Nutrient Management Research Database

Leaf concentrations of boron (B) were effectively increased via foliar application. Foliar B applications ameliorated deficiency systems associated with ‘blossom blast’ in the spring and fruit corking and cracking at harvest. Fertigated B was mobile within the soil and it was relatively easy to increase leaf and fruit B concentrations via fertigation of modest rates of 0.34 g per tree. The ready response of tissue B concentrations to fertigated B suggests caution is required to select moderate B application rates in order to avoid toxicity when fertigating B. There were minor differences in leaf B concentrations among ‘Gala,’ ‘Fuji,’ ‘Fiesta,’ and ‘Spartan’ apple cultivars during the field trails. Nevertheless, in general, all cultivars responded similarly to B treatments, including non-application or application via foliar spray or fertigation.

• The effects of boron (B) application in a high density (674 trees/ac) apple orchard was observed for 4 years.
• B was either not applied or supplied through either foliar applications or a fertigation system.
• Leaf B concetration was measured, and the prevalence of  B deficiency symptoms, including 'blossom blast,' were observed.

• Leaf concentration of N was effectively increased as a result of foliar B application.
• B defieincy symptons, including blossom blast, corking, and cracking at harvest were effectively reduced by foliar B application.
• Tree tissue B concetrations increased at relatively low levels of B fertigation (0.5 lbs/ac).
• Follwing B applied via drip lines, leaf B levels suggested that precautions were needed to avoid B toxicity.

There is a narrow gap between levels of B sufficient for optimal crop production and levels toxic for trees.