Light-induced soil legacy alleviates continuous cropping adversity on Nicotiana benthamiana growth

Aims Continuous cropping under artificial light is increasingly common in controlled-environment agriculture (CEA), yet it faces challenges like light stress and continuous cropping obstacles (CCO). This study explores how different light intensities shape the interactions among rhizosphere microbiota, soil properties, and allelochemicals during continuous cropping in CEA, with a focus on their roles in causing or alleviating CCO in plant. Methods We used Nicotiana benthamiana as the model plant and investigated its physiological responses, rhizosphere microbial dynamics, soil properties, and allelochemical profiles under different light intensities across three continuous cropping seasons. Results Low light significantly inhibited plant growth, but continuous cropping alone had minimal impact. In contrast, moderate light resulted in pronounced CCO, with high levels of allelochemicals (notably 2,4-ditert-butyl phenol and dimethylbenzene) disturbing microbial balance by suppressing beneficial bacteria (e.g., Streptomyces, Massilia), reducing functions like fermentation and nitrogen fixation, and increasing harmful processes such as denitrification. This disruption inhibited plant growth and intensified CCO. Soil legacy tests showed that removing negative legacies (allelochemicals and harmful microbes) eliminated CCO, highlighting their key role. Light-driven shifts in the microbiome increased by the third season. High light reduced yield decline between the second and third seasons, supporting more beneficial microbes. Under high-light conditions, lower allelochemical levels promoted beneficial microbes (e.g., Pseudomonas, Flavobacterium), stimulating plant hormone production and mitigating CCO. Conclusions Light intensity influences continuous cropping obstacles by regulating rhizosphere microbial structure and allelochemicals. These findings provide references for sustainable CAE management.