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Heatwave Threat to Wheat Crop
Context:
India has recorded its warmest February in 124 years, raising alarms over the impact of extreme heat on the country’s agricultural sector, particularly the wheat crop.
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- The India Meteorological Department (IMD) has already warned that March will experience above-normal temperatures and more frequent heatwaves, which coincide with the wheat harvest season.
- Wheat, India’s second-most consumed crop after rice, faces a significant threat from these rising temperatures, which could harm both the crop yield and quality.
What is a Heat Wave?
- A Heat Wave is a period of unusually high temperatures, above the normal maximum temperature typically experienced during the summer season in the North-Western parts of India.
- Heat waves generally occur between March and June, and in rare cases, they can extend into July.
- Heat waves are becoming more frequent and intense globally due to climate change. In India, the frequency and severity of heat waves have increased in recent years, leading to more health-related casualties.
- Health Impacts: Dehydration, heat cramps, heat exhaustion, and heat stroke are common health problems caused by heat waves.
Wheat Production in India:
- Primary wheat-growing regions: Wheat is predominantly grown in the northwestern Indo-Gangetic plains, including Uttar Pradesh, Punjab, Haryana, and Madhya Pradesh.
- Wheat season: The crop is sown between October and December and harvested between February and April in the rabi season.
- Government procurement target: India set a wheat procurement target of 30 million tonnes for the 2025-2026 rabi marketing season, lower than previous years, despite a forecast of 115 million tonnes production for 2024-2025.
- Wheat export ban: In May 2022, India banned wheat exports to manage domestic supply after Russia’s invasion of Ukraine disrupted global wheat availability.
Climate Change and Heat Stress on Wheat
- Increasing global warming: Rising temperatures are affecting wheat growth, particularly during the reproductive and grain-filling stages.
- Study findings: A 2022 study published in the International Journal of Molecular Science highlighted that heat stress reduces grain production and quality by altering biological processes such as photosynthesis, respiration, and oxidative damage.
Stages of Wheat Growth and Heat Sensitivity
- Germination to Emergence: This is the phase where the seed grows until the seedling breaks through the soil surface.
- Growth Stage 1: This stage spans from emergence to double ridge, where the plant produces primordial leaves and begins to form spikelets, the flowering structures.
- Growth Stage 2: From double ridge to anthesis, the plant shifts from vegetative to reproductive growth. This is when wheat is most vulnerable to heat stress.
- Growth Stage 3: This phase, from anthesis to maturity, marks the grain-filling period.
- Extreme heat is particularly damaging during the reproductive stage (Growth Stage 2) when heat waves disrupt the plant’s ability to develop properly.
Impact of Heat Stress on Wheat
- Accelerated flowering and ripening: High temperatures shorten the grain-filling period, resulting in lighter grains with lower starch accumulation, leading to reduced wheat output.
- Lower-quality grains: Heat causes higher protein content but lower starch in grains, making them harder and affecting milling quality.
- Economic consequences: Reduced grain weight and quality issues lead to lower market prices for farmers.
- Cascading effects: In response to low yields, farmers may overuse fertilisers and fungicides, worsening the long-term impact of heat stress.
Warming Indian Ocean and Altered Monsoon
- Indian Ocean warming: A study from the Indian Institute of Tropical Meteorology (2024) warns that the Indian Ocean is warming at an accelerated pace, which is expected to lead to a “near-permanent heat wave state” by the end of the century.
- As a result, the frequency of marine heat waves is projected to increase dramatically, from an average of 20 days per year to 220–250 days annually.
- Impact on monsoons: The warming Indian Ocean alters India’s monsoon patterns, delaying the start of the rabi season and exacerbating the risk of heat stress for wheat.
Adaptive Strategies and Solutions
- Addressing food security: Policymakers must focus on adapting agricultural strategies to cope with heat stress, ensuring food security for India’s population.
- Improved crop management: Recommendations include early sowing of crops in areas expected to face early heat waves and introducing improved wheat varieties with shorter growth cycles.
- Climate-resilient wheat varieties: Development and adoption of heat-resistant varieties to cope with rising temperatures are essential but not a complete solution to the broader climate crisis.
- Support for farmers: Immediate policy measures such as compensation for heat-related losses and long-term solutions like efficient resource management and crop insurance can help mitigate the impact of heat stress on wheat.
- Research and technology: Scientific research, technological advancements, and better weather forecasting will help farmers make more informed decisions regarding crop management.
