Impacts of nitrogen fertilisation amount and timing on grapevine nitrogen and carbon status in high yielding vineyards of south of France

Abstract

Maintaining grapevine productivity with limited inputs is crucial in Mediterranean areas. Apart from water, nitrogen supply is a major limiting factor for grapevine growth and metabolism. The present study focused on the nitrogen nutrition of a fertirrigated Sauvignon Blanc vineyard in the Mediterranean region, producing high yields (15 t/ha) and benefiting from a reduced post-harvesting period. The impact of nitrogen fertilization amount (0U, 40U and 120U) and timing (8-10 open leaves, mid-bloom, mid-veraison) on grapevine growth, yield components, nitrogen- and carbon- metabolisms were analyzed over 3 consecutive years and compared to a non-irrigated and unfertilized control. Leaf nitrogen status was moderate to high for all treatments, indicating an important buffering effect of the soil. Higher or earlier nitrogen supply slightly increased the number of bunches and final yield for the most fruitful vintages only. However, bunches sizes and the percentage of biomass allocations toward the above-ground organs were not impacted by the nitrogen treatments. In addition, the photosynthesis rate over the four years was similar among the treatments. A nitrogen nutrition indicator measured from hand-held sensors (SPAD, N-tester) at different periods of the cropping season was proved to be effective to simply compare the different fertilization strategies. This study highlighted the need for a better assessment of nitrogen requirements in fertirrigated vineyards of South of France to optimize plant functioning while avoiding environmental losses. Simple using-tools were shown to be relevant for that purpose.