Effect of Boron and Ascorbic Acid on Growth, Flowering and Productivity of Almond Trees under Rain-fed Conditions

Abstract

The present study was conducted in a private almond orchard at Marsa Matrouh Governorate, Egypt during three consecutive seasons of 2021, 2022 and 2023 of about 10 years old, "Umm al-Fahm" almond trees (Prunus dulcis (Miller) D.A. Webb) budded on Bitter almond rootstock and planted at 7x7 m apart. The trees were grown in sandy loam soil under rainfed conditions. This investigation was designed as in a factorial experiment with two factors i.e. the first factor six foliar spray treatments i.e. control, boric acid (H3 BO3) (B) at two concentrations (150 and 300 ppm), ascorbic acid (C6 H8 O6) (AsA) at two concentrations (750 and 1000 ppm) and boric acid (B) at 300 ppm plus ascorbic acid (AsA) at 1000 ppm and the second factor consisted of two application dates of the tested treatments, 15th September and 15th December on vegetative growth characteristics, fruit set percentage, yield and fruit quality. The results showed 300 ppm boron plus 1000 ppm ascorbic acid foliar spray gave the highest values for vegetative growth characteristics (shoot length increase, number of shoots/branch, number of leaves/shoot, leaf chlorophyll content and leaf area), fruit set percentage, yield , fruit quality (kernel weight, kernel length and kernel width) application date of foliar spray in 15th September had the highest significant effect on number of shoots/branch, leaf chlorophyll content in both seasons, and both leaf area and fruit set percentage in first season) fruit quality (kernel weight and kernel length in both seasons) than that foliar sprays on 15th December , but had no significant effect on shoot length increase, number of leaves per shoot, yield , kernel weight in both seasons also fruit set percentage in second season. Furthermore, the interaction between foliar spray treatments and application dates of foliar sprays indicated that 300 ppm boric acid plus 1000 ppm ascorbic acid foliar spray at 15th September recorded the highest values for vegetative growth characteristics fruit set percentage, yield and fruit quality.