TRACE ELEMENTS IN THE AGROCENOSIS OF A PEAR ORCHARD DURING BIOLOGIZATION
Authors: Klimenko O. , Novickaya A. , Yakusheva N. , Struchenko A. , Fedyahin I. 
Published: October 2024

The data of a two-factor field experiment conducted to research the content and mutual influence of trace elements (TEs) in soil, segetal vegetation, cultivated grasses and pear plants during the biologization of agrocenosis are presented. The experiment was carried out in the valley of the Salgir River in central Crimea (Simferopol region) on meadow alluvial carbonate soil in the orchard of pear (Pyrus communis L.) cv. Tavricheskaya on the rootstock VA 29. The experiment focused on the influence of the «sod» factor: 1) natural sod of the soil by segetal vegetation (SV) – control; 2) a mixture of herbs: Lolium multiflorum Lam. + Medicago sativa L. (HM2); 3) a mixture of herbs: L. multiflorum + M. sativa + Festuca pratensis Huds. + Trifolium pratense L. + Bromus inermis Leyss (HM4). Additionally, the effect of microbial preparations (MP) was investigated, which included: 1) a control group without MP, 2) Azotobacterin 07-Agro – the nitrogen-fixing and growth-stimulating agent; 3) Microbiocom-Agro (MBC) is a complex fertilizer with nitrogen-fixing, growth-promoting, phosphate-mobilizing, and biological protective properties. Mobile (available) forms of TEs: Fe, Mn, Cu, Zn and Co in soil, and total forms of the same elements in grasses and pear leaves were determined using the atomic absorption method. It was revealed that the concentrations of Fe, Mn and Co in the soil were below the regional background levels, while Mn and Co were at levels that were considered to below for fruit crops. The content of Cu and Zn in the soil was high, but did not exceed the maximum permissible concentration and was located in the following order: Mn ˃ Zn ˃ Fe ˃ Cu ˃ Co. Biologization caused an increase in the mobility of TE. MBC, when applied in combination with CT4, contributed to some relatively greater accumulation of Zn relative to Mn in the soil. It may cause Mn deficiency in the pear plant. The content of total forms of ME in herbs was generally optimal or high, but Mn was low. According to their content in herbs, TEs are arranged in the order: Fe ˃ Cu ≥ Zn ˃ Mn ˃ Co. The lack of Mn in grasses is associated with a deficiency of this element in the soil. MPs contributed to the accumulation of TEs in the biomass of sown grasses (except for Mn), which can be used for phytoremediation of soils contaminated with Co and Zn. The Mn content in herbs decreased under the influence of MBC. The concentration of total forms of TE (excluding Mn) in pear leaves was optimal and high, while Mn level was low. The series of element ratios was similar to that obtained for grasses, but Zn content in pear leaves was higher than Cu. The applied biologization methods increased the contents of Fe, Zn, and Co in leaves and decreased the concentration of Mn below the optimal level for pears. Herbs competed with the fruiting plants in the absorption of TEs, especially when their biodiversity increased and in combination with MPs. During the process of biologization the absorption of Co by the pear increased significantly and the absorption of Mn decreased, which caused a lack of the latter in the pear nutrition, both due to its low content in the soil and antagonism with Fe, Zn, Cu and Co in the plant. This manifested itself in external symptoms of deficiency, such as weak chlorosis and necrosis of young pear leaves. In general, the use of AB in conjunction with HM2 is the more optimal combination of sod and MP (from those studied) in terms of its effect on soil properties and nutrition of pear plants. A research should be conducted to determine optimal doses of manganese fertilizers for application through foliage for specific environmental conditions in order to improve the nutrition of pear by Mn at a low content of its mobile forms in carbonate soils and during biologization.