LAUSR

Nematode population and diversity in a West African rain-fed rice cropland amended with biochar (B), biochar plus inorganic fertiliser (B + NPK), inorganic fertiliser (NPK) and control (CK) without amendments were investigated in a 3-year field study. Results demonstrated that significant differences exist between treatments and years of study for total nematode population and nematode trophic groups. Total nematode density, nematode trophic group (bacterivore and plant-parasitic) density were increased and dominant in B + NPK compared with CK after 3 years. Relative abundance of nematode genera according to trophic group across treatments showed Hirschmanniella (23%) as the dominant plant parasites in NPK, and Heterocephalobus (27%), Aphelenchoides (22%) and Eudorylaimus (9%) as dominant bacterivores, fungivores and omnivores-predators, respectively, in B + NPK. Trophic group indicators showed that the fungivore plus bacterivore to plant-parasitic ratio (73%) was significantly increased by B + NPK treatment in comparison to CK. Conversely, treatments exerted no significant effect on the fungivore to bacterivore ratio (F/B) throughout the period of study, which implies less disturbance and adverse impact of biochar on nematode communities. Apart from treatments and environmental factors, changes in nematode trophic groups were strongly related to soil chemical properties, such as soil pH, total nitrogen and available phosphorus, which shows their influence on soil nematode community. Our result shows the positive effect of integrated addition of biochar and inorganic fertiliser in balancing nematode diversity and building a resilient soil ecosystem in a low input rain-fed rice cropping system.