Bunch Bagging as a Useful Means to Overcome Harsh Climatic Conditions and Improve Yield and Quality of Date Palm Fruits

Date palm trees grown in hot arid zones are facing abiotic environmental stresses. Both tree productivity and fruit quality characteristics responded negatively, especially the weight and size of fruits. Bagging is a physical technique commonly used with many crops to protect the fruits from diseases and pests and to improve the micro-climate in which the fruits are grown. This study was conducted during the 2016 and 2017 seasons at the Research and Agricultural Experimental Station, King Saud University, Riyadh, Saudi Arabia. Growing degree days (GDD) calculated from a base temperature of 18 °C was used, based on average daily temperatures (Averaging Method). Different bagging materials were used to investigate their effect on yield and fruit quality of 14-year-old 'Khalas' date palm cultivar. Bunches were pollinated by placing 10 'Meghal' fresh male strands among female strands during both seasons. Two bagging materials (polyethylene and grill cloth) were used on bunches during the kimiri and khalal stages; bunches without bagging were used as the control. The GDD during different stages of fruit growth until harvest time was higher than the optimal threshold needed for fruit growth, especially during the kimiri stage (April and May), and accompanied by low relative humidity, which decreased the quality and yield of date fruits. All the bagging treatments improved yield, bunch weight, fruit weight, as well as total and reducing sugar contents as compared to the control treatment. The best results in physical properties and chemical properties resulted from polyethylene bagging treatments (perforated and permeable bags), which gave the highest average fruit weight (11.12 and 10.20 g) and the highest average TSS% (66.33 and 78.88) in both seasons, respectively. Additionally, under the conditions of the current investigation, bagging with polyethylene can be advised to increase the output and fruit quality of 'Khalas' fruits.