Influence of time of shading on flowering and yield of kiwifruit vines

Kiwifruit vines (cv. Hayward) were shaded with windbreak doth during two growing seasons, so that they received 45% of full sun for periods of 11 to 14 weeks. Shading vines prior to an thesis (flowering) did not affect the weight of individual fruits. Post-an thesis shading reduced fruit weights by an average of 11% when the shading was applied in midsummer (December to February), and by 5% when the shading was applied in late summer (March until May). However, the greatest effects of post-anthesis shading occurred in the following year, when the number of flowers per winter bud was reduced by 15% following mid-summer shading, and by 23% following late-summer shading. Although shading had a greater influence on return bloom than on fruit size, the higher prices paid to New Zealand growers for large kiwifruit resulted in fruit size having the major effect on financial returns. Shading vines during mid-summer, when fruit growth is rapid, is predicted to result in a cumulative loss in net return of 41%. This consists of 28% in the current year, and 13% in the following year, while for late-summer shading the predicted cumulative loss is 25% (13% + 12%).