Influence of crop species on quantity and physiological activity of rhizosphere microorganisms
I. M. Malynovska, V. M. Yula, N. M. Asanishvili, M. M. Ptashnik, A. H. Lyubchich
Goal. Study of the number and physiological activity of the main trophic and systematic groups of microorganisms. Results. We registered that the rhizosphere soil under soybean plants had the maximum number of microorganisms associated with the transshipment in the root secretions of legume amino acids and amines. When soybean is grown on an intensive agricultural background, denitrifiers' physiological and biochemical activity is maximal. Among the studied cultures, their abundance is also maximal. In the corn rhizosphere, a minimal number of denitrifiers with a low physiological and biochemical activity are 8.2 times less than the physiological-biochemical activity of the row-spacing microorganisms that indicates the synthesis of substances with inhibitory properties of this culture relative to the denitrification process's pathogens. In the soil with extensive farming, the Azotobacter number considerably exceeds the indices of intensive-farming agrozem: when growing corn - in 3.26 times, wheat – 4.28, flax – 2.08, soya – 3.29, row-spacing – 4.05 times (organic and mineral fertilizers have not been introduced since 1987). This indicates the impossibility of using this indicator, as a diagnostic indicator, to sufficient soil fertility level. The number of polysaccharides synthesizing microorganisms in most crops' rhizosphere is higher when grown on an intensive agricultural background, except for winter wheat, in the rhizosphere of which the higher abundance of polysaccharide synthesizing microorganisms is shown on an extensive agricultural background. Conclusions. We established that the number and biochemical activity of microorganisms in soil depend on the type of crop and varies when growing plants on agricultural backgrounds of different intensity. We registered that in the rhizosphere of leguminous plants, the mineralization of humus slows down compared to cereal crops. The intensity of consumption of organic matter and humus is higher when growing the studied crops on an extensive agricultural background, the activity of mineralization of nitrogen compounds, on the contrary, when growing on an intensive agricultural background. The soil of soybean rows characterizes the minimum phytotoxicity, and the maximum is the soil of row-spacing and rhizosphere of wheat. Thus, we confirmed long-standing observations concerning the greater phytotoxicity of the rhizosphere with cereals than legumes.
Keywords: microorganisms, ecotrophical groups, nitrogen mineralization, humus mineralization rate, soil phytotoxicity, maize, wheat, soybean, agricultural background.
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