The objective of this research has been to determine the impact of soil contamination with fluorine, including the concomitant application of substances neutralizing this pollution, on counts of actinomyces, fungi, and copiotrophic bacteria, and on the activity of acid phosphatase, alkaline phosphatase, grease, and dehydrogenase. The research was based on two pot experiments, both conducted in 2009 in a greenhouse at the University of Warmia and Mazury in Olsztyn, Poland. One experiment involved winter oilseed rape, while the other was performed on maize followed by yellow lupine. The following factors were included in both experiments:
I) increasing doses of fluorine in the form of potassium fluoride (0, 100, 200, 300 mgF·kg^-1 of soil)
II) substances neutralizing soil pollution with fluorine: lime, in a dose corresponding to 1 Hh of soil, charcoal, and loam – both in amounts equal to 3% of the soil mass per pot.
The biological activity of soil was assayed after harvesting winter oilseed rape (BBCH 69) and yellow lupine (BBCH 69).
It has been demonstrated that low doses of fluorine (from 100 to 200 mgF·kg^-1 of soil) had a positive influence on counts of the analyzed microorganisms and on the activity of the examined soil enzymes. Under the influence of such low amounts of fluorine, the number of actinomyces and the activity of urease increased in soil tested after the harvest of winter rape and yellow lupine, the latter being a catch crop sown after maize. The neutralizing substances had a much better effect on counts of the analyzed microorganisms than on the activity of soil enzymes. The counts of actinomyces and copitrophic bacteria were positively affected by all the substances added to soil, as compared to the control treatments. With respect to fungi, these microorganisms responded positively only to the application of charcoal and loam to soil cropped with yellow lupine. In general, the tested substances had a beneficial influence on the activity of acid phosphatase and urease. As regards the activity of alkaline phosphatase, it was adversely affected by the neutralizing substances. The residual effect of fluorine on counts of the analyzed microorganisms and activity of the soil enzymes was milder in the soil sampled after the harvest of yellow lupine, which seems to indicate that fluorine loses its toxic properties with time.