Symptoms of iron deficiency first appear in the youngest leaves. It is characterized by the yellowing (chlorosis) of upper leaves, with the midrib and leaf veins remaining clearly green (interveinal chlorosis). At later stages, if no measures are taken, the whole leaf turns whitish-yellow and brown necrotic spots start to appear on the leaf blade, often leading to the development of necrotic patches on the margins. Affected areas can easily be identified from a distance in the field. Plants with iron deficiency are stunted in growth and potentially produce lower yields.
Iron deficiency can be a serious problem in leached tropical soils or in poorly drained soils, mostly under cool, damp springs. Sorghum, corn, potatoes, and beans are the most severely affected crops whereas wheat and alfalfa are the least sensitive. Calcareous, alkaline soils (pH 7.5 or higher) derived from limestone make plants especially prone to iron deficiency. Iron is important for photosynthesis and for the development and maintenance of root nodules in legumes. Therefore, iron deficiency severely depresses nodule mass, nitrogen fixation, and crop yield. The estimated critical level is around 2.5 mg/kg of plant dry tissue. The deficiency of iron also increases the uptake and accumulation of cadmium in plants.
Smallholders may use a leaf fertilizer made of nettle slag and algae extract. Application of animal manure, peat and composts also add iron to the soil. Plant dandelions in the proximity of your crops, since they make iron available to nearby crops, especially trees.
- Use fertilizers containing iron (e.g. Ferrous sulphate Fe 19%). - Consult your agricultural advisor to know the best product and dosage for your soil and crop. - It is recommended to do a soil test before the start of the cropping season to optimize your crop production.