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Zinc deficiency in paddy (khaira)

Khaira disease of rice is the classic expression of zinc deficiency. It was first described in north-Indian calcareous soils by Y.L. Nene, who also demonstrated the foliar zinc-sulphate cure that became the standard correction. The disorder is one of the most widespread micronutrient deficiencies in Indian paddy and is a leading contributor to crop-level Hidden Hunger Micronutrients.

Identification and symptoms

Symptoms typically appear 15-20 days after transplanting as rust- or brick-coloured inter-veinal spots on older leaves, often on the second or third leaf from the top. Affected plants show stunted growth, poor tillering and, in severe cases, sterile panicles. Symptoms may also recur at the boot stage. The yellow-to-brick-red discolouration can resemble red disease (locally erra rogam), and laboratory confirmation through soil or tissue testing is helpful in mixed-symptom fields.

Host crops and predisposing conditions

The deficiency is aggravated on alkaline, calcareous, high-phosphorus or sodic-water-irrigated soils, where free zinc availability is low. Continuous transplanted paddy on the same plot, prolonged submergence and high P fertiliser regimes also depress zinc uptake. In rabi (yasangi) paddy, cold weather can intensify symptom expression. Diagnosis is supported by routine Soil Testing under the Soil Health Card scheme, which reports available zinc.

Damage and management

Severe khaira can reduce tillering by half and cut grain yield substantially through panicle sterility. Standard correction is soil application of 10-25 kg/ha zinc sulphate monohydrate (ZnSO4.H2O) or 20-40 kg/ha zinc sulphate heptahydrate (ZnSO4.7H2O) at basal, plus a 0.5% foliar zinc-sulphate spray when symptoms persist after transplanting. Where soil pH is the underlying driver, parallel Soil Ph Management reduces the recurrence risk. Field water management (Paddy Water Management) influences zinc redox chemistry and uptake during the season.

See also: Hidden Hunger Micronutrients, Soil Testing, Soil Ph Management, Paddy Water Management.

References

  1. Correcting Micronutrient Deficiencies in Paddy. Indian Council of Agricultural Research.
  2. Zinc deficiency. IRRI Rice Knowledge Bank.
  3. Rice Zinc. TNAU Agritech Portal.