Dependence of agro-environmental soil constitution on potassium balance in agrocenosis

The studies conducted during a long-term field experiment showed that self-supporting potassium balance in agrocenosis improved essentially both agrochemical and environmental state of the soil and agrocenosis as a whole. Optimization of soil potassium status at sufficient level of nitrogen and phosphorus favored an increase in crop capacity of growing cultures and efficient use of nutritive elements by plants. Prolonged application of increasing doses of potassic fertilizers did not influence negatively on soil agrochemical properties as compared to N-background: soil exchange capacity and acidity practically did not change, as for humus content it increased to some extent. The level of soil potassium influenced, to some degree, soil nitrogen regime regulating the processes of fixation and mobilization of ammonium and the scale of consumption of nitrate nitrogen. The intensity of the use of potassic fertilizers most greatly influenced the composition of soil cations: the content of soil magnesium and especially calcium decreased considerably when applying elevated doses of potassium. Different intensity of use of mineral fertilizers in agrocenosis had an effect on functioning of soil microbial communities. Systematic application of science-based doses of fertilizers had a positive effect on the number and structure of soil microbiocenosis. Optimization of effective soil fertility and condition of mineral nutrition of plants in agrocenosis favored a considerable increase in the number of soil bacteria and actinomyces. Deficiency of movable forms (at least of one of macroelements, for example, potassium) had a negative effect on populations of prokaryotes. One-sided use of nitrogenous fertilizers at serious deficiency of potassium and scanty potassic fund of soil caused a strong growth of populations of soil fungi, including phytopathgenous ones, increasing soil infectious potential at the same time. Optimization of soil potassic state favored a considerable decrease in the number of soil fungi and improvement of phythosanitary situation in agrocenosis. The number of different groups of soil microorganisms and structure of the whole of microbiocenosis is an informative index of assessment of agro environmental state of ploghlands reflecting both the level of soil effective fertility and soil infectious potential.

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