SEASONAL PATTERNS OF LEAF MINERAL CONTENT OF KIWIBERRY CULTIVARS

Although the kiwiberry (Actinidia argute) is a recently introduced commercial crop in Belgium, it already covers over 30 ha and this area is increasing steadily every year. With the canes growing up to 4 m per year, kiwiberry plants are considered as fast growing. As the vines are so vigorous, growth control is a considerable challenge for the growers and an adequate fertilizer management is necessary to obtain healthy kiwifruit vines, an optimum productivity, and an optimal fruit size. Because information on this matter is scarce, in this study we set out to gain more insight into the fertilization and nutrient needs of the kiwiberry plant. As a first step to optimize the fertilization, the mineral leaf composition of five A. argute cultivars, ‘Issai’, ‘Weiki’, ‘Geneva’, ‘Kiwino’ and ‘Ambrosia grande’ was monitored during the growing season of 2012. We determined the content of nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, boron, copper, zinc, iron, manganese, and sodium in adult leaves of mature, fruit bearing plants without deficiency symptoms sampled at 5 time points. A clear seasonal pattern for most of the nutrients was uncovered. Whereas, the potassium content decreased throughout the growing season, for nitrogen, phosphorus, copper and zinc, after an initial decline, a constant level or even a slight increase was measured. The calcium, magnesium and boron content showed an increasing trend during the growing season. Finally, for the remaining nutrients, no or a cultivar-dependent trend was observed.