How climate and pest hazards, crop protection, cover cropping, and fertilisation explain yield gaps in vineyards of southern France

In vineyards, annual farming practices are essential for fully understanding all factors influencing grapevine yield gaps. However, the comprehensive impact of these decisions on grapevine yield at a large scale remains relatively unexplored. Gaining a deeper understanding of how these factors influence yield could serve as a key strategy for mitigating yield losses, particularly those exacerbated by climate change, thereby supporting sustainable wine production. In this study, we used random plot data from surveys conducted among winegrowers in the Languedoc-Roussillon wine region over four different years (n = 3,507). Our analysis aimed to explore the relationships between grapevine yield gaps and: 1) environmental and pest hazards; 2) plant protection management practices; 3) soil surface management practices; and 4) fertilisation practices. We employed a combination of graphical observations and statistical tests to assess the influence of these factors on grapevine yield. Our findings revealed that 58 % of the winegrowers did not achieve their target yields, with important yield gaps of around 32 % yield reduction on average. Plots suffering from climatic and pest hazards during the surveyed year showed important yield gaps across various management options. Considering grapevine protection, only very low levels of TFI (Treatment Frequency Index) resulted in yield gaps of around 10-20 % reduction, but no yield differences were found for other TFI levels. As high TFI was not necessarily associated with high pest pressure in the observed dataset, a substantial margin for pesticide reduction remains possible without yield losses. Cover crop management did not show significant yield gaps. Lower yields, by 10 %, were observed in non-fertilised PGI (Protected Geographical Indication) plots. However, no yield differences in relation to fertilisation were found in PDO (Protected Designation of Origin) wine plots, probably due to a lower level of nutrient extraction. Our results evidenced that when key annual farming practices were implemented, they could be involved in significant yield gaps, with around 10-20 % yield losses. Overall, our study highlights the importance of conducting large-scale and real-world data analysis at the regional level to evaluate grapevine yield gaps.