The influence of fertilisation and crop rotation on soil microbial characteristics in the long-term field experiment
Soils were sampled from the plots with four variants of fertilisation: Nil – without fertilisation, NPK – mineral fertilisation, FYM – farmyard manure, FYM + NPK – farmyard manure with mineral fertilisation, and two variants of crop rotation: field IV – classical 9-year crop rotation, field B – 2-year rotation of alternative growing. Determination of urease, CFU of <I>Azotobacter</I> spp. and potential nitrogenase activity was conducted during the period 1999–2004. The urease activity was positively affected by manure fertilisation (FYM) and by the combination of FYM + NPK. The statistically significantly highest counts of <I>Azotobacter</I> spp. and the highest nitrogenase activity were determined on field B in variants FYM and FYM + NPK. The results show that there was a higher amount of accessible nitrogen present on field IV than on field B. This might explain the lower counts of <I>Azotobacter</I> spp. and therefore the lower nitrogenase activity. According to our results, activity of urease, CFU of <I>Azotobacter</I> spp. and potential nitrogenase activity are very closely connected with N inputs.