Effect of microbiological preparations and mineral amendments on root-knot nematode (Meloidogyne hapla) populations in greenhouse carrot production in Croatia

Abstract: Root-knot nematodes (Meloidogyne spp.) are a major constraint in carrot production, reducing yield and quality. This study assesses the impact of soil amendments on controlling Meloidogyne spp. populations in carrots under greenhouse conditions in Croatia where chemical nematicides are restricted. The efficacy of five soil treatments was evaluated: Control, EM Aktiv (EM), Fermented Plant Extracts (FPE), EM + Biolit (B), and EM + TerraFert Boden (TB) on Meloidogyne hapla populations and carrot (hybrid Napoli) growth under greenhouse conditions in Vardarac, Croatia, from December 2013 to May 2014. Treatments were applied 10 days before sowing in a randomized block design with four replicates per treatment. Nematode populations were monitored, and plant and root biomass, as well as root galling index, were assessed at harvest. The lowest root galling index was recorded in the EM + B (0.63) and FPE (0.65) treatments, significantly reducing M. hapla populations compared to the control. The EM treatment alone led to the highest nematode population (121.25 per 100 ml soil), while EM + TB, despite a slightly higher galling index (0.85), resulted in the highest plant (139.72 g) and root biomass (127.48 g). These findings suggest combining EM with mineral or organic amendments enhances nematode suppression and plant performance more effectively than EM alone. This study demonstrates the potential of biologically based soil amendments to manage root-knot nematodes in sustainable carrot production systems. Through a combination of crop rotation and biological treatments, including the introduction of non-host crops and biocontrol agents, this research aims to provide sustainable alternatives for nematode management.