Response of Leucadendron ‘Safari Sunset’ to regulated deficit irrigation: Effects of stress timing on growth and yield quality

Abstract

Leucadendron ‘Safari Sunset’ is the most important cultivar in the worldwide Protea industry. The commercial product consists of long branches that terminate in a female inflorescence (“head”), surrounded by large, deep-wine-red leaves. The dimensions of the colourful head have a predominant effect on the attractiveness and price of ‘Safari Sunset’ in the floricultural markets. The objective of the present study was to assess the effect of regulated deficit irrigation at different growth phases, on plant growth and crop quality. The experiment included two control treatments applied throughout the growth season: non-stress irrigation and deficit irrigation (40% of non-stress irrigation). The intermittent deficit irrigation treatments included periodic water stress during the fast vegetative growth (phase I) or during the head development (phase II). In addition, short events of water stress in the middle of the growth season, followed by a water non-stress irrigation regime were tested. Water stress throughout the growth season induced significantly low vegetative growth and small heads. Intermittent water stress (both periods) impaired crop quality, mainly because of reduction of head dimensions. Short or moderate periodic water stress barely affected head dimensions or the number of marketable branches, but impaired the product by diminishing the leaf dimensions. Continuous measurements of soil-water tension or plant indicators such as stem diameter or length were found to be very useful for on-line control of plant-water status.