Impact of agricultural land use on distribution of microbial biomass and activity within soil aggregates

The presence of aggregates of various sizes in the soil is an important condition for soil carbon sequestration. In this system, microbial biomass is a key link. This work was devoted to the study of the influence of land use systems on the distribution of SOC, MB-SIR, microbial activity and eco-physiological indices (qCO(2), QR, MB-SIR/SOC and qCO(2)/SOC) in relation to the size of soil aggregates. The distribution of SOC, MB-SIR and mineralization activity among the aggregates was heterogeneous. In the soil of crop rotation, high mineralization activity and MB-SIR were found in the aggregates 0.5-0.1 mm, in the monoculture soil in aggregates <0.1 mm and in the control soil in the aggregates 1-0.25 mm. There was a general trend towards a decrease in microbial activity, MB-SIR and SOC availability with an increase in aggregate size. In agricultural soils, microbial activity was determined by large aggregates (>5 mm), while in the control soil, by the aggregates 5-1 mm. Depending on the type of site and the size of aggregates, the differences in microbial metabolism were revealed. The qCO(2) and QR values decreased, and the MB-SIR/SOC and qCO(2)/SOC increased in the series: control soil > crop rotation > monoculture. In the control soil, the values of the eco-physiological indices decreased with decreasing aggregate size. And vice versa, in agricultural soils, these parameters were the highest in the microaggregates (<0.25 mm). The monoculture soil, in contrast to the control soil and crop rotation soil, turned out to be more energy efficient.