Precision in Weed Control

Definition; Precision weed control is the use of site-specific, targeted, and resource-efficient technologies to manage weeds, reducing reliance on blanket herbicide applications and manual weeding.
It ensures weed suppression with minimal crop damage, lower input costs, and environmental safety.

Objectives

• Detect and control weeds only where they occur.
• Reduce herbicide use and cost.
• Minimize environmental contamination.
• Avoid crop injury.
• Delay the evolution of herbicide resistance.

Approaches to Precision Weed Control

(i) Mechanical Precision

• Use of precision hoes, robotic weeders, and laser-guided cultivators.
• Implements like inter-row rotary weeders used in line-sown crops.

(ii) Chemical Precision

• Site-Specific Herbicide Application (SSHA): Herbicides applied only where weeds are present using GPS/GIS mapping.
• Smart Sprayers / Spot Sprayers: Equipped with sensors and cameras to detect green patches (weeds) and spray only on them (e.g., John Deere See & Spray technology).
• Herbicide-tolerant (HT) crops: Enable precision use of broad-spectrum herbicides like glyphosate.

(iii) Biological Precision

• Use of bio-herbicides or beneficial insects targeted only on problematic weeds.
• Example: Zygogramma bicolorata beetle on Parthenium.

(iv) Cultural Precision

• Use of precision sowing and row spacing so that inter-row weeding can be done effectively.
• High-density planting of competitive crops to suppress weeds naturally.

(v) Digital & Smart Technologies

• Drones: For aerial herbicide spraying with controlled dosage.
• Machine Vision & AI: Cameras + AI detect weed species and guide robotic sprayers.
• GIS Mapping For weed density monitoring.

Advantages

• Saves 30–70% herbicide use.
• Reduces weed–crop competition during critical period.
• Lower labor requirement compared to manual weeding.
• Prevents weed shifts & herbicide resistance by rotating control measures.
• Environmentally safe – less chemical load.

Limitations

• High initial cost of smart sprayers/robotic weeders.
• Requires technical expertise.
• Limited adoption in smallholder systems of India.

Facts for ASRB NET

Weeds cause 30–40% yield loss in field crops (up to 80% in dryland farming).
Precision weed control reduces herbicide cost by 40–60% compared to blanket application.
Critical crop–weed competition period (India, ICAR):

• Wheat → 30–45 DAS
• Maize → 20–40 DAS
• Soybean → 15–30 DAS
  In drylands, precision inter-row weeding + moisture conservation increases yield by 15–20%.
  AI-enabled “Green-on-Green” sprayers can differentiate crop vs weed and selectively spray (e.g., cotton, soybean).