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- Author or Editor: J.R. Davenport x
This research was undertaken to document the extent of biennial bearing in flowering uprights by American cranberry (Vaccinium macrocarpon Ait) cultivar and growing region. Seven cultivars were studied: three found in all states considered (Massachusetts, New Jersey, Wisconsin, Oregon), two common to Massachusetts and New Jersey, and two other commercially grown cultivars, one each from Wisconsin and Oregon. There were significant cultivar, region, and cultivar × region interaction effects for both percent return bloom (%RB) and percent return fruit (%RF). Percent RB ranged from 74% for `Ben Lear' in Wisconsin to 14% for `Howes' in New Jersey. `Ben Lear' differed the most in %RB among regions, from 74% in Wisconsin to 14% in Massachusetts. However, in some regions, especially in Wisconsin, many blossoms did not set viable fruit. There was no significant difference in %RB among cultivars grown in Massachusetts or Oregon; however, cultivars grown in these regions did differ in %RF.
The ability to monitor plant nutrient status of high value horticultural crops and to adjust seasonal nutrient supply via fertilizer application has economic and environmental benefits. Recent technological advances may enable growers and field consultants to conduct this type of monitoring nondestructively in the future. Using the perennial crop apple (Malus domestica) and the annual crop potato (Solanum tuberosum), a hand-held leaf reflectance meter was used to evaluate leaf nitrogen (N) status throughout the growing season. In potato, this meter showed good correlation with leaf blade N content. Both time of day and time of season influenced leaf meter measurement, but leaf position did not. In apple, three different leaf meters were compared: the leaf spectral reflectance meter and two leaf greenness meters. Correlation with both N rate and leaf N content were strongest for the leaf reflectance meter early in the season but nonsignificant late in the season, whereas the leaf greenness meters gave weak but significant correlations throughout the growing season. The tapering off of leaf reflectance values found with the hand-held meter is consistent with normalized difference vegetation index (NDVI) values calculated from satellite images from the same plots. Overall, the use of leaf spectral reflectance shows promise as a tool for nondestructive monitoring of plant leaf status and would enable multiple georeferenced measurements throughout a field for differential N management.
Biennial bearing of uprights has been documented for cranberry (Vaccinium macrocarpon Ait.). Percent return bloom (%RB) may vary from 14% to 74% depending on cultivar and growing region. Floral initiation for the following season in cranberry takes place during the same time period as flowering and fruit set for the current season. This research was undertaken to document the effect of fruiting or not fruiting in the previous year on %RB and %RF (return fruit) in two cultivars (Stevens and Ben Lear) and five growing regions (MA, NJ, WI, OR, WA). Previous year fruiting caused a reduction in %RB compared to non-fruiting in the previous year. The effect on %RF was even greater. For `Ben Lear', uprights that fruited in 1990 had 31%RB and 22%RF while those that did not fruit in 1990 had 67%RB and 54%RF. Both %RB and %RF in 1991 were about 49% lower for `Stevens' which fruited in 1990 than those that did not fruit in 1990. It is still not clear whether biennial bearing in cranberry uprights is a function of hormonal interaction and regulation or of resource limitation or both.
Fruit mass development in `Crowley', `Pilgrim', and `Stevens' cranberry (Vaccinium macrocarpon Ait.) was compared in five states for two seasons. Comparing all locations, `Stevens' and `Pilgrim' cranberries had similar growth curves with a faster growth rate than that of `Crowley'. Regional differences in fruit development were observed. Shorter growing seasons, especially in Wisconsin, were compensated for by more rapid growth rates. Conversely, low initial mass and slower growth rates were compensated for by the longer growing season in the Pacific Northwest. Solar radiation intensity accounted for little of the variability in fruit growth. Neither growing degree days nor numbers of days were good predictors of cranberry fruit fresh mass accumulation. Instead, numbers of moderate temperature days (between 16 and 30 °C) appeared to be key, accounting for greater than 80% of the variability in cranberry fresh biomass accumulation. The most rapid growth rates occurred when temperatures were in this range. High temperatures were limiting in New Jersey while low temperatures were limiting in Oregon and Washington. In one of two seasons, low temperatures were limiting in Wisconsin: accumulation of 0.5 g fresh mass took 11 d longer. Massachusetts had the fewest periods of temperature extremes in both seasons, resulting in the shortest number of days required to accumulate 0.5 g fresh mass.