Yield and Quality Response of ‘Concord’ Grapes to Training Systems and Pruning Severity in Arkansas

Abstract

of pruning mechanization (3, 7), which requires cordon trained vines, there is a need to shift to cordon training systems.GDC training will increase vine productivity and aid in maintaining acceptable fruit quality compared to SC training in Arkansas (1).However, the comparison of 'Concord' trained to GDC, SC, and UK under Arkansas conditions has not been made.Preliminary studies in Arkansas indicated that the conven tional pruning schedule of 30+10 (30 nodes retained for the first 454 g (1 lb.) of 1 year old prunings and 10 additional nodes retained for each additional 454 g of prunings removed) may be too severe to obtain maximum fruit yields with ac ceptable juice quality from GDC trained vines (1).The objec tive of this study was to evaluate the response of 'Concord' yield and juice quality to GDC, SC, and UK training systems under 2 pruning severities. Materials and MethodsThis study was conducted for 5 years (1974)(1975)(1976)(1977)(1978) in an own-rooted 'Concord' vineyard established in 1957 at the Arkansas Agricultural Experiment Station, Fayetteville, on a Lintonia silt loam.The GDC trellis was converted from a SC trellis by installing 2 horizontal wires with a 1.2 m spread as described by Shaulis et al. ( 9) and extending each cordon to 2.4 m in length during the fall of 1973.The SC trellis had two 1.2 m cordons.UK was established as described by Shaulis et al.(5).The trellis height of each system was 1.8 m.Vine size in 1973 averaged 1.3 kg/vine.All vines were balanced pruned to either a 30+10 or 70+10 schedule (30 or 70 nodes retained for the first 454 g of 1 year old dormant prunings and 10 additional nodes retained for each additional 454 g of prunings removed).Fruiting nodes on GDC and SC trained vines were retained on 6-node canes and canes on UK trained vines were 12-15 nodes long.All vines on GDC and SC systems were shoot positioned (current season's growth positioned vertically toward the vineyard floor) and shoots on UK trained vines were allowed to grow at random.Records were kept for individual vine yields and pruning weight.Each treatment was imposed on the same vines each year.The experimental design was a 2 x 3 factorial with 7 replications of 4-vine plots.Samples consisting of 3 whole basal clusters were collected at harvest from each plot and immediately frozen in polyethyl ene bags for later analysis.All treatments were harvested in 1974 and 1975 when a composite sample of 100 randomly sampled berries on vines trained to the UK system pruned to the 30+10 severity tested 15% soluble solids and in 1976-1978 when this treatment tested 16%.Harvesting was on Aug. 22, Aug. 21, Sept. 3, Sept. 7, and Sept. 12, for 1974-1978, respectively.For quality analysis, berries were separated from stems, counted, and weighed to determine individual berry weight and number of berries/cluster.The number of completely green berries in each cluster were determined.The samples (green and colored fruit recombined) were then blended for 15 sec in a laboratory blender, placed in 250 ml beakers, warmed to 20°C, and % soluble solids were determined using a Bausch and Lomb Abbe refractometer.For color and acid determinations, beakers containing the blended samples were covered with watch glasses and placed in a water bath at 85°C for 1 hr, removed and cooled to about 40°.Pulp was removed by straining samples through 2 layers of coarse cheesecloth.A 5 ml aliquot of juice was diluted to 100 ml using distilled water, centrifuged, and optical density was read on the centrifuged samples using a Bausch and Lomb spectrophotometer (model 340) at 520 nm.Another 5 ml aliquot of juice was diluted to 125 ml using distilled water, and titrated to pH 8.4 with 0.1 n NaOH.Acidity is reported as % tartaric acid.