Managing Broadleaf Weeds in Wheat (70 Days After Sowing)

Why Control Weeds at 70 DAS?

By 70 DAS, broadleaf weeds like Bathua (Chenopodium album), Pyaazi (Asphodelus tenuifolius), and Satyanashi (Argemone mexicana) have grown considerably. If left unchecked, they can cause:

• Yield Reduction: Weeds compete directly for essential resources, leading to smaller, fewer grains and reduced overall yield. Losses can be substantial, sometimes exceeding 30-40% in severe infestations.
• Nutrient Depletion: Weeds absorb valuable fertilizers meant for the wheat crop, making your investment less effective.
• Harvesting Difficulties: Dense weed growth can interfere with mechanical harvesting, increasing costs and grain losses.
• Pest and Disease Hosts: Some weeds can harbor pests and diseases, which can then spread to the wheat crop.

Recommended Herbicides and Application

At 70 DAS, the wheat crop is relatively mature, so selecting herbicides that are safe for wheat at this stage but effective against established broadleaf weeds is critical. Always consult local agricultural extension services or product labels for precise recommendations and dosages, as these can vary based on region and specific weed species.

Important Considerations:

• Weed Size: Herbicides are generally more effective on younger, actively growing weeds. At 70 DAS, weeds are larger, so ensure the chosen herbicide is effective on established plants.
• Wheat Stage: Ensure the herbicide is safe for wheat at its current growth stage (e.g., tillering to jointing).
• Resistance: If you suspect herbicide resistance in your area, consider rotating active ingredients or using tank mixes (as recommended by experts).

Application Method and Best Practices

Proper application is key to herbicide efficacy and safety.

• Sprayer Calibration: Ensure your sprayer is correctly calibrated to deliver the recommended dose evenly. Uneven application can lead to poor weed control or crop damage.
• Nozzle Type: Use flat-fan nozzles for broadleaf herbicides to ensure good coverage of weed foliage.
• Water Volume: Use sufficient water volume (typically 150-200 litres per acre) for thorough coverage, especially for larger weeds.
• Weather Conditions: Apply herbicides on a calm, clear day. Avoid windy conditions (to prevent drift) and immediately before or after rain (which can wash off the herbicide). The soil should have adequate moisture for optimal herbicide uptake by weeds.
• Protective Gear: Always wear appropriate personal protective equipment (gloves, mask, protective clothing) when handling and applying herbicides.

Integrated Weed Management Approaches

While chemical control is the primary method at 70 DAS, integrating other practices can enhance long-term weed management:

• Crop Rotation: Rotating wheat with other crops can break weed cycles and reduce weed pressure over time.
• Timely Sowing: Sowing wheat at the optimal time allows it to establish quickly and outcompete weeds.
• Clean Seeds: Use certified, weed-free seeds to prevent introducing new weed species.
• Manual Weeding: For small patches or specific resistant weeds, manual weeding can be a targeted approach, though labour-intensive at this stage.

Post-Application Care and Monitoring

After herbicide application, monitor your field for several days. Look for signs of weed wilting, yellowing, or stunted growth, which indicate the herbicide is working. Also, observe the wheat crop for any signs of phytotoxicity (herbicide damage), such as yellowing or burning of leaves. If damage occurs, identify the cause (e.g., incorrect dosage, wrong herbicide, stress conditions) to prevent future issues.

Controlling broadleaf weeds in wheat at 70 DAS is a critical management step that can significantly protect your yield. By selecting the right herbicide, applying it correctly, and observing field conditions, farmers can effectively manage weed pressure and ensure a healthier, more productive wheat crop.