Field practices for adapting Mediterranean viticulture to climate change

Abstract

Field practices for adapting Mediterranean viticulture to climate change Mediterranean viticulture is being affected by climate change, which threatens wine typicity and, therefore, the whole viticulture sustainability. The main factors expected to affect grapevine cultivation are water scarcity, warm air temperature and the increase in the air carbon dioxide concentration, and impact of these factors will be mainly the: i) advancing of grapevine phenology, thereby decoupling berry technological and phenolic composition and ii) increasing vine water requirements. This PhD Thesis aimed at evaluating the effects of different field practices to adapt Mediterranean grapevine cultivation to climate change. Three experiments were performed in Valencia (Spain) to assess the effects of 1) regulated deficit irrigation; 2) training systems architecture and; 3) canopy management. The main responses evaluated were vineyard water-use efficiency (WUE) and grape composition. Experiment 1 was undertaken for three seasons in a drip-irrigated, cv. Muscat of Alexandria/161-49C vineyard to define the most sustainable irrigation strategy for white winegrapes in eastern Spain. For this, four treatments were tested: (i) Control, irrigated at 100% of estimated crop evapotranspiration (ETc) for the entire season; (ii) sustained deficit irrigation (SDI), irrigated at 50% of Control; (iii) early deficit (ED), where pre-veraison irrigation was withheld, followed by 100% ETc; and (iv) late deficit (LD), irrigated as in the Control until veraison and thereafter at 25% ETc until harvest. Results showed that yield in ED and LD was reduced 25 and 15%, respectively, compared to that of the Control, while yield under SDI did not differ significantly from that of the Control and was similar to that of the ED and LD treatments. All the deficit irrigation treatments had some carry-over effects on vine performance due to a significant decrease in shoot fruitfulness and in cluster mass due to smaller berries. The ED treatment, however, led to a greater reduction in berry growth compared to that of LD. Full irrigation increased pruning mass and leaf area mainly due to larger secondary shoots, and delayed grape ripening as well. In conclusion, the SDI treatment resulted in the greatest WUE, ensuring the high yield potential of the cultivar, providing that a threshold value of the water stress integral of 35 MPa day during the periods from anthesis to veraison and from veraison to harvest was not surpassed. In addition, the SDI strategy favoured an improved grape composition, particularly in terms of grape sugar accumulation. Therefore, sustained deficit irrigation at 50% of ETc should be applied to cv. Muscat of Alexandria where water is scarce or expensive, paying close attention to possible carry-over effects if water withholding has to be continued for longer than three seasons. In experiment 2, the effects of sunlight interception through the vineyard row's orientations on WUE and grape composition were assessed. The trial was