Legumes and cereals substantially contribute to humankind nutrition worldwide. These crops are often grown together or in rotation to enhance cereal production thanks to the nitrogen (N) fixing properties of legumes. Pests like root feeding nematodes have a considerable impact on crop yield. Root feeders affecting legumes are also known to enhance the transfer of symbiotically fixed N to neighboring grasses. It is, however, unknown how this process affects legume-grass competition. It also remains unknown how interactions with other soil organisms like bacterivores impact N dynamics and plant competition.
To address this research gap, chickpea and oat were grown alone and together. Treatments consisted of root feeding and bacterial feeding nematodes alone and in combination. Plants were grown in controlled conditions for 16 weeks. Plant measurements accounting for productivity (dried biomass) and N fixation (nodulation, ethylene assay) were considered at harvest. Stable isotopes were utilized to assess the N transfer to oats. Mineral N content in soil was also considered.
Results/Conclusions
Nematode treatments significantly influenced plant biomass and shoot N content. The presence of root feeders enhanced N transfer to oat, but this did not translate to improved grass performance. Conversely, oat was more negatively affected by root feeders when grown together with chickpea. The combination nematode treatment accounted for the lowest biomass in all plants, thus indicating a synergistic negative soil feedback resulting from indirect trophic interactions in soil. These results point to a greater effect of indirect trophic interactions than previously thought.