Ethrel (2-chloroethylphosphonic acid) applied as a foliar spray to blueberry two weeks before first harvest resulted in a significant increase in the percentage of the total yield of ripe fruit harvested in the first picking. The increase in fruit ripe at first picking occurred at a concentration of Ethrel as low as 240 ppm on the Weymouth variety, but for the Blueray variety 1920 ppm were needed to produce the same effect. Ethrel-treated berries were smaller and were less acid than control berries.
Color enhancement in Howes and Early Black cranberry, as measured by pigment analysis and influenced by malathion, indole-3-acetic acid (IAA) and succinic acid 2,2-dimethyl hydrazide (Alar) sprays prior to harvest, was investigated under New Jersey conditions. Malathion at the rate of 2.5 lbs. of active material/A. applied at 200 gal./A. significantly enhanced the extractable pigment content in both Howes and Early Black cranberry. The color enhancement was noted within four days of application, and the differential in pigment content between the malathion treated and control berries was maintained throughout the sampling period. Neither IAA at 50 ppm nor Alar at 2000 and 4000 ppm active material increased color in Early Black. There was an indication that Alar delayed red pigment formation in Early Black. Soluble solids and titratable acidity measurements of Howes and Early Black fruit did not indicate any significant difference between treated and control fruit at a given sampling date.
The response of ‘Early Black’ cranberry (Vaccinium macrocarpon Ait.) to differential levels of N applied to new bogs on an Atsion sand in New Jersey was monitored over a 5-year period. More than 17 kg N/ha/year did not increase the earliness of bearing in a new bog nor did it increase the productivity of a bog. Greater amounts of N resulted in poorer berry color in early harvested fruit, increased fruit rot and vegetative growth. A strong biennial bearing tendency appeared to be related to new upright production. Differential N treatment did not influence this biennial bearing tendency. N analysis of plant tissue was not an effective diagnostic method of measuring fertilizer response, due in part to the effective dilution of plant N content by increased vegetative growth. N deficiency symptoms did not develop in the range of 0.74 to 0.82% N in the cranberry plant. Vegetative growth was particularly sensitive to N fertilization and warrants consideration as a diagnostic tool for evaluating N response.
Field applications of N greater than 34 kg/ha to highbush blueberry plants on an Atsion sand did not result in increased fruit production. Application of more than 64 kg N/ha may be detrimental to blueberry production. The optimum N content in the median leaves sampled one month after harvest of lateral shoots averaged 1.65% N over a 5 year period. A biennial bearing pattern occurred consistently at each of N fertilizer levels. Leaf N levels tended to be lower during years of high production than during years of low fruit production. Ca levels in leaf tissue were found to be below the sufficiency level during low production years when leaf N was high and above the sufficiency level in high production years when leaf N was lower.
The response of ‘Early Black’ cranberry (Vaccinium macrocarpon Ait.) to different water table depths maintained in new bogs on an Atsion sand in New Jersey was measured over a period of 5 years. A 30–38 cm water table resulted in significantly higher fruit yields in 4 out of 5 years when compared with plantings at a water table of 46–54 cm and in 3 out of 5 years when compared to plantings maintained with a water table at 38–46 cm. Average vine length was greatest in plantings at the 46–54 cm water table depth, and the number of fruiting uprights was greatest in plantings maintained at the 30–38 cm water table depth. Differences in water table depth did not influence fruit rot in plantings that received fungicide treatments, nor was color of fruit influenced by water table.
A field planting of ‘Bluecrop’, a mature highbush blueberry (Vaccinium corymbosum L.), on a Berryland soil type was subjected to differential levels of K fertilization over a 6-year period. Fruit yield and berry size were related to fertilizer treatment, leaf composition, and available soil K analysis. Blueberry production was highest at a 40 kg K/ha rate of potassium sulfate fertilizer which resulted in a leaf K sufficiency range between 0.45% and 0.55% K. Available soil K was significantly correlated to fruit yield.
Ethrel at 600 ppm applied as a 200 gal/A preharvest spray to ‘Early Black’ cranberry increased anthocyanin development. Gardner Color Difference Meter readings of fresh fruit indicated that Alar-treated fruit had higher reflectance than control fruits suggesting a delay in surface coloring. Ethrel, Alar, and malathion preharvest sprays did not influence yield or size of the fruit.
In 3 consecutive years of treatment, ethephon applied at the rate of 1 lb./A of active material and malathion at 21/2 lb./A of active material, 2 weeks before harvest, increased anthocyanin content in ‘Early Black’ cranberries, but SADH at 4 and 8 lb./A did not. None of the materials adversely affected yield or berry size during the 3 years of testing.
Increasing rates of N fertilizer from 16 to 64 lbs. of N/acre were associated with increased vine growth, and increased upright length in ‘Early Black’ cranberry. N content of stem tissue averaged 0.40%, runner leaves ranged from 0.92 to 1.09% N, fruiting uprights from 0.84 to 1.04% N, and non-fruiting uprights from 0.89 to 1.10% N. Leaf and upright N composition were highly correlated to N rate but stem N content did not correlate with N level. N content of runner leaves correlated best with vegetative growth. A significant quadratic component of the regression of N content of runner leaves upon upright length and of N content of fruiting uprights on runner production suggested that excessive vegetative growth may have influenced N composition in these tissues through a dilution mechanism.
Mother block plantings of 6 cultivars of highbush blueberry (Vaccinium corymbosum L.) for the production of cutting wood were successfully grown at 30.5 × 30.5 cm spacings on a Berryland soil. At this spacing 4- and 5-year-old ‘Bluecrop’ plants produced at the rate of 5.27 million cuttings per ha. Cutting wood production increased with increasing N fertilization. Optimum rate of N application was in excess of 45 kg N/ha. Application of fungicide under certain conditions increased weight per cutting.