THE INTENSITY OF THE ACCUMULATION OF HEAVY METALS IN SOIL AND GRAIN DEPENDS ON THE REPETITION OF MAIZE CULTIVATION
Authors: Tkachuk Оleksandr , Bondarenko Mykhailo 
Published: December 2024

In most farms that use intensive crop cultivation technologies, corn makes up 40% of the sown area structure. And this, in turn, can lead to its re-growing. The saturation of short-rotation crop rotations with corn in farms is more than 30%, which is three times higher than scientifically based calculations. Therefore, with such a share of corn in the crop rotation, part of its area is sown again in the same field. Corn tolerates repeated cultivation on the same field for three to four years. But under such conditions, in order to guarantee high and stable corn yields, it is necessary to increase the application rates of mineral fertilizers and strengthen the chemical protection of crops against harmful organisms. Scientific evidence indicates that maize in a monoculture requires 35-55 kg/ha more nitrogen than that grown after a better predecessor. With such intensive fertilization of repeated crops of corn with mineral fertilizers, toxic substances contained in fertilizers may accumulate in the grain. A high risk of accumulation of heavy metals: lead, cadmium, copper and zinc, which are present in mineral fertilizers. The purpose of the research is to study the intensity of accumulation of heavy metals in the soil and grain during repeated cultivation of corn in the same field. Laboratory studies were carried out in the certified and accredited laboratory of the Vinnytsia branch of the Institute of Soil Protection of Ukraine of the Derzhgruntokhorona State University. The content of heavy metals in soil and grain was determined: lead, cadmium, copper and zinc. During the repeated cultivation of corn, to ensure a high and stable yield of its grain, the rate of mineral fertilizers was increased by 30%: from N45P45K45 to N65P65K65. With such an increase, the content of mobile forms of lead in the soil increases by 4.2 times, but the content of mobile forms of cadmium decreases by 10%, copper by 19.6%, and zinc by 23%. Exceeding the maximum allowable concentration of heavy metals in the soil was not detected in any variant. We found that when corn was re-grown on the same plot, the content of copper as a trace element decreased by 19.6%, and zinc by 23.0%. Such a decrease in the content of microelements in the soil indicates the unidirectional absorption of these substances by corn plants during two years of cultivation and requires compensation of these elements in the form of microfertilizers. During repeated cultivation of corn, the content of lead in its grain decreased by 8.2%, cadmium - by 14.3%, copper - by 2.0%, zinc - by 24.8%. Exceeding the MPC of lead in corn grain during its one-time and repeated cultivation with a value of 1.7 MPC and 1.6 MPC, respectively, was established. During one-time cultivation of corn, the coefficient of accumulation of lead and cadmium in its grain was 4.6 times and 4.3% higher, respectively, than during two-time cultivation, zinc - by 2.4%, and copper - on the contrary, it was higher than during two-time cultivation of corn by 17.9%. The total rate of heavy metal contamination of the soil during repeated cultivation of corn was 16.5% higher than during one-time cultivation, but was at a safe level. In the grain of repeated cultivation of corn, the total indicator was 2.2 times lower than that of one-time cultivation.