SummaryKiwifruit vines (cv. Hayward) were shaded so that they received 100%, 70%, or 45% of full sun (FS) from spring 1984 until spring 1987. Shading delayed bud burst by 3-5 d and flowering by 2-4 d. The effects of shading on flower production varied from year to year as the number of fruit on shaded and unshaded vines varied. Shaded vines consistently had fewer winter buds and fewer flowers per cane. In addition, the percentage of shoots bearing flowers, and the number of flowers per flowering shoot tended to be lower on shaded vines. After three seasons of shading, the reduction in flowering on shaded vines resulted in a large decrease (29% at 70% FS, 42% at 45% FS) in the number of fruit per vine. At these reduced crop loads, the average weight of individual fruit was not significantly affected by the shading. Shading resulted in small decreases in soluble solids concentration at harvest and small increases in the rate of fruit softening during storage at 0°C, but these differences are unlikely to be commercially significant on their own. The relationship between the number of fruit per vine (FN), the %FS, and the average fruit weight (FW) was described by the following equation:FW (g) = 105 - 0.035 x FN + 0.00022 x FN x %FS r2 = 0.63The frequency distribution of weights of individual fruit on a vine was normal, with a constant standard deviation of 14 g. Using this information, vine yield in terms of trays per vine was modelled to predict optimum numbers of fruit per vine under various levels of shading.
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Snelgar et al. (1991) studied this question.