The aim of this study was to evaluate the effect of two types of multi-walled CNTs: raw MWCNTs and carboxylated MWCNTs, on the microbiology of soil on which three species of fodder grasses were cultivated: timothy grass, common meadow grass and meadow fescue. A two-year pot experiment evaluated the effect of MWCNTs (at a dose of 15 g pot-1, i.e. 4.77 t ha-1) and carboxylated MWCNTs (at a dose of 80 g pot-1, i.e. 25.5 t ha-1) on the number of microorganisms in soil and in root matter. The total number of bacteria, number of dormant bacteria, actinomycetes and fungi were investigated. Considerable diversity in the counts of microorganisms was observed, depending on a grass species, type of fraction and type of nanotubes added. When analyzing the total results from the three fractions (the rhizosphere, outside the rhizosphere and roots), the highest number of most of the microorganisms studied was determined in samples from control treatments. The lowest values were obtained in samples from treatments with the addition of carboxylated MWCNTs, and intermediate values were achieved from treatments with raw MWCNTs. The total number of bacteria was positively correlated with the number of dormant bacteria, actinomycetes and fungi. The number of dormant bacteria correlated with the growth of actinomycetes and fungi. Soil contamination even with relatively high amounts of MWCNTs or carboxylated MWCNTs does not cause massive mortality of soil microorganisms. That is why it is important to assess their potential effect on the environment.  

24.1.2019