POLLUTION OF SOIL WITH HEAVY METALS WHILE GROWING PERENNIAL GRASSES
Authors: Tkachuk Oleksandr 
Published: September 2020

Total arable land in Ukraine amounts to 32.4 million hectares, about 2.6 million hectares or 8% is from soils contaminated with heavy metals. The widespread distribution of such soils and the subsequent chemicalisation of crop and agriculture lead to disruption of agrocenoses. The situation is complicated by the accumulation of more than one heavy metal at the same time in the soil. In such a condition, a synergistic effect is shown in relation to the soil biota - an increase in toxic effects. This requires finding ways to reduce soil poisoning by heavy metals on an environmental footing. The purpose of the article is to study the influence of growing perennial grasses on the total contamination of soil with heavy metals.
Field research was conducted during 2013 – 2018 at the Agricultural Research Institute of the Vinnytsia National Agrarian University. Soil on the experimental site
– gray medium loam. The effect on the change in the total soil contamination by heavy metals of six species of legumes of perennial grasses were studied: alfalfa sowing (Medicago sativa I.), meadow clover (Trifolium pratense L.), sand aspartate (Onobrychis arenaria Kit.), White turmeric (Melilus albus L.), the horned (Lotus corniculatus L.) glacier, and the eastern goat (Galega orientalis Lam.). The determination of the content of gross and mobile forms of heavy metals in soil: lead, cadmium, copper and zinc was performed by atomic absorption spectrophotometry according to DSTU 4362:2004, DSTU 4770 (2, 3, 9):2007. According to standardized methods, the coefficient of concentration of heavy metals in the soil and the total index of soil contamination with heavy metals were calculated.
Growing sand aspartame for two years reduced the concentration of lead in soil by 74.8%, horned glacier – 60.6%, clover meadow – by 49.5%, white clover – by 39.4%, alfalfa sowing – by 4.0%. At the same time, the two-year-old eastern goat cultivation did not affect the change in the concentration of lead in the soil. After two years of growing sand aspartame, the cadmium concentration ratio decreased by 96.5%, after clover meadow – by 94.2%, alfalfa sowing – by 90.7%, and horned glacier – by 16.3%. After two years of growing white clover and goat eastern, the coefficient of cadmium concentration in the soil did not change. After two years of cultivation of sand aspartame, the coefficient of copper concentration in the soil decreased by 11.9%, after white – by 5.7%, goat eastern – by 4.4%, glacier-horned – by 3.1%, clover meadow – by 1.3% and after the cultivation of alfalfa sowing, the coefficient of copper concentration in the soil did not change. The two-year cultivation of sand aspartame helped to reduce the zinc concentration ratio by 67.5%, the growth of horned lollipop – by 55.0%, of white clover – by 52.5%, of eastern goat – by 40.0%, of clover meadow – by 27.5%. At the same time, growing alfalfa sowing for two years does not change the zinc concentration factor in the soil.
Four-year cultivation of sand aspartic helps to reduce the concentration of lead in soil by 74.8%, four-year cultivation of goat eastern – by 55.6%, glacial horn – by 42.4%, alfalfa sowing – by 39.4%. Four-year cultivation of alfalfa sowing reduces the concentration of cadmium in the soil by 96.5%, compared with the two-year cultivation of alfalfa sowing, and the rest of herbs – by 97.7%. During the four years of vegetation of alfalfa sowing and goat eastern the coefficient of concentration of copper in the soil decreases by 98.2%, the horned glacier – decreases by 96.9%, aspartame sand – by 93.8%. Four years of horned glacier cultivation reduces the concentration of zinc in soil by 90.0%, four years of cultivation of alfalfa sowing and goat grazing – by 87.5%, and aspartic sand by 72.5%.
The two-year cultivation of all the studied legumes of perennial grasses reduced the total indicator of soil contamination by heavy metals. In particular, after two years of cultivation of sand asparagus, it decreased by 2.11, after growing clover meadow – by 1.44, horned gluten – by 1.03, alfalfa sowing – by 0.82, eastern goat – by 0.26. In the four-year period of cultivation of sand aspartame, the total indicator of soil contamination by heavy metals decreased by 4.00, after four years of cultivation of the Eastern goat – by 3.97, of the horned glacier – by 3.82, of alfalfa sowing – decreased by 3.80.
Key words: heavy metals, soil, total pollution, perennial legumes.