Nematode soil food webs in maize agro-ecosystems and their implication on plant-parasitic nematodes

Abstract

Maize is the most important staple food crop consumed in Kenya and Africa. Plant-parasitic nematodes are a major constraint in maize production. On the other hand, free-living nematodes provide key ecological functions such as nutrient mineralization and pest suppression. The aim of this study was to assess the soil food web structure in maize agroecosystems in Kirinyaga County, Kenya in order to understand the potential role of predatory nematodes in suppresion of plant-parastic nematodes. Soil samples were collected from maize fields in Gichugu, Kirinyaga Central, Ndia and Mwea sub-counties in Kirinyaga County. Fifty nematode genera were identified across the sub-counties with Pratylenchus, Cephalobus, Heterocephalobus, Aphelenchus, Labronema and Nygolaimus being the most predominant genera in their respective feeding guilds. The highest enrichment index was recorded in Gichugu sub-county. Nematode functional metabolic footprints based on enrichment index and structure index characterized Mwea as a degraded ecosystem, while Gichugu, Kirinyaga Central and Ndia were structured. The plant-parasitic index was highest in Mwea sub-county although the differences between sub-counties were not statistically significant. Sub-counties which were characterized as structured had a low plant-parasitic index. Canonical correspondence analysis revealed a significant correlation between some soil physical properties, nematode indices and metabolic footprints. The results provide valuable information on soil food web structure and function in maize agro-ecosystems in Kirinyaga County, Kenya and they highlight the potential role of organic amendments in suppression of plant-parasitic nematodes in maize.