FIELD RESPONSE TO CPPU APPLICATION IN KIWIFRUIT (ACTINIDIA DELICIOSA 'HAYWARD') ORCHARDS TREATED WITH HYDROGEN CYANAMIDE IN NORTHWEST SPAIN

In northwest Spain, insufficient chilling hours result in low budbreak and flowering, and consequently poor fruit production in orchards of Actinidia deliciosa 'Hayward'. Hydrogen cyanamide increases budbreak and flower production in this and other mild climate regions. Application of CPPU (N-[2-chloro-4-pyridyl]-N-phenylurea) after fruit set can also enhance fruit production by increasing fruit size. Field experiments were carried out to study the combined effects of hydrogen cyanamide and CPPU on fruit production in two kiwifruit orchards at Pontevedra (NW Spain). Application of hydrogen cyanamide significantly increased fruit production, especially in one of the orchards, by 3–4 t/ha relative to the control. This effect was greater when plants received both hydrogen cyanamide and CPPU, leading to yields of 7 t/ha more than in control plots that received no treatments, and, what is more important from a practical point of view, to higher mean fruit weights and marketable production.