Effect of Composition and Properties of Soils and Soil-Sand Substrates Contaminated with Copper on Morphometric Parameters of Barley Plants

In a multifactor vegetation experiment, the effect of composition and properties of soils and soil-sand substrates contaminated with various doses of copper acetate on the morphometric parameters of spring barley seedlings was studied. It has been shown that germination and seed germination energy, as well as the length of roots, aboveground parts, and dry biomass of plants depend in a complex way on the concentration of Cu in soils and substrates, as well as on their buffering capacity to heavy metals. Two mechanisms of Cu influence on plant development have been revealed, i.e., metabolic at С Cu ≤ 500 mg/kg of soil and diffusional at С Cu ≥ 500 mg/kg. Using the methods of regression analysis of experimental data, a multiple regression equation has been obtained that combines the morphometric index of plants, the concentration of Cu in substrates, and the buffering capacity of soils to Cu. On its basis, in the soil buffering capacity–Cu concentration coordinates, a curve of values of the maximum permissible concentrations of Cu in soils was built on a plane in the range from 17 to 2047 mg/kg. It permits us to separate the zone of permissible development of barley plants (a decrease of the morphometric index by 15%) from the zone of exceeding the accepted values of the maximum permissible concentration of Cu. Thus, the maximum permissible concentration is considered to be a function of Cu concentration, the soil buffering capacity to heavy metals, and plant species rather than a fixed value.