Nitrogen Isotope Ratio (δ15n): a Nearly Unexplored Indicator That Provides Useful Information in Viticulture

The study of the natural abundance of nitrogen-stable isotopes is an aspect of viticulture research that has received limited attention. While stable isotopes of carbon, oxygen and hydrogen have received significant attention, nitrogen isotope ratio (δ15N) remains a less studied yet potentially informative parameter. This paper explores the implications of δ15N measurements in grapevines, shedding light on its utility as an indicator for nitrogen sources, plant water status, and within-field variability. The study examines the influence of nitrogen sources, dose, and sampling organs on δ15N values, revealing distinct trends in petioles, berries, and seeds. Organic fertilisers led to higher δ15N values compared to inorganic sources, while increasing nitrogen doses exhibited a much weaker effect on δ15N. Moreover, δ15N values vary spatially within vineyards, associating with its topography and potential soil composition, soil management and water availability. Our results highlight the importance of considering δ15N in viticulture, suggesting its integration with δ13C for comprehensive insights into nitrogen cycling and soil management practices. The findings advocate for further research to harness the full potential of δ15N as a valuable tool in viticultural studies.