What herbicide is used for pre-emergence closed weeding in soybean, and when should it be applied?

SummaryAcetochlor: apply 3-5 days before emergence. Chlorimuron-ethyl: apply 3-5 days before emergence. Metribuzin: carry out soil treatment 3-5 days before emergence. Clomazone: carry out closed weeding after sowing and before emergence. Glyphosate: apply 2-3 days before emergence.

1. Acetochlor

1. Acetochlor (50% acetochlor, 90% acetochlor, 90% Shengnongshi, 90% Henaisi) is generally used as a soil treatment and can be applied 3-5 days after sowing and before emergence.

2. But note that applying it during the soybean seedling soil-cracking stage will cause herbicide injury, especially when mixed with herbicides for controlling broadleaf weeds; applying it during the soybean seedling soil-cracking stage may cause a reduction in yield. The application rate of soil closed weeding herbicides needs to be adjusted according to soil type and organic matter content.

2. Chlorimuron-ethyl

1. Chlorimuron-ethyl (Douhuanglong, Doucaolong) can be used before or after soybean seedling emergence, but use after emergence easily causes herbicide injury, so it is not recommended; it is generally used for soil treatment after soybean sowing and before emergence. After soybean sowing and 3-5 days before emergence, 60-75g of 20% chlorimuron-ethyl can be used per hectare.

2. Chlorimuron-ethyl can effectively control weeds such as cocklebur, Mosla chinensis, velvetleaf, Bedstraw grass, Galeopsis bifida, Polygonum, and Chenopodium, and it has an inhibitory effect on Equisetum arvense, Cirsium japonicum, Polygonum convolvulus, and grass weeds, but its efficacy against chickweed, black nightshade, and Commelina communis is poor.

3. Metribuzin

Metribuzin (Saike, Jiacaozin) can generally be used for soil treatment after soybean sowing and 3-5 days before emergence. Metribuzin can effectively control various broadleaf weeds such as Amaranthus, Chenopodium, Polygonum, chickweed, cocklebur, and Bedstraw grass.

4. Clomazone

1. Clomazone (Guangmieling, Tiandeji, Doucaoling) can be used for closed weeding before soybean sowing or after sowing and before emergence, and can also be used for early post-emergence stem and leaf treatment.

2. It can effectively control annual grass weeds and broadleaf weeds such as foxtail, barnyardgrass, crabgrass, black nightshade, Mosla chinensis, Amethystea caerulea, purslane, velvetleaf, Setaria glauca, wild watermelon seedlings, Chenopodium, Polygonum, cocklebur, and Bedstraw grass, and it also has a certain inhibitory effect on perennial weeds such as small thistle, Cirsium japonicum, Equisetum arvense, and sowthistle.

5. Glyphosate

1. Glyphosate (Nongda, Kelingda, Haolida, Nongminle) can be used on newly reclaimed wasteland and on other plots with many perennial weeds to control early spring weeds.

2. After waiting for the weeds to emerge fully, spray glyphosate 2-3 days before soybean seedling emergence; it can effectively control perennial weeds that have already emerged, and glyphosate has relatively strong systemic translocation action, generally capable of killing the underground parts of plants, thereby reducing damage the following year.