The aim of this study was to investigate the effects of various chemicals used in cultivation of winter rapeseed on the abundance of some groups of microorganisms and their biochemical activity in soil.

The investigations on the impact of the chemical agents (Roundup 360 SL, Reglone 200 SL, Basta 150 SL, Avans Premium 360 SL, Spodnam 555 SC, Caramba 60 SL) applied for desiccation of rapeseed on the microbiological and biochemical soil properties were conducted in two field experiments and a pot experiment. Soil was sampled for analyses eight times during the three years of the experiment from the arable layer of each plot, i.e. immediately after winter rapeseed harvest(early August), and next after 2, 10, 12, 14, 22, 24 and 26 months of the experimental period. The experiment no 1 comprised the following objects: soil without chemicals, soil + optimal dose of Roundup 360 SL, soil + 10% higher dose of  Roundup 360 SL, soil + optimal dose of Reglone 200 SL, soil + 10% higher dose of  Reglone 200 SL. The experiment no 2 comprised the following objects: soil without chemicals, soil + optimal dose of Avans Premium 360 SL, soil+ optimal dose of Spodnam 555 SC, soil + optimal dose of Caramba 60 SL.

            The pot experiment was established on soil from the class of black earths formed from light clay loam. The aim of the three-factor pot experiment was to investigate the impact of the Roundup 360 SL and Reglone 200 SL agents as well as the dose and duration of the experiment on soil microbial and biochemical activity. Both herbicides were applied to the soil in the form of aqueous emulsion in doses recommended by the manufacturer (optimum doses) and 10-, 50-, and 100-fold increased doses. Soil without addition of the herbicide was the control. Microbial analyses both field experiments comprised determination of the following: total number of bacteria, total number of fungi, number of bacteria with proteolytic capabilities, number of bacteria with proteolytic capabilities. Biochemical analyses on field experiments included determinations of acid and alkaline phosphatase activity. On pot experiment analyses included determinations of dehydrogenase, protease, urease, acid phosphatase, alkaline phosphatase, amonification and nitrification intensity and respiratory activity of the soil. Chemical analyses included determination of the content of organic C, total N and the soil pH.

The present investigations showed that contamination of soil with the Roundup 360 SL, Reglone 200 SL, Basta 150 SL, Avans Premium 360 SL, Spodnam 555 SC, and Caramba 60 SL plant protection products led to disturbances in the microbial abundance and enzyme activity. The soil microorganisms and processes carried out by them were characterised by varied sensitivity to the plant protection products applied to the soil. The impact of all the chemical agents on the examined microbial groups and soil biochemical properties was determined by the type of the chemical applied as well as its dose, analysis stage, and the type of the microbiological and biochemical indicator. The plant protection products tested are characterised by a long-term effect on the analysed microbial groups, soil enzyme activity, and the intensity of biochemical processes.