Cranberry growth and yield response to fertilizer and paclobutrazol

Abstract

In glasshouse studies with cranberry, paclobutrazol (PP333) ((2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol) applied twice as a foliar spray at 75, 150, 300, 600 or 1200 mg 1 −1 decreased shoot and root growth, and the shoot: root ratio. Paclobutrazol decreased shoot elongation within 3 weeks of application and increased the number of branches on primary shoots. Buds were formed within 7 weeks of treatment and some contained flowers. In a second experiment, flower-bud formation was greater when plants were treated with paclobutrazol at 1.25, 2.50 or 5.00 mg pot −1 as a soil drench and grown for a longer period. Plants grew more with high NPK than with low NPK but growth was diminished still by paclobutrazol. High NPK decreased floral induction. Paclobutrazol was still detected in the soil 50 weeks after application. In a cranberry field study, foliar sprays of paclobutrazol at 75 or 150 mg 1 −1 at full bloom and 2 weeks later decreased fruit set, fruit size and yield, but increassed bud set and flower-bud set on uprights. Shoot growth was decreased the following year but the number of flowers per upright was increased. Fruit set was the most important contributor to yield variation, followed by fruit size and flowers per upright. The effects of paclobutrazol upon adjusted yield components accounted for a substantial amount of yield variation. No effect of cultivar on yield was apparent as the higher proportion of adjusted number of uprights flowering in cultivar ‘McFarlin’ was offset by an increased adjusted number of flowers per upright in cultivar ‘Bergman’. Bud set and flower-bud set were greater in uprights that did not flower in the current season.