ABSTRACT
This investigation was carried out for two successive seasons (2017 & 2018) in a private vineyard located at El-Nubaria region, El-Behira governorate, Egypt to study the effect of summer pruning practices and magnesium (MgSO₄) spray on the microclimate, vegetative growth, yield and bunch quality of Flame Seedless grapevines. The vines were seven years old, grown in a sandy soil, spaced at 2 X 3 meters apart, irrigated by the drip irrigation system, cane-pruned and trellised by the Spanish Parron system. The vines were pruned during the first week of January in both seasons of the study so as to maintain a load of 90 buds/vine (9 canes X 10 buds/vine).
Nine treatments were carried out as follows: control (untreated vines), pinching the main shoots, defoliation, foliar spraying with 1% MgSO₄ once, foliar spraying with 1% MgSO₄ twice, pinching + foliar spraying with 1% MgSO₄ once, pinching + foliar spraying with 1% MgSO₄ twice, defoliation + foliar spraying with 1% MgSO₄ once as well as defoliation + foliar spraying with 1% MgSO₄ twice. Pinching the main shoots treatment was applied just after fruit set stage, while defoliation treatment was carried out at veraison stage. Foliar spraying with 1% MgSO₄ was applied either once just after fruit set stage or twice after fruit set stage and two weeks later.
The results showed that all summer pruning and magnesium spray treatments either alone or in combination among them had the best results in comparison with control in both seasons. Pinching the main shoots + foliar spraying with 1% MgSO4 twice recorded the best canopy microclimate, which reflected in achieving the highest yield and its components, improving the physical and chemical properties of berries, ensuring the best vegetative growth traits and increasing leaf content of total chlorophyll, nitrogen, phosphorus and potassium and cane content of total carbohydrates for Flame Seedless grapevines.