What is the difference between preplant, preemergence, and postemergence herbicide applications?

Herbicides are classified based on their timing relative to the planting and growth of crops. These categories help farmers manage weeds effectively throughout the growing season:12

• Preplant: These herbicides are applied to the soil or to existing weeds before the crop is planted. This method is often used to clear a field of weeds before sowing seeds.12
• Preemergence: These are applied after the crop has been sown but before the seedlings have emerged from the soil. Modern agricultural machinery can often incorporate these herbicides into the soil during the planting process.21
• Postemergence: These herbicides are applied after the crop seedlings have emerged from the soil.2

Choosing the correct timing is a critical component of weed management, as it ensures that the herbicide targets unwanted plants while minimizing harm to the desired crop.12