RT Journal Article SR Electronic T1 Effects of Long-Term Nitrogen, Phosphorus, and Potassium Fertilization on Chenin blanc Vines. II. Leaf Analyses and Grape Composition JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 91 OP 98 DO 10.5344/ajev.1989.40.2.91 VO 40 IS 2 A1 W. J. Conradie A1 D. Saayman YR 1989 UL http://www.ajevonline.org/content/40/2/91.abstract AB The effect of N, P, and K fertilization on the nutrient concentrations in leaves and on grape and wine quality of Chenin blanc was followed over a period of 10 years. The levels of N were 16 (N0), 56 ( N1), and 96 (N2) kg/ ha/yr; P applications were 0 (P0), 9 (P1), and 18 (P2) kg/ha/yr; and K applications were 0 (K0), 45 (K1), and 90 (K2) kg/ha/yr. Nitrogen fertilization caused only marginal increases in the N contents of both blades and petioles. For musts, however, the total N concentration in the case of the N2 treatment was 50 mg/L higher than that of N0. No consistent effect of N fertilization on either grape or wine quality could be detected, but during one season the occurrence of bunch rot was enhanced by the highest N application. The application of P fertilizer caused appreciable increases in the P levels of blades, petioles, and musts, with the most sensitive indicator of P nutrition. At veraison the deficiency level for P in petioles appeared to be around 0.08%. Furthermore, the K concentrations in both blades and petioles of the P2 treatment was reduced, pointing to a P/K antagonism. Apart from this, P fertilization had little effect on either grape or wine composition. The K levels in blades, petioles, and musts of the K1 treatment were increased significantly over that of K0, while K2 caused a further increase of K concentration in blades and petioles but not in the must. In addition to this, K fertilization also tended to reduce the N levels of the musts. Both acidity and pH of musts from the K1 treatment were increased in comparison to that of musts from the K0 treatments, while little further response was found for K2. A petiole deficiency level of 1% for K seemed to be valid for South African conditions. Potassium nutrition was found to interact with arginine concentration in must, making the latter a doubtful indicator for N nutrition when levels of K in the soil are high.