Isotopic approaches to assess nitrate accumulation in conventional and organically grown vegetables

Excessive nitrate accumulation in vegetables poses a dual challenge to food safety and environmental sustainability. Substituting organic fertilizers for chemical fertilizers has emerged as an effective strategy to mitigate excessive nitrate levels in edible plant tissues, but the mechanistic understanding of organic nitrogenous transfer, and reliable authentication frameworks to assure organic produce still remains incomplete for some vegetables. Stable isotope techniques ( 15 N tracing, bulk isotopes δ 15 N, δ 13 C, δ 2 H, δ 18 O, and nitrate isotopes δ 15 N-NO 3 − , δ 18 O-NO 3 − ) offer unique advantages for tracing nitrogen sources, unraveling microbial and enzymatic processes, and capturing isotopic fractionation during nitrogen transformations. This review synthesizes current advances in applying isotopic approaches to clarify plant nitrate content under organic and chemical fertilizer usage, emphasizing altered nitrogen supply dynamics, microbial regulation, and carbon–nitrogen coupling. We also highlight how crop-specific isotopic fingerprints support the identification of organic and conventional cultivation practices across vegetable types (leafy, fruit, root/tuber, and leguminous plants), thus providing novel tools for organic production certification, food authenticity verification, and safety assessment. Future research priorities include integrating multi-isotope datasets with molecular microbial ecology and isotopomics to establish robust, mechanism-based traceability frameworks that link agricultural management practices with vegetable quality and safety.