Activitatea respiraţiei din comunităţile microbiene ale cernoziomului arat din Republica Moldova

The respiration activity of the microbial communities in the plowed chernozem was evaluated in fractions of the values of basal respiration (BR), substrate-induced respiration (SIR), as well as of specific respiration (qCO2), in relation to the soil of the natural biocenosis (standard). For study a carbonate chernozem from a field cultivated with maize in a seven-course crop rotation system was used. The investigations were carried out on the following experimental variants: 1) control (no fertilizing); 2) N60P45К45; 3) N160P120K90; 4) farmyard manure 12 t/ha+P15; 5) farmyard manure 24 t/ha+P30; 6) farmyard manure 12 t/ha+N60P45K45. The uncultivated soil from a natural biocenosis situated in the vicinity of experimenttal plots served as reference background. It was established that agricultural use of soil not only modified the values of BR and SIR but their ratio as well. The average absolute values of basal respiration and substrate-induced respiration were 0,71–1,16 μg C - CO2/g sol/h in the plowed soils and 10,3–25,9 μg C - CO2/g sol/h in the uncultivated soil. Absolute indices of BR from the plowed soil variants were less than SIR values. At the same time the relative values of BR (against uncultivated soil) exceeded the relative values of SIR by 10-21%. The specific respiration indices (qCO2) (1.99-3.07 μg C-CO2/mg Cmic/h) generally reflected the steady state of the microbial communities in the studied variants, but also indicated that between BR/microbial biomass ratios of the plowed variants and BR/microbial biomass ratio of the soil of natural biocenosis a difference was formed that was conditioned by the prolonged influence of anthropic factors. This difference characterizes as stressful the state of the microbial communities, and its amplitude (13–54%) denotes the degree of stress.