Dynamics of Changes in Microorganisms in Rhizosphere Zone of Lawn Grasses in the Second Year After the Application of Sewage Sludge

The aim of the study was to present the dynamics of changes in the number of selected microorganisms in the rhizosphere zone of grasses two years after the application of sewage sludge. The study was conducted on four specially prepared research plots along the main roads in Bialystok. Three doses of sewage sludge were applied: 0 (control), 7.5 and 15 kg/m². Then the plots were seeded with two mixtures of lawn grasses: Eko and Roadside. Samples of roots with soil were collected three times during the vegetation period of 2012 (April, July and October) and assayed for the total number of bacteria, the number of Gram-negative bacteria, the number of Pseudomonas fluorescens, the number of amylolytic and proteolytic bacteria. Microbiological tests of the rhizosphere showed seasonal variations of all investigated microbiological parameters. The greatest average of the total number of bacteria, Gram-negative bacteria and proteolytic bacteria was observed on the plots in April, amylolytic bacteria in July while in the case of Pseudomonas fluorescens was observed on the plots in October. The time of measurement had the biggest impact on the number of microorganisms. An increased number of microorganisms was observed on all plots in April. Whereas, the fertilization with sewage sludge and grass mixtures did not affect the microbiological parameters.