Weed control at the sowing stage is a critical step in ensuring healthy crop growth. One of the commonly used herbicides is Atrazine, which effectively controls a wide range of annual grasses and broadleaf weeds. Its performance against broadleaf weeds is generally better than against grassy weeds. Atrazine can be applied either pre-emergence (before planting) or post-emergence, ideally when corn has 3–4 leaves, and grassy weeds have 1–2 leaves, while broadleaf weeds are at the 3–4 leaf stage. The recommended dosage is 150–200 ml per mu of 40% Atrazine suspension. In soils with high clay content or organic matter, it's advisable to increase the dose for better effectiveness.
However, soil organic matter strongly adsorbs Atrazine. If the organic matter content exceeds 6%, using Atrazine may not be cost-effective due to reduced herbicidal activity. In such cases, it's better to switch to post-emergence foliar application or use alternative herbicides. For post-emergence treatment, 200–270 ml per mu is typically sufficient.
In areas where Atrazine is overused (more than 133 g/mu), it becomes harmful to sensitive crops like wheat, soybeans, and millet. Pre-emergence soil treatments are more effective against grassy weeds, while post-emergence foliar treatments work better on broadleaf weeds. In high-organic-matter soils, foliar applications are most effective. To minimize crop injury, it's important to reduce Atrazine usage as much as possible.
Another effective herbicide is Isobutyl (also known as Dinotefuran or Glycyrrhiza), which controls various annual grasses, broadleaf weeds, and some sedges. It is applied before sowing by spraying the soil. For sandy loam, use 270 ml/mu of 85% EC formulation, and for clay soil, 350 ml/mu. Since Isobutyl is volatile, it must be incorporated into the soil within 20 minutes after application.
Metolachlor (Dole) is also widely used for controlling annual grasses and some broadleaf weeds. It is best applied before or immediately after sowing, with a recommended dose of 100–200 ml/mu of 72% EC. Sandy soils require lower doses, while clay soils and those with high organic matter need higher amounts. In dry conditions, the herbicide should be mixed into the top 2–3 cm of soil.
Alachlor is another option that targets similar weed species. It is applied before or after sowing, with a dosage of 250–400 ml/mu of 48% EC. Again, sandy soils require less, while clay and high-organic-matter soils need more. If the weather is dry, mixing the chemical into the topsoil or irrigating afterward improves its efficacy.
Acetochlor is particularly effective against annual grasses and broadleaf weeds. It is best applied right after sowing, with dosages adjusted based on soil type. In North China, where organic matter is below 6%, 150–200 ml/mu of 50% EC is recommended. For soils above 6% organic matter, increase to 200–270 ml/mu. Applying it to the top 2–3 cm of soil enhances its performance. In dry conditions, irrigation is advised, and covering the field with plastic film can reduce the required dosage by about 30%.
In addition to single herbicides, mixed applications are often used to improve weed control efficiency. Nicosulfuron (Yu Nong-le) is effective against grasses, sedges, and broadleaf weeds, including species like Setaria viridis, Digitaria sanguinalis, Amaranthus retroflexus, and Cyperus rotundus. It is applied as a foliar spray at 100 ml/mu of 4% aqueous solution.
Dicamba is another powerful herbicide for broadleaf weed control. It is applied during the 3–4 leaf stage of corn, with 33–40 ml/mu of 48% water-dispersible agent. When used correctly, it is safe for corn, but improper timing, excessive dosage, or poor application techniques can cause phytotoxicity.
Combining Atrazine with Nicosulfuron (Atrazine + Jade Farm) enhances the herbicidal spectrum and improves control over difficult-to-manage weeds. This combination reduces the amount of Atrazine needed, improving safety for subsequent crops. It is applied during the 2–4 leaf stage of corn seedlings and weeds, with 67 ml/mu of 4% yam agricultural water agent plus 100 ml/mu of 40% Atrazine suspension.
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