Occurrence of Azotobacter Spp. in Some Polish Soils

In the year 2000 the occurrence of Azotobacter spp. in 31 Polish soils was examined and results of this study were compared with those published by Ziemięcka for 28 soils analysed in 1917-18. Almost 52 % of the soils tested in 2000 were colonised by Azotobacter spp. indicating that intensification of agricultural practices that took place during the past century has not significantly changed (50 % soils with Azotobacter examined in 1917-18) the colonisation of Polish soils by the studied bacteria. When present, numbers of these bacteria varied widely, from several (soils No. 17 and 31) to almost 10,000 cfu g-1 of the soil No. 25.