Short-Time Impact of Soil Amendments with Medicago Plant Materials on Soil Nematofauna

Soil amendments with plant materials from Medicago species are widely acknowledged for a suppressive effect on plant-parasitic nematodes but their impact on beneficial components of soil nematofauna is still unknown. A study on potted tomato was carried out to investigate the short-time effects on the overall nematofauna of dry biomasses from six different Medicago species, i.e., M. sativa, M. heyniana, M. hybrida, M. lupulina, M. murex and M. truncatula, incorporated to natural soil at 10, 20, or 40 g kg−1 soil rates. All amendments resulted in a significant decrease of the total nematofauna biomass, whereas total abundance was significantly reduced only by M. heyniana, M. hybrida, and M. lupulina biomasses. Almost all the Medicago amendments significantly reduced the relative abundance of plant-parasites and root fungal feeders. All amendments significantly increased the abundance of bacterivores, whereas fungivores significantly increased only in soil amended with M. heyniana, M. lupulina and M. sativa plant materials. Mesorhabditis and Rhabditis were the most abundant genera of bacterivores, whereas Aphelenchoides and Aphelenchus prevailed among the fungivores. Predators were poorly influenced by all the tested Medicago biomasses, whereas the abundance of omnivores was negatively affected by M. heyniana and M. lupulina. Values of the Maturity Index and Sum Maturity Index were reduced by treatments with M. heyniana, M. hybrida, M. lupulina and M. sativa plant materials, whereas most of the tested amendments decreased values of the Channel Index while increasing those of the Enrichment Index. Enrichment and bacterivore footprints raised following soil addition with Medicago biomasses, whereas composite and fungivore footprints were significantly reduced. According to their overall positive effects on soil nematofauna, amendments with Medicago plant materials or their formulated derivatives could represent an additional tool for a sustainable management of plant-parasitic nematodes.