Effect of Thinning Treatments on some Physical and Chemical Fruit Characters of Barhy and Magdool Date Palm Cultivars

This investigation was conducted during 2017 and 2018 seasons on 10-years-old trees of date palm (Phoenix dactylifera L.) Barhy and Magdool date palm cultivars grown in a loamy sand soil at a El-Wahat Bahariya, 10 x 10 m away from each other and watered by drip irrigation system to compare the differences in their growth, fruit physical and chemical characteristics. The selected trees from the two cultivars devoted for such study were strong, healthy, grown under the same air conditions and received the same agricultural practices usually done for date palm strand thinning treatments (control, 5 10 20 and 40 %) and the spathe thinning treatments (20 % and 40 %).
The results of this study have shown that means of fruit set (%) and fruit physical parameters of the two cultivars expressed as fruit weight (g), fruit flesh weight (g), fruit length and fruit diameter (cm)  were significantly improved by the various used combinations, with some exceptions compared to the control means in the two seasons. The highest values was for strand thinning treatment (40 %) and (10, 20 & 40 %) in fruit set (%) in Barhy cv, as well as (40 %) of strand thinning treatment and (40 %) in spathe thinning treatment in both seasons.  Also, the thinning treatments (5 % & 10 %) and (10 %) and (5, 10, 20 and 40) the best of fruit weight of Barhy and Magdool, in both seasons, respectively. As well as non significant in fruit/thinning (20 and 40 %) with both Barhy and Magdool cvs., in both seasons of study. The best results for fruit flesh weight with the thinning treatment (5%) and  (10, 40 and 5 %) and (20 %) with Barhy cv., also, (5 and 5 or 10%) and non significant between (20 and 40 %) for Magdool cv., for the specific effect; the highest values for the interaction effect between thinning treatment (bunch thing x fruits/strand) (5 % or 10 % x 20 %) and (5 % x 40 %) for Barhy and Magdool cvs. In the first season (2017); in the second season (2018)  (10 x 20 %) with Barhy cv., (5, 10 % x 20 or 40%) with Magdool cv. The best results for fruit length (cm) were the thinning treatments (5 %) and (20 %), also the interaction treatment with (5 % x 20 %) for Barhy cv., in both seasons. On the other side, the highest values from the thinning treatments (5, 10, 20 and 40 %) and (40 %) as well as (10 % x 40 %) in interaction effect in 2017 and 2018 seasons.  The best values was the specific effect for fruit diameter (cm) was non significant in the two cultivars (Barhy and Magdool) date palm, the superiority treatment for the interaction effect was with (5 % x 20 or 40 %) in the two cultivars in both seasons. The highest values for the total sugars and TSS for the thinning treatments (10 %) and (10 & 20 %), also non significant in (20 % or 40 %) in both seasons of study. As well as the combination treatments there variance in the two parameters and seasons. The acidity parameters non significant in all thinning treatments specific and combined in two seasons.      
Hence, it can be recommended to thinning of date palm cvs. Bary and Magdool grown in sand loamy soil, (5, 10, 20 and 40 %) or (20 or 40 %) depending on every variables during the growing season to get the best results for fruit physical and chemical quality of the resulted date palm.