In this experiment the effect of chromium (VI) applied at doses of 0, 40, 80 and 120 mg.kg(-1) of soil on the growth and development of oats, and on the presence of the following bacterial groups: copiotrophic, oligotrophic, nitrogen fixing, Azotobacter sp. as well as actimycetes and fungi. Activity of some soil enzymes were also determined i.e.: dehydrogenases, urease, acid and alkaline phasphatases. An attempt to diminish negative impact. of chromium on soil and crops was made by the addition of barley straw to the soil. The experiment was performed on loamy sand of value pH in 1M KCl of 6.6. Studies were performed in bare soil or with oats cover cv. Komes in two experimental series with and without straw amendment.

In the result of studies it was found that hexavalent chromium applied at doses of 80 and 120 mg.kg(-1) of soil significantly inhibited growth and development of oats. Chromium adverse effects on activity of soil dehydrogenases, urease and acid and alkaline phosphatases and the number of Azotobacter sp. and actinomycetes, whereas stimulation of the proliferation of oligotrophic, copiotrophic, ammonifers and nitrogen fixing bacteria was observed. Soil amendment with straw resulted in enhanced activity of all studied enzymes and abundance of majority of studied microbial communities. It also diminished toxic effects of applied chromium.