Effect of nano-fertilizer on cluster characteristics of table grapes

Table grapes are considered among the most valuable agricultural products supplied to the Lebanese market. Implementing adaptive strategies is important to improve grape quality and increase its competitiveness to meet the market demand. This study was carried out through two successive seasons (2019 and 2020) in order to compare the effect of application of two concentrations of nano-fertilizer to that of the control on several productive traits of ‘Tfeifihi’ table grape. Three treatments were applied: conventional fertilizer (control) applied twice, Biozar Ca+B applied twice in two concentrations: 3 and 5 g L^‑1. Date of veraison and harvest, cluster weight, cluster length and width, cluster compactness, number of berries per cluster, and harvest date were evaluated. No significant difference was detected in phenological dates among all treatments. The highest cluster weight was determined in the control treatment in the first year and in Biozar Ca+B with 3 g L^‑1 in the second year. Biozar Ca+B applied in low concentration (3 g L^‑1) increased cluster weight 0.166 kg compared to control. However, differences were statistically not significant in both years. Average width of cluster, average length of cluster, average number of berries per cluster and cluster compactness were not significantly different in all treatments. The greatest cluster compactness was detected in 3 g L^‑1 Biozar Ca+B. In the latter treatment, both veraison and harvest dates were delayed by 6 and 4 days compared to 5 g L^‑1 Biozar Ca+B, respectively. Hence, Biozar Ca+B applied in low concentration (3 g L^‑1) enhanced the cluster quality of table grapes more than its application in a high concentration (5 g L^‑1). This suggests that high concentrations of nano-particles may negatively affect grapevine productivity.