Symptoms
Deficiency symptoms are visible on younger leaves and on the growing point of the plants.
The leaves are light green and mottled, the new developing leaves have an asymetric shape with uneven margins and necrotic spots.
Furthermore the terminal buds are dying back. The tree produces secondary branches resulting in a deformed, fan-shape bush.
Reasons
Boron deficiency
Calcium deficiency also shows bronzing of the youngest leaves and necrosis of emerging leaves, but bronzing starts at the margins and leaves are cupped downwards. Emerging leaves do not have an asymetric form.
Boron deficiency made worse by
Sandy soils
Alkaline soils
Soils low in organic matter
High levels of nitrogen
High levels of calcium
Cold wet weather
Periods of drought
Boron is important for
Improves flower bud development
Better quality of flowering
Improves the 'set' of fruit (beans)
Yara recommended fertilizers for Boron
YaraVita BORTRAC 150
Coffee: 1 l/ha early in the growing season, pre-flowering and again post-harvest. Water rate: 200 to 500 l/ha.