Number of Microorganisms in the Soil Cultivated with Legume-Grass Mixtures Supplied with Phytohormones and Nitrogen

The study concerned the number of microorganisms colonizing the humus layer and under plough soil from the cultivation of perennial ryegrass mixtures with red clover, which were fed by biostimulant based on the phytohormones and different doses of nitrogen. Nitrogen was applied at four levels-control (no nitrogen), 50, 100 and 150 kg N∙ha-1, biostimulant in two combinations - with and without preparation. Soil material to assess the size of individual groups of microorganisms was collected from each experimental plot in autumn 2010 from the humus (0-20 cm) and under plough layers (20-40 cm). The analysis of soil samples for a total number of bacteria, actinomycetes and fungi was conducted at the Department of Agricultural Microbiology IUNG-PIB in Pulawy. Results of studies have shown that more colonies of bacteria, actinomycetes and fungi were colonized the humus horizon. Biostimulant application in this cultivation led to a decrease of the total number of colonies of the all soil microorganisms groups but improved the ratio of bacteria to fungi. Increasing doses of mineral nitrogen by the limiting of the bacteria number and intensive development of soil fungi, helped to narrow the B/F ratio.