Vineyard Landscape Position Influences Grape Nitrogen via Soil Nitrogen Supply: Insights from Ion Exchange Membrane Monitoring

Abstract Aims Understanding the impact of landscape on soil nitrogen (N) dynamics is essential for optimizing vineyard productivity and grape quality. Our study investigated the effect of site and slope position on soil N supply, grapevine N uptake, and berry quality in a Chardonnay vineyard. Methods Combining ion exchange membrane (IEM) technology with plant N tests, we monitored soil mineral N fluxes, nitrogen exposure (NE), and plant responses across two distinct sites (S1: rapid-draining sandy soil; S2: imperfectly drained silt loam) over a growing season. Results We observed distinct site-specific behaviors. S1 exhibited higher mineral N fluxes (up to 4.5 µg N·cm⁻ ²·day⁻ ¹) and NE dominated by nitrate, whereas S2 stored more total N and organic matter. For both sites, lower slope positions showed 33% higher biological N availability, and 19% greater growing season soil N supply compared to upper slopes, linked to higher organic matter. Conclusions Sequential IEM placement effectively tracked plant-available N, expressed as NE, correlating strongly with vine N status. Site and slope position significantly influence N uptake, yield, and berry quality of grapevines by altering N mineralization and soil mineral N dynamics. These results provide a tool for optimizing N fertilizer management strategies within landscapes.