ESTIMATION OF THE ANNUAL COST OF KIWIFRUIT VINE GROWTH AND MAINTENANCE

Elemental analysis (for carbon, hydrogen, nitrogen and sulphur) and as h data for kiwifruit [Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward] stems, leaves and fine roots were used to calculate the specific costs (kg carbohydrate kg(-1) dry matter) of organ synthesis with ammoniacal nitrogen supply. Those cost s ranged between 1.19 and 1.35 for stems and 1.19 and 1.27 for leaves. The mean annual specific cost for fine roots was 1.17. Seasonal vine growth costs were calculated by multiplying the specific costs by biom ass data for a typical vine. Total cost of synthesis was 57.2 kg carbo hydrate per vine year(-1), taking fine root turnover as three times pe r season. Nitrate nitrogen supply increased that cost by 6.6 % to 61.0 kg carbohydrate per vine year(-1). Fruit growth accounted for the lar gest proportion of synthetic costs. Vine growth respiration (expressed in terms of carbohydrate equivalents) accounted for approximately 11. 5 % of the total cost of synthesis. Maintenance respiration was estima ted to be 5.28, 8.44, 1.90, 8.62 and 13.3 kg carbohydrate per organ ye ar(-1) for stems, leaves, fruit, above-ground perennial components and roots, respectively. Total annual cost of growth and maintenance for a mature vine was 94.7 and 98.5 kg carbohydrate per vine year-l with a mmoniacal and nitrate nitrogen supply, respectively. Both values are s imilar to an estimate of vine photosynthesis. Maintenance respiration accounted for approximately 40 % of the total annual cost of vine grow th, regardless of the form of nitrogen supplied. Peak carbohydrate dem and was during the period from 60 to 160 d after budbreak. (C) 1995 An nals of Botany Company