2.3. Growth experiment
The experiment was carried out on two soil types: loamy sand (LS) and
clay (C) collected from the 0-0.2 m layer in southern Poland. The
properties of the soils used in the experiment are presented in Table 2.
The growth experiment was conducted in containers with a capacity of 500
g of soil dry mass. The experimental scheme was the same for LS and C
soils and included the following treatments: the control with no
cavitated charcoal (LS-0; C-0), a treatment with a 1.76% addition of
cavitated charcoal (LS-1; C-1), a treatment with a 3.5% addition of
cavitated charcoal (LS-2; C-2), a treatment with a 7.0% addition of
cavitated charcoal (LS-3; C-3), and a treatment with a 14.0% addition
of cavitated charcoal (LS-4; C-4). After introducing cavitated charcoal,
distilled water (up to 45% water capacity) was added to the soils and
thoroughly mixed with the material. Subsequently, soils with and without
the addition of charcoal were placed in PVC containers. After 24 hours,
seeds of Sorghum saccharatum SOS 101116 were sown. During plant
growth, the soil moisture content was maintained at 60% of the water
capacity. The experiment was carried out under laboratory conditions at
25±3 °C for 156 days. Then, plant aboveground biomass was collected, and
plant roots were separated from the soil block and thoroughly washed
with distilled water. The collected biomass was dried to a constant
weight at 105 °C, and then, the amount of biomass was determined. To
determine the chemical composition, the plant material was ashed in a
chamber furnace at 450 °C for 12 hours, and the residue was dissolved in
diluted (1:2) (v/v) nitric acid. The contents of the studied trace
elements were determined by inductively coupled plasma optical emission
spectrometry (ICP-OES, Perkin Elmer Optima 7300 DV, Waltham, USA)
(Oleszczuk et al., 2007).