Effect of foliar spray of yeast extract and potassium nitrate on yield and fruit quality on Ziziphus jujuba L. trees

The present study was conducted during the two successive seasons, 2017 and 2018, at King Saud University, Saudi Arabia, to investigate the effects of foliar sprays on Ziziphus jujuba trees by yeast extract at 1% and 2% and potassium nitrate (KNO3) at 1% and 2%. All treatments were foliar applied twice (December 15–January 15) in both seasons. Yield and fruit quality were studied. Treatments significantly improved yield, physical fruit and fruit chemical characteristics, moisture content, chlorophyll a, b and total chlorophyll by most tested treatments in both seasons than the control (water only). Yeast spray treatments significantly decreased juice content vitamin C (mg/100 g), while KNO3 spray treatments increased juice content vitamin C in both seasons. It can be concluded that foliar application with KNO3 at 2% recorded the best treatment to obtain the highest yield, fruit weight, flesh weight, fruit volume, fruit length and fruit diameter, while yeast extract at 2% treatment gave the highest TSS% and total sugar contents in this study.