Biochemical characteristics of cover crop litter affect the soil food web, organic matter decomposition, and regulation of plant-parasitic nematodes in a banana field soil
Suppression of plant-parasitic nematodes and decomposition of organic matter are important soil food web functions. The availability and nature of carbon substrates in soil drive the structure, dynamics, and activities of soil food webs and may alter the way they function in the ecosystem. In this study, we assessed the effects on nematode communities of incorporating litter from three cover crops with contrasting biochemical characteristics into soil taken from a banana field. The litter type influenced nematode taxa and functional guilds during the 90-day assay. The cellulose- and hemicellulose-rich litters of Crotalaria zanzibarica and Paspalum notatum induced similar nematode successions, causing bacterivorous and fungivorous nematode populations to increase early in the study period and promoting a fungal decomposition pathway at the end of the trial. These two litters were the most effective at decreasing the soil's nematode infective potential with regard to major banana plant-parasitic nematodes, such as Pratylenchus coffeae, Helicotylenchus multicinctus, and Rotylenchulus reniformis. C. zanzibarica showed good potential as a green manure plant, as it increased the soil mineral nitrogen content during the 45 days following incorporation of litter. By contrast, litter from Acacia auriculiformis, which had high lignin content, induced immobilization of soil nitrogen and did not significantly increase microbivorous nematodes before day 45. This treatment failed to reduce the soil's nematode infective potential for H. multicinctus and R. reniformis populations. Our study also showed that the dynamics of nitrogen mineralisation in soil were related to the C:N ratio of litters but not to the decomposition pathway. The biochemical characteristics of litters appear to be critical drivers of nematode ecological successions and decomposition pathways following plant litter amendments to soil taken from a banana field.