Daily dynamics of the number and activity of nitrogen-fixing bacteria in fallow and intensely cultivated soils

The daily dynamics (during 33 days) of the number (colony-forming units (CFU)) of nitrogen-fixing bacteria and of the nitrogen-fixing activity (the acetylene method) were determined in a gray forest soil under a fallow land and under an intensely cultivated field. The daily dynamics of the CFUs determined on the nitrogen-free medium in the samples from both plots had wavelike patterns. The daily values of the actual and potential activities of nitrogen fixation in the samples from the fallow land plot and of the actual activity of nitrogen fixation in the samples from the intensely cultivated soil were low and close to the detection limit. The potential activity of nitrogen fixation in the intensely cultivated soil was significant and also had a wavelike pattern. The harmonic analysis of the daily dynamics of the CFUs and nitrogen fixation showed the statistically significant harmonics of these biological characteristics pointing to the objective and regular character of the wavelike dynamics. The revealed dynamics of the biological characteristics of the soils and the methods of their analysis are important in terms of the comparative study of the biological properties of different soils.