The effect of different boron applications on the leaf boron concentration, fruit set and fruit yield in a commercial mango plantation.
Coetzer L. A., Robbertse P. J., Janse van Vuuren B. P. H.
Author Affiliation: Margaretha Mes Instituut vir Saadnavorsing, Universiteit van Pretoria, Pretoria, South Africa.
Yearbook - South African Mango Growers' Association 12 : 48-51
Abstract : Six-year-old cv. Tommy Atkins trees were treated with foliar sprays (10 litres of solution/tree) of (1) Solubor at 3 g/litre, (2) 1% Wuxal [NPK + trace elements + IAA + vitamin B], (3) 1% Wuxal + 2 g Solubor/litre or (4) unsprayed control; or with soil applications of (5) 50 g Solubor in 20 litres of water/tree, (6) 80 g Solubex in 20 litres water/tree, or (7) control with no B application. The first foliar spray and the soil applications were made on 10 July; a second foliar spray was applied on 21 Oct. Data from various sampling dates are presented on contents of Ca and B in the leaves and inflorescences and on fruit set and fruit yields. Fruits were harvested from late Nov. There appeared to be no relation between B treatments and leaf Ca content, which ranged from 1.0 to 1.7% throughout the trial; Wuxal treatment was associated with a small increase in leaf Ca. Inflorescence Ca contents were much lower, the maximum being 0.7%; they increased from the first sampling (on 24 July) to the third (23 Aug.) in all treatments. Leaf B contents (mg/kg) were very low during the flowering period; from early Oct. onwards they increased significantly, except in controls. They were highest with treatment (1). After early Oct., when the fruits had set and were starting to develop, the intensity of the sink for B was reduced. Soil applications were less rapidly effective than foliar sprays. It is suggested that in cases where B is likely to be deficient, any soil treatment should be carried out at least 3 months before the onset of flowering. With foliar applications, between 2 and 3 sprays of 3 g Solubor/litre directed to the young growth should ensure that B reaches the summer flush and the young inflorescences.