The Effect of Diflufenican and Its Mixture with S-metolachlor and Metribuzin on Nitrogenase and Microbial Activity of Soil under Yellow Lupine (Lupinus luteus L.)

The aim of the study was to evaluate the effect of the active substance of diflufenican and its combination with s-metolachlor or metribuzin, applied to yellow lupine, on the nitrogenase activity, the population size of selected groups of microorganisms, the activity of soil enzymes and their sensitivity to the tested preparations. All analysed preparations caused a reduction in the total number of bacteria and the number of actinobacteria and oligotrophic bacteria at the beginning of the vegetation period of yellow lupine. In the combination where diflufenican was used separately a stimulatory effect on nitrogenase activity was observed. The research revealed very high sensitivity of dehydrogenases and acid phosphatase to the soil contamination caused by application of all the tested herbicides. The dehydrogenases activity values were closely correlated with reduced populations of the groups of microorganisms. Diflufenican applied separately caused a relatively small negative effect on biological soil properties and consequently could have a smaller negative effect on soil environment contamination in comparison to other variants.