In this paper, the influence of soil contamination with heavy metals (cadmium and mercury) on nitrogen content in Miscanthus x giganteus leaf, was determined. The paper is based on estimates of biomass quantity and nitrogen content in leaf tissue using remote sensing that make up non-destructive methods such as proximal VNIR spectroscopy. It serves as an additional tool with analytical methods that integrate physiological and optical properties, and as a result the state of plant tissue is obtained, i.e. the influence of heavy metals or other stressors on the concentration of plant pigments and nitrogen content. The aim of the study was to determine effects of cadmium and mercury on miscanthus using proximal spectroscopy in the visible and near-infrared (VNIR) region of the electromagnetic spectrum by monitoring nitrogen content in the leaf and aboveground biomass yield as one of the main parameters. The effect of cadmium and mercury differed depending on the treatments of different soil improvers to which miscanthus seedlings were exposed in experimental pots inside an open greenhouse. Leaf reflection was measured on 24 samples at the end of the 2018./2019. and 2019./2020. vegetation seasons with a transmission spectroradiometer in the wavelength range of 350─1050 nm. The yield of aboveground biomass was determined by weighing, while the content of total nitrogen in the leaf was determined by the method of dry incineration. Partial least squares regression (PLSR) was used to display and process the results, which determined a strong correlation for the aboveground biomass yield (R2 = 0.53; RMSE = 0.833 t/ha), and a complete correlation was found for the composition of the total nitrogen content in the leaf (R2 = 0,87; RMSE = 0,139%). In terms of treatment, sewage sludge showed the greatest contribution in the total nitrogen content in the aboveground biomass of miscanthus, while the ash proved to be the least useful improver in the first year of cultivation, and soil without amandments and mycorrhiza in the second year of cultivation.