The Interplay of Nitrogen and Boron in Rapeseed ( <i>Brassica napus</i> L.): Implications for Nutrient Uptake, Photosynthesis, and Rhizosphere Ecology

Rapeseed is highly sensitive to boron (B) and nitrogen (N) deficiency, yet their interaction effects on rapeseed remain poorly understood. Here, a factorial pot experiment revealed that under N-sufficient conditions, B deficiency severely impaired reproductive growth, photosynthesis, and yield formation, while also reshaping rhizosphere bacterial communities. However, moderate N limitation alleviated these negative effects. <i>Massilia</i> and <i>Sphingomonas</i> were identified as core microbiota responsive to B availability under N-sufficient conditions, correlating positively with B uptake and photosynthetic N use efficiency (PNUE). Shifts in microbial composition were linked to soil pH and available B, whereas reduced PNUE under B deficiency resulted from disrupted N allocation within the photosynthetic apparatus. Balanced N and B supply improved nutrient uptake, microbial stability, and seed yield, underscoring the importance of integrated nutrient management in sustainable rapeseed production.