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Site Specific Nutrient Disorders
Zinc Deficiency
Areas affected
Zinc deficiency symptoms are commonly seen both in acid as well as alkaline soils where cassava is cultivated in India.
Deficiency symptoms
Interveinal chlorosis of younger leaves is the characteristic symptom of zinc deficiency. First, small white or pale yellow spots or patches appear in between the veins of leaves. The lobes of leaves become narrow, chlorotic and will curl upward. In case of severe zinc deficiency, tips of leaves become necrotic.

Zinc deficiency symptom on cassava leaf

Zinc deficient plant in acid soils

Zinc deficient plants in alkaline soils
Corrective measures
Apply 12.5 kg Zn / ha as ZnSO47H2O at planting or incorporate ZnO before planting (cassava). If the problem is found to be less severe, foliar application of 1-2% solution of ZnSO47H2O is very effective. Under alkaline conditions of Salem and Gujarat, for cassava, stake treatment is recommended since Zn supplied to soil is precipitated at high pH (6.7-8.0). Under such situations, dip the stakes of cassava in 2-4% solution of ZnSO47H2O for 15 minutes prior to planting or apply 1-2% solution of ZnSO47H2O as foliar spray.
 
Boron deficiency
Areas affected
Boron deficiency is seen in some acid soils where cassava is cultivated in India.
Deficiency symptoms
Since boron is highly immobile within the phloem, the symptoms of boron deficiency appear on growing tips of cassava. If plants are uprooted, we can see very poor lateral root development and death of root tips. The plants will become shorter by a reduction in intermodal length. At the growing tip of plants, leaves will be small and deformed with short petioles and gummy lesions on the petioles. Brown gummy lesions on the petioles at the leaf tip and on growing portion of stems is a symptom of boron deficiency.


Boron deficiency symptoms on cassava leaf

Boron deficiency symptoms on cassava stem
Corrective measures
In areas where boron deficiency seen, apply 10 kg / ha B as borax or dip the stakes in 0.5-1 % borax solution before planting cassava.
 
Magnesium Deficiency
Areas affected
Magnesium deficiency is found both in acid soils (Kerala, Andhra Pradesh) and alkaline soils (Tamil Nadu, Gujarat) where cassava is cultivated in India.
Deficiency symptoms
The lower leaves of magnesium deficient plants show interveinal chlorosis. At first the tips and margins of these lower leaves develop chorotic symptoms. Later on the symptoms spread inward covering the entire portion of the area in between the veins. In areas where severe magnesium deficiency is seen, the leaves become necrotic and develop whitish colour. Magnesium deficiency symptoms are common in soils where there is excessive amount of potassium.

Magnesium deficiency symptom on cassava leaf

Magnesium deficient plant
Corrective measures
In areas where magnesium deficiency is found, apply 20-50 kg Mg / ha as MgO, dolomite or MgSO4. If MgO and dolomite are used, broadcast and incorporate before planting since they are relatively insoluble. If MgSO4 is used, apply it as band application near plants shortly after planting since it is soluble.
Manganese deficiency
Areas affected
In alkaline soils of Tamil Nadu and Maharashtra, manganese deficiency commonly seen. Manganese deficiency is common in calcareous soils.

Deficiency symptoms
The typical symptoms of manganese deficiency are interveinal chlorosis of leaves in the middle portion of the cassava plant. Manganese deficiency symptoms will not be seen on youngest leaves and by which we can distinguish manganese deficiency from iron deficiency. In case of severe manganese deficiency, the leaves will become completely chlorotic.

Manganese deficiency symptoms on cassava leaf

Manganese deficient plant
Corrective measures
In manganese deficient areas, soil application of MnO or manganese sulphate or foliar spray of MnSO44H2O (1-2% solution) is recommended. Dip the stakes in 5% solution of MnSO4 4H2O for 15 min. before planting.
Iron deficiency

Areas affected
Iron deficiency is widespread in alkaline soils of Tamil Nadu and Maharashtra where cassava is grown.

Deficiency symptoms
Iron deficiency is characterized by chlorosis of younger leaves. First, the symptoms will appear in interveinal areas of leaves and later on all portions of leaves including veins will become chlorotic. In the case of iron deficiency, the green veins will become prominent in between the yellowish interveinal areas, while in the case of manganese deficiency, the boundary between green veins and chlorotic interveinal areas becomes diffuse. Iron deficient plants become stunted in growth, leaves will be smaller in size than normal leaves but will not be deformed.

Iron deficiency symptoms on cassava leaf

Iron deficient plant in Vertisols of Tamil Nadu

Iron deficient plant in Vertisols of Maharashtra
Corrective measures
Apply 1-2% FeSO4.7H2O solution as foliar spray. Dip stakes of cassava in 5% FeSO47H2O solution for 15 minutes before planting.
 
Central Tuber Crops Research Institute
Sreekariyam, Thiruvananthapuram, Kerala - 17