Related technologies of corn weed control (I) – closed weed control

As the weather warms, spring corn in northern regions is entering its growth phase. Corn weed control, such as barnyard grass, foxtail, tiger tail grass, redroot pigweed, amaranth, lambsquarters, nightshade, crabgrass, and duckweed, are common and problematic. They are our primary targets for control.

In corn fields with one annual crop, the standard approach is “pre-emergence and post-emergence” weed control.

“Pre-emergence” means applying herbicides after sowing but before seedlings emerge. This is also known as soil-applied weed control. “Post-emergence” refers to controlling weeds after seedlings have appeared. Today, let’s focus on pre-emergence control.

Pre-emergence weed control works by creating a herbicide layer on the soil. After application, the herbicide forms a layer or film. As weeds grow, their roots or shoots absorb the herbicide, causing death. Corn seedlings, however, are not affected because they contain an enzyme called corn ketone, which breaks down the herbicide.

For pre-emergence herbicides:

Single-agent herbicides are rarely used alone. Instead, herbicide mixtures are common. Combining different herbicides can expand control, enhance effectiveness, reduce amounts used, and lower costs. Typically, a mix of Acetochlor + Atrazine + 2,4-D or a combination product of these is used for soil treatment.

Timing is crucial:

1. Apply within 7 days after sowing, ideally within 3-4 days. This should be done before corn and weeds emerge. If weeds have already appeared, the herbicide may not be effective and could harm the corn.
2. Spray when the average temperature is 12°C. Choose sunny, windless days, preferably before 9 AM or after 4 PM.

For effective application:

1. Clean spraying equipment thoroughly before use to avoid contamination and herbicide damage.
2. Ensure the soil is well-prepared with no plant residues to ensure even herbicide distribution.
3. Dilute the herbicide twice. First, mix it with clean, warm water to create a concentrated solution. Then, add room temperature water. Avoid using cold water, as it can reduce effectiveness.
4. On windy days, lower the spray nozzle and use a shield to prevent drift. Avoid spraying in strong winds to ensure the herbicide reaches its target.
5. Ensure the soil is moist. Adequate water helps form a uniform herbicide layer. If the soil is dry, the herbicide won’t penetrate effectively, leading to poor control. Most pre-emergence herbicides work through weed shoots or stems.
6. Apply before rain or irrigation. Rain or irrigation after application can wash away the herbicide, reducing effectiveness. In hot, sunny weather, herbicide can evaporate, decreasing effectiveness.
7. Follow herbicide instructions carefully and avoid over-application.

Proper pre-emergence control will help protect your corn and ensure a successful growing season.