The effects of different nitrogen and potassium levels on yield and quality of two early grape cultivars grown in different soilless media

In this research, ‘Trakya ilkeren’ (Ti) and ‘Yalova incisi’ (Yi) cultivars in three growing media namely Pomza (basaltic tuff), cocopeat, perlite:peat (2:1) mixture were grown using Hoagland nutrient solution under plastic cover. Additionally, two nitrogen (N) levels (100 and 200 ppm) in Yi, and two potassium (K) levels (150 and 300 ppm) in Ti were tested. To obtain the effect of treatments, grape yield, cluster weight, length, width, berry weight, berry volume, total soluble solids (TSS), acidity, pH and mineral element levels of the leaves were examined. Considering grape yield and cluster weight, the best results were obtained from cocopeat and perlite:peat mixture for both cultivars. The concentrations of 100 ppm N in Yi and 150 ppm K in Ti gave higher values than the other treatments. For cocopeat × 150 K treatment, grape yield, cluster weight, TSS%, acidity% and pH was 32.4 t ha‑1, 374.7 g, 14.37, 0.584 and 3.47, respectively. In the same order, values of perlite:peat mixture × 150 K took place as 30.5 t ha(‑1), 352.6 g, 13.70, 0.582 and 3.55. In terms of N treatments of Yi cultivar, values in the same order mentioned above were 40.7 t ha(‑1), 407.8 g, 12.63, 0.405 and 3.67 for cocopeat × 100 N; 44.5 t ha(‑1), 445.4 g, 15.17, 0.413 and 3.82 for perlite:peat × 100 N treatment. Berry weight and volume were not clearly affected by the N and K levels. Results showed that the soilless culture can provide high yield for table grapes without negative effects on cluster and berry quality.