Cilj istraživanja bio je primjenom digitalnog mikroskopa utvrditi utjecaj i dinamiku učinka različitih koncentracija herbicida pendimetalina na rast bakterije Bradyrhizobium japonicum. Istraživane koncentracije pendimetalina iznosile su 0,00; 0,165; 0,33; 0,66; 1,32 i 2,64%. Koncentracija 0,66% odgovara količini pendimetalina koja se uobičajeno primjenjuje u praksi (registrirana dozacija). Utjecaj pendimetalina na rast bakterija utvrđivan je mjerenjem širine zone inhibicije oko filter-diskova tretiranih istraživanim koncentracijama pendimetalina 5, 7, 10 i 12 dana nakon nacjepljivanja (DNN) bakterija na hranjivu podlogu. Najmanji inhibitorni učinak utvrđen je kod prvog mjerenja (5 DNN), kad se prosječna širina zone inhibicije kretala od 0,18 mm kod najniže (0,165%) do 0,97 mm kod najviše (2,64%) istraživane koncentracije. Pri svakom sljedećem mjerenju utvrđena je progresija inhibitornog učinka pendimetalina na rast bakterija. Najveći inhibitorni učinak utvrđen je kod posljednjeg mjerenja (12 DNN) kad je širina zone inhibicije kod koncentracije pendimetalina od 0,165% iznosila 0,61 mm. Povećanjem koncentracije znatno se povećavala, te je kod koncentracije od 2,64% iznosila 2,46 mm. Rezultati istraživanja ukazuju na negativan učinak herbicida pendimetalina na rast bakterija B. japonicum čak i kod koncentracija manjih od preporučene koja se primjenjuje u praksi.; The objective of this study was to determine the effect of different concentrations of herbicide pendimethalin on the growth of nitrogen-fixing bacteria Bradyrhizobium japonicum using a digital microscope. Pendimethalin was applied at concentrations of 0.00; 0.165; 0.33; 0.66; 1.32 and 2.64%, where the concentration of 0.66% presents the amount of herbicide which is usually applied in the field (recommended dose). The influence of pendimethalin on the growth of B. japonicum was determined by measuring the width of the inhibition zone around the discs 5, 7, 10 and 12 days after inoculation (DAI) of bacteria on a nutrient medium. The lowest inhibitory effect of pendimethalin for all concentrations determined was 5 DAI, when the average width of inhibition zone was between 0.18 mm for the lowest (0.165%) to 0.97 mm for the highest (2.64%) concentration. The progression of the inhibitory effect of pendimethalin occurred with every following assessment. The highest inhibitory effect determined was 12 DAI, when the width of the inhibiton zone at a concentration of 0.165% was 0.61 mm. The width of the inhibition zone significantly increased with increasing the pendimethalin concentrations and at a concentration of 2.64% it was 2.46 mm. The results of this study indicate the negative effect of herbicide pendimethalin on bacteria B. japonicum, even at concentrations lower than recommended concentrations that are applied in the field.