Boron Effects on Fruit Set, Yield, Quality and Paternity of Hass Avocado

Abstract

Boron plays a critical role in pollination and fertilization and can affect fruit set and yield. We applied 0 g, 15 g (manufacturer recommendation) or 30 g boron pre-flowering to Hass avocado trees to determine the effects on fruit set, fruitlet paternity, yield, fruit size, mineral nutrient concentrations and fatty acid composition. The boron applications did not significantly affect the initial fruit set at 3 or 6 weeks after peak anthesis or the proportions of self-pollinated fruitlets or mature fruit. Approximately 88–92% of the mature fruit were self-pollinated. However, applying 30 g boron per tree reduced the fruit set at 10 weeks after peak anthesis by 56% and the final yield by 25%. Attaining > 90% of the maximum yield was associated with foliar boron concentrations being below 104 mg/kg at 6 weeks after peak anthesis and between 39 and 68 mg/kg at 28 weeks after peak anthesis. Applying 15 g boron per tree increased the fruit mass by 5%, fruit diameter by 2%, flesh mass by 9%, flesh boron concentration by 55%, and the relative abundance of unsaturated fatty acids by 1% compared with control trees. Applying the recommended amount of boron provided a good yield of high-quality avocado fruit but applying boron at double the recommended rate reduced the yield.

Hyperspectral Imaging of Adaxial and Abaxial Leaf Surfaces for Rapid Assessment of Foliar Nutrient Concentrations in Hass Avocado

“…Nutrient toxicities in avocado can also occur due to the excessive use of fertiliser. For example, B is a critical nutrient for avocado fruit set and yield, but high B concentrations can cause fruitlet abscission and reduce yield [36]. Rapid nutrient assessment tools such as hyperspectral imaging could help growers detect nutrient deficiencies or toxicities in crops in real time, reduce fertiliser costs and manage nutrient applications more efficiently.…”

“…Leaves were collected from 30 Hass trees located at the Eastridge avocado orchard (25 • 13 25 S 152 • 18 54 E), near Childers, Queensland, Australia. These trees were used in a previous complementary study on the effect of boron applications on avocado fruit set, yield and quality [36]. Four heterogeneous leaves were randomly collected from each experimental tree on each of four occasions: 0, 6, 10 and 28 weeks after peak flower anthesis.…”

“…Nutrient levels within the avocado tree need to be sufficient to meet specific physiological demands during each stage of vegetative growth, flowering and fruit development [35]. Monitoring and maintaining nitrogen, phosphorus, potassium and boron concentrations during fruit set and development are critical to sustaining avocado yield [34][35][36]. Rapid assessment tools such as airborne laser scanning have been used to estimate the crown area, crown volume and tree count in avocado orchards [37], and HSI has been used to determine avocado fruit maturity and flesh nutrient concentrations [18,38].…”