Crop yield response to water - Cra

Shiraz, Grenache and Mourvèdre in southern FranceFigure 5 outlines a scheme for water management derived for Shiraz, Grenache and Mourvèdrein vineyards of southern France (43 o N) with contrasting soil types (Pellegrino et al., 2006). Thisscheme is based on eight classes of water deficit and aims at quality wine production. It highlightsthe need for good water supply, i.e. fraction of transpirable soil water (FTSW) above 0.6, earlyin the season. This allows for the establishment of a balanced canopy and fruit load, and properdevelopment of inflorescence buds that would largely determine next season's yield. A mildwater deficit from flowering to veraison, (FTSW between 0.6 and 0.4) leads to a drier finish toaccount for disease and berry composition at harvest. High water supply, particularly duringripening, may lead to a combination of undesirable indirect (e.g. disease) and direct effects onberry composition and wine quality. The goal of this RDI regime is to achieve a dry finish thatoften leads to higher concentration of colour and flavour compounds in berries.Cabernet Sauvignon in California, United StatesPrichard (2009) derived an RDI regime based on extensive experimentation with matureCabernet Sauvignon at Lodi (38 o N). The regime aims at the best yield/quality relationshipand is conceptually similar to the general pattern outlined above, namely ensure goodwater supply at the beginning of the growing season, and progressively reduce water supplytowards ripening. After harvest, full watering is recommended to encourage root growthand accumulation of plant reserves in an environment notably warmer and with greaterevaporative demand than in the previous case study.Pinot Noir and Tempranillo in Lleida, SpainGirona et al. (2006) used mid-day leaf water potential to schedule irrigation of 12-year-oldPinot Noir vines at Raïmat (42 o N) during three consecutive seasons. They used the samegeneral principle of ensuring water supply early in the season and allowing for a deficit at latereproductive stages using the thresholds summarized in Table 6. The RDI in this study reducedyield by 14-43 percent, increased irrigation water productivity by 28-46 percent and improvedconcentration of anthocyanins and polyphenols in berries by 10-19 percent (Table 6).Working with Tempranillo in the same environment, Girona et al. (2009) measured the effectof timing of water deficit on must attributes including soluble solids content, polyphenol,and anthocyanin concentration. They found negative impact of water deficit between fruitset and veraison and positive effects of mild water deficit after veraison. They proposed thatirrigation management should aim to avoid severe water deficits for Tempranillo beforeveraison and that RDI should target the window between veraison and harvest.Sauvignon Blanc in Marlborough, New ZealandIrrigation in this cool climate needs to account for the high evaporative demand in mid-summer(ET o > 7 mm/d) and the risk of excess irrigation with negative effects in terms of both wine qualityand environmental deterioration associated with leaching of nutrients and pesticides. Grevenet al. (2005) established an RDI study on 5 ha of 9-year old Sauvignon Blanc. They combinedmeasurements of vine water use, assessments of vegetative and berry growth, and modelling tocalculate transpiration. Before veraison, vines were irrigated when predawn leaf water potentialwas below –0.2 MPa and the threshold was –0.4 MPa between veraison and harvest. Preliminarygrapevine 481