Soil nematode community response to fertilisation in the root-associated and bulk soils of a rice-wheat agroecosystem

The practice of growing agricultural crops in rows results in larger soil nematode populations in the root-associated soil than in the bulk soil between the rows. Fertilisers applied to improve grain yield generally increase the abundance of nematode communities in agricultural soils. The objective of this study was to compare total nematode density and four dominant genera in the root-associated and bulk soils of paddy rice and upland wheat receiving organic and mineral fertilisers. Dominant nematode genera accounted for 80% of all nematodes and represented four trophic groups. There was greater total nematode density and a higher enrichment index (EI) but less nematode diversity (H') and a lower structure index (SI) in the root-associated soil than bulk soil of upland wheat. By contrast, nematode abundance, diversity and ecological indices were similar in the root-associated and bulk soils of the paddy rice. Soil nematode communities were affected significantly and consistently by fertilisation in upland wheat and paddy rice phases. More herbivore Hirschmanniella were present with mineral fertiliser than in the non-fertilised control. Straw-based organic fertilisers increased the abundance of bacterivore Eucephalobus. The lack of interaction between rhizosphere effect and fertilisation indicated that crop-growing conditions (different species and water regimes) were more influential on nematode communities and not consistently impacted by short-term organic and mineral fertilisation in the rice-wheat agroecosystem.