Water stress: oldest leaves start to change colour
Nitrogen: Nitrogen aids plants in making proteins that are using for healthy foliage grow. Excess causes rapid grow but poor flowering. Deficiency causes stunted growth. Symptoms: at the beginning the oldest leaves start to get a uniform discoloration. All the leaves start to change in a second moment into a golden-yellow to nearly white colour.
Potassium deficiency: Translucent yellow to orange, black or necrotic spots. Most severe on the oldest leaves, and towards the tips. Accentuated by high nitrogen fertilization within the root zone that block the plant from uptaking this nutrient can lead to disease and general poor health.
Magnesium: On old leaves: broad chlorotic bands along the margins, only central portion of the leaves still green.
Manganese: On new leaves: frizzletop effect on leaves caused by high pH soils
Iron: New leaves are yellow – white. Green spots superimposed on oldest
Boron: Leeching stop relase B after a high rainfall or excessive irrigation. Lethal yellowing (‘Candidatus Phytoplasma palmae’ subgroup 16SrIV, strain A: Kingdom Bacteria, Division Firmicutes) Symptoms: premature drop of fruits, necrosis of flowers after changing colour. Foliar discoloration, leafs collapses falling down from the palm and no new leaves will appear. Disorders: Potassium deficiency will cause discoloration and premature death of the lowest leaves in the canopy. Boron deficiency in coconut will cause premature nut drop. However, nuts dropped due to boron deficiency will not have the discoloured, water-soaked appearance at the calyx (stem) end of the nut that is typical of lethal yellowing.