ESTIMATION OF THE ANNUAL COST OF KIWIFRUIT VINE GROWTH AND MAINTENANCE

Elemental analysis (for carbon, hydrogen, nitrogen and sulphur) and ash 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 costs 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 biomass data for a typical vine. Total cost of synthesis was 57.2 kg carbohydrate per vine year(-1), taking fine root turnover as three times per season. Nitrate nitrogen supply increased that cost by 6.6 % to 61.0 kg carbohydrate per vine year(-1). Fruit growth accounted for the largest 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 estimated to be 5.28, 8.44, 1.90, 8.62 and 13.3 kg carbohydrate per organ year(-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 ammoniacal and nitrate nitrogen supply, respectively. Both values are similar to an estimate of vine photosynthesis. Maintenance respiration accounted for approximately 40 % of the total annual cost of vine growth, regardless of the form of nitrogen supplied. Peak carbohydrate demand was during the period from 60 to 160 d after budbreak. (C) 1995 Annals of Botany Company