The aim of this study was to investigate the nematocidal effect of the preparations based on fluopyram (pesticide) and liquid chicken manure (natural amendment) on the population density of the root-knot nematodes, Meloidogyne spp. in carrot crops. The field experiment was set up in four treatments: control (C), fluopyram (FLU), fluopyram and liquid chicken manure (FLU+LCM) and liquid chicken manure (LCM) by a random block design in four replicates. Population density of Meloidogyne spp. juveniles varied between the treatments, and the number of Meloidogyne spp. was significantly decreased in all treatments with fluopyram (FLU and FLU+LCM). All amended treatments (FLU, FLU+LCM, LCM) decreased galling of the roots and had a positive effect on carrot yield. The population of Meloidogyne spp. juveniles increased with the plant growth, regardless of the treatments applied. Fluopyram negatively affected the biodiversity indicating greater disturbance for the nematode community structure in the soil. It can be concluded that fluopyram and liquid chicken manure have nematicidal potential, while liquid chicken manure maintained or enhanced nematode biodiversity.; Cilj ovoga istraživanja bio je ispitati nematocidni učinak pripravaka na bazi fluopirama (pesticid) i tekućega pilećeg stajnjaka (prirodni poboljšivač tla) na gustoću populacije ličinki nematoda korijenovih kvržica, Meloidogyne spp. Poljski pokus postavljen je u četiri tretmana: kontrola (C), fluopiram (FLU), fluopiram i tekući pileći stajnjak (FLU + LCM) te tekući pileći stajnjak (LCM) slučajnim blok-rasporedom u četiri ponavljanja. Gustoća populacije ličinki Meloidogyne spp. varirala je između tretmana, a broj ličinki Meloidogyne spp. značajno je smanjen u svim tretmanima s fluopiramom (FLU i FLU + LCM). Svi pripravci (FLU, FLU + LCM, LCM) utjecali su na smanjenje gukavosti korijena. Navedeni tretmani pozitivno su utjecali na prinos mrkve. Populacija ličinki Meloidogyne spp. porasla je razvojem biljaka, bez obzira na primijenjeni tretman. Fluopiram je negativno utjecao na bioraznolikost, koja ukazuje na veća uznemirenja u strukturi zajednice nematoda u tlu. Može se zaključiti kako pripravci na bazi fluopirama i tekućega pilećeg stajnjaka imaju nematocidni potencijal, a tekući pileći stajnjak održava ili povećava bioraznolikost nematoda.