The effect of boron levels in nutrient solutions on fruit production and quality of greenhouse tomatoes

Abstract

Insufficient fruit set of tomatoes owing to poor pollination in low cost greenhouses is a problem in South Africa, as bumblebee pollinators may not be imported. Since sub-optimum boron (B) levels may also contribute to fruit set problems, this aspect was investigated. Greenhouse tomatoes were planted in acid-washed river sand. Four nutrient solutions with only B at different levels (0.02; 0.16; 0.32 and 0.64 mg l^-1) were used. Leaf analyses indicated that the uptake of Ca, Mg, Na, Zn and B increased with higher B levels. At the low B level, leaves were brittle and appeared pale-green and very high flower abscission percentages were found. Fruit lacked firmness at the low B level and this problem worsened during storage. At the 0.16 mg kg^-1 B-level, fruit set, fruit development, colour, total soluble solids, firmness and shelf life seemed to be close to optimum. The highest B-level had no detrimental effect on any of the yield and quality related parameters. However, using ‘Solubor’ as a source of B, high levels decreased soluble Mn concentrations in nutrient solutions, probably owing to the precipitation of insoluble MnO₂. This was reflected in reduced leaf-Mn concentrations.