Impact of Silver Nanoparticles (AgNPs) on Longidorus elongatus in Substrates Amended with a Soil-Enhancing Fertilizer Derived from Sewage Sludge in a Pot Experiment with Cucumis sativus L

This study investigated the impact of matrixless silver nanoparticles (AgNPs) stabilized with Ag cations on Longidorus elongatus in substrates amended with a soil-enhancing fertilizer derived from sewage sludge, using a pot experiment with cucumber ( Cucumis sativus L.) as the test plant. Seedling substrates were prepared by mixing granulated sewage sludge (A1, A2) with peat (P) at 25%, 50%, and 75% (mass fraction), while AgNPs were applied at a dose of 23.8 mL per pot. Plant performance was evaluated using biometric and physiological parameters, whereas nematode communities were extracted using the Baermann method and classified into trophic groups. The results demonstrated that substrate amendments significantly modified soil chemical properties, nematode abundance, and plant growth responses. AgNP exposure led to a substantial reduction in L. elongatus abundance, from 38–42 to 3–5 individuals per 100 cm 3 relative to control substrates. The strongest reduction was observed under conditions of increased silver availability, indicating its significant role in limiting nematode population development. Overall, the combined application of sewage sludge-based fertilizers and AgNPs substantially influenced soil–plant–nematode interactions. These findings indicate that AgNPs may serve as an effective tool for regulating plant-parasitic nematodes within organically amended substrates, while simultaneously influencing plant growth and soil chemical dynamics.