The effect of the pesticide delivery method on the microbial community of field soil.

The study deals with the effects of herbicides (metribuzin, tribenuron-methyl, fenoxaprop-P-ethyl) and fungicides (tebuconazole, epoxiconazole, azoxystrobin) applied to soil as free pesticides or as slow release formulations embedded in a biodegradable composite matrix on the structure of the soil microbial community. The matrix consisted of a natural biopolymer poly-3-hydroxybutyrate [P(3HB)] and a filler-one of the natural materials (peat, clay, and wood flour). The soil microbial community was characterized, including the major eco-trophic groups of bacteria, dominant taxa of bacteria and fungi, and primary P(3HB)-degrading microorganisms, such as Pseudomonas, Bacillus, Pseudarthrobacter, Streptomyces, Penicillium, and Talaromyces. The addition of free pesticides adversely affected the abundance of soil microorganisms; the decrease varied from 1.4 to 56.0 times for different types of pesticides. The slow release pesticide formulations, in contrast to the free pesticides, exerted a much weaker effect on soil microorganisms, no significant inhibition in the abundance of saprotrophic bacteria was observed, partly due to the positive effects of the composite matrix (polymer/natural material), which was a supplementary substrate for microorganisms. The slow release fungicide formulations, like the free fungicides, reduced the total abundance of fungi and inhibited the development of the phytopathogens Fusarium and Alternaria. Thus, slow release formulations of pesticides preserve the bioremediation potential of soil microorganisms, which are the main factor of removing xenobiotics from the biosphere.