The effects of different nitrogen doses on yield, quality and leaf nitrogen content of some early grape cultivars (V. vinifera L.) grown in greenhouse
Nitrogen deficiency is a worldwide problem, causing restrictions in productivity of many horticultural produces. Particularly, the issue is compounded when the greenhouse production is employed. Therefore, reliable knowledge on proper application of nitrogen ensures not only satisfactory yield but also balanced vegetative and reproductive growth in plants. This study was thus conducted to investigate the effects of different nitrogen doses (10, 20 and 30 kg N da-1) on some quality properties with petiole nitrogen content of grape cultivars ‘Early Cardinal’ (EC), ‘Yalova Incisi’ (YI) and ‘Ergin Cekirdeksizi’ (ER) grown in plastic greenhouse for two years. Overall results indicated that cluster weight, cluster length and yield values increased depending on the nitrogen doses. On the other hand, increasing nitrogen applications generally resulted in higher petiole nitrogen content. The highest petiole nitrogen values were obtained from the treatment of 30 kg N da-1 for two phenologycal periods (1.29 and 1.59% for full bloom and veraison, respectively). Considering the general investigations, 20 kg N da-1 application could be recommended in terms of nitrogen supply under such conditions.
Key words: Grapevine, nitrogen fertilizing, yield, petiole analysis.