HRISTEVA, Ts., M. YANEV, Hr. BOZUKOV and Sht. KALINOVA, 2015. Condition of soil microbial communities when exposed to some chloroacetamide herbicides. Bulg. J. Agric. Sci., 21: 730–735
In the process of tobacco growing, during field tests, scientists studied the impact of chloroacetamide herbicides Butizan S (а.s. metazachlore) and Dual Gold 960 EK (a.s. S-metolachlor) on soil microbial communities. They determined dynamically the population density of trophic groups of microorganisms, which are indicators for the general sanitary condition of the soil. A suppression in the numerical development of ammonifying and immobilizing mineral nitrogen microorganisms was found. This was achieved without disturbing the mineral nutrition of tobacco plants. An increase was recorded in the spores and in the relative proportion of spore-like microorganisms, which indicates degraded life conditions in the soil. Metolachlor has a negative impact with a longer duration. The likely period of adaptation in microbial communities after treatment is about 15 days for Butizan S (а.s. metazachlore) and 35 days for Dual Gold 960 EK (a.s. S-metolachlor). The stimulation effect on the group of Actinomycetes and the changes in their dynamics defines them as the first biodegrading agents in both herbicides, followed by the ammonifying microorganisms.