Effect of soil boron application on gummosis and leaf boron content of mango (Mangifera indica L.) cvs. Khieo Sawoei and Nam Dok Mai

Boron (B) deficiency is a widespread and common nutrient disorder of agricultural and forestry crops in Thailand. To correct B deficiency in mangoes (Mangifera indica L.), a study was conducted to evaluate the effectiveness of soil application in raising leaf B concentrations in two cvs, Khieo Sawoei and Nam Dok Mai. Borax (11% B) was applied to the soil beneath trees at 0, 15, 20, 25 g m(-1) of canopy diameter (split into three applications). When B applications were given in the summer (wet season) the response was rapid, with leaf concentrations increasing by 93.6 and 75.6% at the highest rate for 'Khieo Sawoei' and 'Nam Dok Mail, respectively, 5 months after treatment. There was no evidence of phytotoxicity. Gummosis, a condition of resin ooze from splits that develop on major limbs and trunks in B deficient trees, decreased in 'Khieo Sawoei' trees that received borax at either 20 or 25 g m(-1) of canopy diameter.