Zinc deficiency (Khaira) in paddy
Zinc deficiency, also called Khaira disease, is the most common micronutrient disorder of flooded rice and the single most widely reported micronutrient constraint to Indian paddy productivity. Without correction it causes stunting, delayed tillering and increased spikelet sterility.
Identification and symptoms
Symptoms typically surface on the second or third leaf, two to three weeks after transplanting. Older leaves develop brown blotches and rusty streaks; younger leaves show leaf-base chlorosis. Affected plants are stunted, with reduced tillering, and the canopy often turns brick-red, leading to local confusion with red-leaf or 'erra rogam' symptoms. In severe cases the disorder reappears at the boot stage and increases panicle sterility.
Causes
Deficiency is favoured by neutral to calcareous and sodic soils, peaty soils, continuous flooding (which lowers Zn availability through redox chemistry) and soils with high phosphorus or silicon status that antagonise zinc uptake. Rabi/yasangi crops in north Telangana express the deficiency earlier - often within 15 days - because cold soils further depress Zn uptake.
Management
- Soil application: 10-25 kg ZnSO4.H2O per hectare (or 20-40 kg of the heptahydrate) broadcast and incorporated before transplanting.
- Root dip: dipping seedling roots in a 2-4% ZnO suspension for one hour before transplanting (Transplanting Paddy).
- Foliar correction: 0.5% ZnSO4 sprayed twice at 15-day intervals once symptoms are visible, often combined with the standard tillering spray window (Paddy Tillering Spray 25 50 Dat).
- Nursery prevention: address chronic deficiency at the nursery stage (Paddy Nursery Management) by adding ZnSO4 to nursery beds.
Related entries
See also: Paddy Nursery Management, Transplanting Paddy, Paddy Panicle Stage Fertilization, Paddy Tillering Spray 25 50 Dat, Brown Spot Paddy.
References
- Zinc (Zn) deficiency. IRRI Rice Knowledge Bank.
- Zinc fertilizer application in rice crop. Indian Farming (ICAR).