Soil biota suppress maize growth and influence root traits under continuous monoculture

Aims: This study investigated maize-soil biota interactions as well as the soil legacy effects of continuous monoculture (CM) on maize performance. Methods: We conducted a glasshouse experiment that compared the performance of maize inoculated with living or sterilized soil inocula collected from experimental field plots with cropping histories of 1 to 5 years of continuous maize monoculture, where the soil type is Nicollet clay loam with moderate fertility. We measured the biomass, yield, root traits and leaf nutrients of maize as well as eukaryotic soil organisms. Results: Inoculation with living soil dramatically reduced maize biomass and yield compared to inoculation with sterilized soil, showing CM to have strong negative soil biotic legacy effects on maize. Nonetheless, the strength of soil biotic effects on most maize variables were relatively stable over time under CM. The response of maize total biomass to living soil inoculation correlated positively with arbuscular mycorrhizal (AM) fungal abundance but negatively with soil fauna abundance, whereas it did not relate with the abundance of plant pathogenetic fungi or herbivorous nematodes. The roots showed acquisitive syndromes (high specific root length but low root diameter) in sterilized soil but conservative syndromes (opposite traits) in living soil. The responses in root system structure were tightly related with AM fungal diversity and community composition. Conclusions: Our study shows strong and stable negative effects of soil biota on maize under CM. The complex effects of soil biota on maize performance highlight the need to explore the functions of different groups of soil organisms to better understand and control negative soil legacy effects in agroecosystems.