The influence of NPK, phosphorus source and potassium foliar application on growth and fruit quality of Thompson Seedless grapevines.

摘要

A study was conducted in a drip irrigated vineyard in El-Salhia, Sharkia Governorate, Egypt to investigate the response of 11-year-old Thompson Seedless grapevines to various NPK fertilizer treatments, consisting of 2 N rates (60 and 80 kg/feddan), 2 sources of P (monoammonium phosphate and phosphoric acid) and foliar K (potassium thiosulfate, 2 ml/litre) applied during the veraison to harvest period. Within each N-rate, 6 NPK ratios were achieved. N at 80 kg/feddan improved vine growth and fruit composition more than N at 60 kg/feddan. However, improvements in vine productivity and cluster quality were related to NPK ratio, with an optimum achieved in response to 1:1:3 NPK. Monoammonium phosphate resulted in higher yields with better fruit composition than phosphoric acid. Spraying K at weekly intervals during the veraison to harvest stage improved the fruit composition, and so additional foliar K is recommended to sustain the advantages achieved by high NPK soil applications. [1 feddan = 0.42 ha].