Sustainability-Oriented Compost Application Methods in Viticulture: Impacts on Chlorophyll Content, Yield, and Sauvignon Blanc Grape Quality

Soil organic matter replenishment is essential for sustainable viticulture because it improves nutrient cycling, water retention, and vineyard resilience. This study evaluated the effects of different compost application methods on leaf chlorophyll content, grape yield, and grape quality of Vitis vinifera L. cv. Sauvignon Blanc grafted onto Kober 5BB rootstock under Central European conditions during 2020–2022, following compost application in fall 2019. Leaf chlorophyll content was monitored weekly using an atLeaf+ chlorophyll meter calibrated against spectrophotometrically determined chlorophyll concentrations. At harvest, grape yield, soluble solids, titratable acidity, pH, and yeast assimilable nitrogen (YAN) were determined. Deep compost application consistently produced the highest chlorophyll concentrations, increasing seasonal means by 10.4%, 24.7%, and 25.4% compared with the unfertilized control in 2020, 2021, and 2022, respectively. Yield responses also increased over time, with deep compost application improving grape yield by 53.8% in 2021 and 60.7% in 2022. Effects on grape quality were smaller and varied among years, although compost-treated vines generally exhibited higher titratable acidity and YAN. The calibration of atLeaf+ readings against spectrophotometrically determined chlorophyll concentrations in grapevine leaves showed high accuracy (R2 = 0.9542). These results indicate that deep compost application may enhance grapevine physiological status and productivity while supporting circular nutrient management and may contribute to improved vineyard resilience under variable climatic conditions.