Critical irrigation threshold and cranberry yield components
Yield components are useful for characterizing the impact of crop management parameters on cranberry yield and are known to be influenced by irrigation management. This study was conducted to evaluate the potential contribution of cranberry yield components to maximizing yield, and the influence of the soil water tension threshold used to initiate irrigation (SWTI) on those components. During the 2011 and 2012 growing seasons, tensiometers were installed at three production sites in Quebec to test SWTI values ranging from 5.5 to 10.0kPa. Sites were cropped to cranberries to evaluate the impact of these irrigation treatments on yield components. The four most important cranberry yield components related to final yields were, in order of importance, the number of marketable berries per quadrat (BM/Q), the number of uprights per quadrat (U/Q), the number of marketable berries per upright (BM/U), and the marketable fruit set (BM/F). Significant reductions in BM/Q, BM/U and BM/F were observed when SWTI varied from 8.5 to 10.0kPa while a reduction in U/Q was associated with a SWTI of 5.5kPa. A SWTI ranging from 7.0 to 8.0kPa significantly improved the principal yield components.
Effects of timing of water stress on yield and berry size.
Past irrigation research in Marlborough showed that reducing irrigation on grapes by up to 60% would not have any impact on yield, but that the timing of the irrigation might be important for maintenance of yields. A research trial was set up with Sauvignon blanc grapes planted in containers; periods of water stress were applied for three weeks at different times of the growing season. During the three years of the trial the post-flowering (PO-F) period was consistently most sensitive to water stress. At harvest time, the crop yields for the PO-F water-stressed vines were 55%, 72% and 90% of control yields for the three consecutive years, and the bunch weights were 59%, 84% and 95%. Berry weights for the PO-F water-stressed vines were 87%, 96% and 73% of the control values, although the second-year difference was not significant. In two years out of three, there was a trend for PO-F and pre-veraison (PR-V) water-stressed vines to have the lowest berry soluble solids contents ( degrees Brix), indicating a delay in maturity. We suggest that to use irrigation sustainably, it is safe to reduce water applications for most of the season, but that immediately after flowering, any water stress should be avoided. During the period leading up to veraison, some mild water stress can be applied.
Production, qualité des fruits et croissance de pêchers soumis à différents régimes d'alimentation hydrique
Des pechers adultes ont ete irrigues en goutte a goutte par deux methodes de conduite : evolution du potentiel hydrique du sol (tensiometrie), ou interpretration des microvariations du diametre de tiges (micromorphometrie), comparees a un regime tres rationne en eau. La conduite par micromorphometrie induit une exploitation plus poussee de l'eau des horizons profonds avec donc, un volume d'irrigation beaucoup plus faible que par le pilotage tensiometrique utilise dans cet essai. L'importante economie d'eau n'a pas provoque de difference sur le calibre des fruits, la production et la croissance generale des arbres. Mais le traitement sec a fortement reduit la production de fruits. L'irrigation basee sur le suivi micromorphometrique reduit la chute des fruits en prematurite et favorise le developpement des racines alors que les arbres irrigues par controle tensiometrique produisent des fruits contenant moins de sucres a la recolte et de moins bonne tenue en conservation.