In the cultivation of traditional Chinese medicinal materials, weed growth and quality can significantly impact both the yield and the potency of the herbs. Manual weeding is not only labor-intensive and time-consuming but also difficult to perform consistently, leading to potential damage to the medicinal plants. Currently, there are limited herbicides that are widely used in the large-scale production of medicinal herbs, with most still under experimental development. Based on practical experience, this article recommends three key stages for herbicide application: before sowing, after sowing but before emergence, and after emergence.
Weed control before sowing is considered the most critical period. Farmers should aim for a single, effective treatment to ensure that weeds do not interfere with the herbs throughout their entire growth cycle. Recommended herbicides include 48% Trifluralin and 50% Acetochlor. Trifluralin is effective against annual grassy weeds like crabgrass and goosegrass, as well as small-seeded broadleaf weeds. It remains active in the soil for 2–3 months. Apply 80–100 ml of 48% Trifluralin EC per acre mixed with 40–50 kg of water, spraying it evenly over the soil surface 5–10 days before sowing. Immediately after application, the soil should be lightly tilled to a depth of 5–7 cm.
Acetochlor, on the other hand, inhibits weed germination and root development, and is particularly effective against various annual grasses. It can also suppress some small-seeded broadleaf weeds. Apply 70–75 ml of 50% Acetochlor per acre, diluted in 40–60 kg of water, and spray it onto the soil surface either before sowing or 3–5 days prior to transplanting. However, it should not be used on certain medicinal herbs due to potential phytotoxicity.
After sowing, but before the emergence of the medicinal plants, 20% Paraquat (Traceless Water) and 41% Glyphosate (Roundup) can be applied. These are suitable for crops such as Bupleurum and Radix Saposhnikoviae, which take 10–30 days to emerge. Use 150–250 ml of 20% Paraquat or 150–200 ml of 41% Glyphosate per mu, mixed with 25–30 kg of water. Spray only when weeds are visible, and avoid using these herbicides once the medicinal plants have emerged, as they may harm young seedlings.
For post-emergence weed control, 6% Kecaoxing EC and 8% High-Efficient Straw are recommended. Kecaoxing is effective against both annual and perennial weeds, including broadleaf species. Apply 70–80 ml of 6% Kecaoxing EC per mu, mixed with 30–40 kg of water, and spray when weeds are about 5 cm tall. The 8% High-Efficient Straw is long-lasting and broad-spectrum, controlling grassy weeds like goosegrass, crabgrass, and perennial species like Imperata. Use 25–30 ml per acre, mixed with 20–30 kg of water, and apply during the 3–6 leaf stage of weeds using a fan nozzle to cover both stems and leaves. Note that this product is safe for broad-leaved herbs like Astragalus but harmful to grassy medicinal plants such as alfalfa.
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