Summary
This long-term field study by Mitchell et al., published in the Journal of Agricultural and Food Chemistry (2007), compared flavonoid concentrations in tomatoes grown under certified organic and conventional management systems over a decade at a research site in California. The findings indicate that organically managed tomatoes contained substantially higher levels of quercetin and kaempferol glycosides than their conventionally grown counterparts, with the divergence becoming more pronounced over time, suggesting a cumulative soil and management effect. The authors attribute the differences principally to reduced soluble nitrogen availability under organic regimes, which is known to stimulate secondary metabolite biosynthesis in plants.
UK applicability
The study was conducted in California under specific climate and soil conditions not directly replicable in the UK; however, its findings on the relationship between nitrogen management, organic certification, and flavonoid accumulation are broadly relevant to UK horticultural systems and inform ongoing debates around organic produce quality within UK and EU policy contexts.
Key measures
Flavonoid concentration (quercetin and kaempferol glycosides, mg/kg fresh weight); crop management system (organic vs conventional); year-on-year trends over ten growing seasons
Outcomes reported
The study measured the concentration of flavonoids, specifically quercetin and kaempferol glycosides, in tomatoes grown under organic and conventional management over a ten-year period. It reported significantly higher flavonoid levels in organically managed tomatoes, likely attributable to differences in nitrogen fertilisation and soil management practices.
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