Effect of foliar- and soil-applied boron in deciduous fruit orchards 2: apricot and peach

Abstract

Between autumn 1996 and May 1998 a variety of boron (B) treatments were applied to mature apricot and peach trees in Western Cape orchards on soils containing 0.2 to 0.7 mg B kg⁻¹. Leaf B levels in the B treatments averaged 11.1% higher than the controls in the apricot, and 22.8% higher in the peach orchard. Average apricot fruit B levels in the B-treatments were 47% higher than the controls in 1998. In the B-treated peach trees the average fruit B level was 63% higher than the controls in 1997, and 106% higher in 1998. Leaf and fruit B levels were not affected, relative to non-B treated controls, by single spring B spray applications at concentrations up to 26.0 g B 100 I¹, or by treatments in which a single spring B spray at 19.5 g B 100 I⁻¹ was supplemented by a single autumn B spray containing up to 97.5 g B 100 I⁻¹. The application of four early-season sprays at 31.2 g B 100 I⁻¹, followed by a single autumn spray at 41.6 g B 100 I⁻¹, or by an autumn soil application of either calcium borate at 2.10 g B tree⁻¹, or borax at 1.13 g B tree⁻¹, resulted in excessively high fruit B levels in peach. In the absence of spring B sprays both apricot and peach showed increased leaf and fruit B levels where calcium borate was applied each autumn at 2.10 g B tree⁻¹. The peach fruit B levels were excessively high where calcium borate was applied at 2.80 g B tree⁻¹. Apricot and peach leaf and fruit B levels correlated with 0.02 M CaCI₂- extractable soil B. Peach fruit calcium levels decreased with increasing soil, leaf and fruit B levels.

Keywords:

• apricot
• boron
• orchard nutrition
• peach