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.
Agricultural water requirements for commercial production of cranberries1
Abstract: The commercial production of cranberries relies on abundant water resources for frost protection, soil moisture management, and harvest and winter flooding. Given water resource demands and regulations in southeastern Massachusetts, we sought to quantify the annual water requirement for the commercial production of cranberries. Based on 2 yr of monitoring across five sites, the mean water requirement for cranberries was 2.2 (±0.6) m yr-1 (one standard deviation in parentheses). On average, the 3 mo maximum area threshold of 3.15 ha was within ∼20% of the value currently used to establish water permits for renovated cranberry farms in Massachusetts. Variation in the water requirement was primarily related to differences in the harvest and winter floods, which combined for two-thirds of the annual water requirement. The water requirement for the winter flood exhibited the greatest annual variation (54%), which was relatively low for the harvest flood (20%). Environmental variation was significantly related to water requirements for the winter flood, as well as seasonal irrigation, and should be carefully considered in agricultural water use regulations.
COMBINING ABILITY FOR CANOPY GROWTH AND GAS EXCHANGE OF INTERSPECIFIC BLUEBERRIES UNDER MODERATE WATER DEFICIT
Progenies and clones of interspecific hybrid blueberries were evaluated for annual fraction of canopy volume (FCYV) and for difference in fraction of canopy volume between control and stressed plants (FCYV(C) - FCYV(S)) in a moderate water-deficit environment. The FCYV(C) - FCYV(S) data were used to determine combining ability effects. In addition, physiological processes of attached leaves of the clones were monitored with a portable photosynthesis apparatus. Specific combining ability (SCA) effects were significant for FCYV(C) - FCYV(S). The clone with the lowest mean for FCYV(C) - FCYV(S) was US75, a hybrid of Vaccinium darrowi Camp x V. corymbosum L. Clone JU64 (V. myrsinites Lamark x V. angustifolium Aiton) also had a low FCYV(C) - FCYV(S) mean, and its two progenies (JU64 x JU11 and G362 x JU64) had low progeny means. Stomatal conductance was lowered when blueberries were exposed to atmospheric and/or soil moisture stress that resulted in lower transpiration and photo- synthesis and increased or equal water-use efficiencies (WUE). Blueberry plants adjusted to moisture stress as the season progressed by lowering stomatal conductance and increasing WUE. In particular, stressed plants of US75 and JU64 had equal or higher WUE values than control plants. US226 was the most drought-susceptible clone in the study, and its stomata did not appear to be as responsive to moisture stress as the other clones. Breeding for higher WUE in a dry environment appears possible with the germplasm used in this study. Increased drought resistance is an important trait for future highbush blueberry cultivars. In much of the United States, water is a limited resource and must be rationed in years of extreme drought. A more drought-resistant blueberry would be adapted to new areas for production and would allow growers to produce a crop in dry years when irrigation is halted or lim- ited. Genetic variability for drought resistance is present in Vac- cinium spp. Some southern species grow in nutrient-impo verished sands subjected to frequent drought (Davies and Albrigo, 1984; Galletta, 1975; Lyrene and Sherman, 1980). In previous studies (Erb et al., 1988a, 1988b), a drought screening test was devel- oped. Accessions of some southern species (V. darrowi Camp, V, elliotti Chapman, and V. ashei Reade) were more drought- resistant than northern accessions (V. corymbosum, V. vacillans Torrey, and V. myrtilloides Michaux) (Erb et al., 1988b). In addition, clones deriving half their genes from a southern spe- cies were usually drought-resistant (Erb et al., 1988b). Davies and Albrigo (1984) suggested the above-mentioned southern species plus V. tenellum Aiton, V. myrsinites, and V. simulatum Small, and the northern species V. angustifolium and V. palli- dum Aiton as good sources of drought resistance. The water relations of V. ashei cultivars were first investi- gated in the late 1970s. Andersen et al. (1979) observed that irrigation reduced leaf diffusive resistance by 50% and increased transpiration by 70% over nonirrigated bushes of 'Tifblue',