N ha(-1)from sewage sludge and 1000 kg ha(-1)of phosphogypsum. It was found that the application of municipal sewage sludge enriched the soil with the bioavailable forms of heavy metals to the greatest extent and contributed to the highest increase in their contents in vegetative and generative organs of hemp plants. These parameters showed a phosphogypsum dose-dependent decline, which could hinder the phytoextraction process. The greatest extractions of heavy metal(loid)s (HMs) from the soil treated with SS and PG were achieved by the Tygra variety, which had the highest bioconcentration factor (BCF) and biomass yield.