Thinning treatments affect yield, fruit quality and skin separation of ‘Medjool’ date palm grown in semi-arid conditions in Jordan

Date palm (Phoenix dactylifera L. ‘Medjool’) cultivation expanded very fast in the last few decades. Increased fruit size and high nutritive value were major quality characteristics that make it ranked first among other cultivars in Jordan. Skin separation is a major physiological disorder that lowers the commercial quality of ‘Medjool’ date palm. This study was undertaken for two growing seasons in two major areas of date palm production in Jordan to test for the effects of fruit thinning on enhancing fruit quality and reducing the incidence of skin separation. Six different fruit thinning methods were practiced by; removing 25% of strands number per bunch (T1), shortening strands by removing one third of strand length from terminal tips (T2), removing one third of central strands per bunch (T3), removing 50% of individual fruits per strand (T4), combining both shortening one third of total strands from terminal tips and removing one third of central strands (T5) and control non-thinned fruits (T6). Average fruit yield and bunch weight were significantly lower in response to all thinning treatments as compared to the control and the reduction increased by increasing the level of thinning. Fruit length, fruit weight, and average fruit diameter was the highest under fruit thinning (T5, T4). Fruit thinning resulted in significantly higher percentage of first grade fruits with lower levels of skin separation than control non-thinned fruits. Moreover, thinning treatments resulted in higher total soluble solids (TSS) of ‘Medjool’ fruits with values ranging from 60.0% (T6) to 71.0% (T4). We suggest fruit thinning at the beginning of kamri stage improved ‘Medjool’ fruit quality and lower skin separation percentage and, hence, help in enhancing the commercial value and marketability of this valuable date palm.