Iron deficiency symptoms first appear on the younger leaves at the top of the plant. Excessive levels of the Phosphorus in the soil can trigger Iron deficiency.
Yellowing of the young leaves, while the veins remain green. In severe cases, the entire new leaf may become yellow and can turn almost white. Growth is usually stunted. In sorghum, maize and other grasses the leaves may have a striped appearance covering the entire length of the leaf.
Functions in plant:
Plays an important role in production of chlorophyll. Involved in respiration of plants. Serves as a catalyst in cell division and growth processes.
Mobility in plant: Very immobile deficiencies occur on new leaves.
Mobility in soil: Immobile.
Influence of pH: Unavailable at high pH's. Deficiencies are closely associated with alkaline soils.
Factors affecting level: High pH; calcareous soils; high organic matter; erosion or land levelling which removes organic iron.
Factors affecting utilisation: Those above; poor aeration; low temperatures; heavy compaction; high phosphate fertilizers in a band may depress iron; excess Zn, Mn, or Cu depress iron.
Adequate plant level: Cotton 40-500 ppm, rice 20-200 ppm, maize 40-500 ppm, grape 60-200 ppm, Lemon 60-100 ppm, watermelon 50-300 ppm.
Lower the pH by application of heavy rates of sulphur - greater efficiency is obtained when nitrogen is applied at the same time.Sprays: iron sulphate applied at 1 kg per 400 litres water per hectare. Chelates will give profitable aand better results. All chelates are not the same.
Fe++ is generally considered available, whilst Fe+++ is not.