Zinc Deficiency
Zincum Deficientia
About Zinc Deficiency
Zinc deficiency, historically known across South Asia as Khaira Disease, is the most widespread micronutrient disorder in wetland rice. Continuous soil submergence and high pH immobilize zinc into insoluble zinc sulfide and hydroxide forms, causing rusty-brown leaf blotching and stunted growth 2-4 weeks after transplanting.
Taxonomy & Features
- Khaira Disease Symptoms: Dusty, rusty-brown spots coalesce on the leaves, giving the crop a scorched, copper appearance.
- Stunted Rosette Growth: Short internodes force leaves to cluster together, forming a compact rosette.
- Delayed Panicle Emergence: Severely slows down crop development, resulting in uneven heading and empty grains.
Seasonal Outbreak Calendar
Outbreak risk and activity timeline for Zinc Deficiency based on seasonal climate patterns:
Prevention & Cure
Natural & Organic Methods
- Incorporate organic manures (well-composted FYM) mixed with zinc sulfate before transplanting.
- Allow the field to dry out temporarily to aerate the soil and release locked zinc.
Chemical & Professional Control
- Apply Zinc Sulfate (21% or 33% Zn) to the soil at 25 kg/ha during land preparation.
- Foliar spray of 0.5% Zinc Sulfate mixed with 0.25% lime or 2% Urea at 15-day intervals during early symptoms.
Frequently Asked Questions
What triggers Khaira disease (zinc deficiency) in rice paddies?
Khaira disease is triggered by prolonged soil waterlogging, high soil pH (>7.0), intensive multi-crop cropping without micronutrient replenishment, and high bicarbonate concentrations that bind soil zinc.
How do I distinguish Khaira disease from fungal Brown Spot?
Khaira symptoms appear as dusty, copper-brown blotches coalescing along leaf midribs 2-4 weeks after transplanting on stunted hills. Brown Spot features distinct oval lesions with yellow halos distributed across leaves at later growth stages.
What is the fastest emergency treatment for standing rice crops showing Khaira symptoms?
Foliar spray of 0.5% Zinc Sulfate heptahydrate (5g/L water) mixed with 0.25% slaked lime or 1% Urea. Spraying twice at a 7-day interval rapidly corrects foliage chlorosis within a week.
Recommended diagnostics based on crop family and symptoms:
Remedy Disclaimer & Safety Notice
This disease guide is for educational screening purposes only. Pathogen behavior, severity, and host susceptibility can vary dramatically based on seed variety, weather conditions, and regional microclimates. Chemical pesticides and organic treatments are subject to strict regional environmental regulations and registration mandates. Please verify all chemical registrations and review manufacturer safety labels carefully with local certified agronomists or agricultural extension service offices before applying.