Nitrogen Application Rate and the Change in Carbohydrate Concentration in Leaves, Fruit, and Canes of Gold Kiwifruit

ABSTRACT

Gold kiwifruit (Actinidia chinensis Planch. var. chinensis ‘Hort16A’) is an important crop for New Zealand. In this trial, all nutrients, except nitrogen (N), were applied at levels comparable to commercial practice. The control treatment received approximately 145 kg N/ha/y, a conservative rate of N application for kiwifruit. The zero-N treatment vines received all nutrients except N, and the high-N treatment received double the control levels of N. Carbohydrate concentrations in the leaves, fruit and canes of zero-N and high-N vines were determined periodically through the season for two years. There were lower total sugar concentrations in the leaves of the zero-N vines however total carbohydrate concentration content was higher in the zero-N fruit. Vegetative vigor was reduced in the zero-N vines when compared to the high-N vines. By reducing N, the partitioning of carbon to fruit appears favored. This effect may be due to modified sink strength under reduced N.

Keywords:

• fruit sugars
• source-sink competition
• Actinidia chinensis (Planch. var. chinensis ‘Hort16A’)

ACKNOWLEDGMENTS

Funding for this study was provided by Ballance Agrinutrients NZ Ltd. and the Sustainable Farming Fund, Ministry of Agriculture and Forestry, New Zealand.