How long after applying corn herbicide must it be before rain is safe?
Many farmers do not check the weather forecast when spraying corn herbicide, and then it rains right after spraying. So how long after applying corn herbicide must it be before rain causes no harm?
1. How long after applying corn herbicide must it be before rain causes no harm
It depends on when the rain falls, that is, how long after applying the post-emergence herbicide the rain comes. If the interval is more than 6 hours, there is no need to re-spray, because the weeds have already absorbed the herbicide solution. For example, if you spray in the afternoon and it starts raining at night, there is basically no effect. If you finish spraying in the morning and it starts raining just after noon, or if a sudden shower comes right after spraying, then in that case, move on to the next judgment.
It depends on the amount and duration of the rain, that is, whether it is heavy rain, torrential rain, light rain or drizzly rain. If it is light rain or drizzly rain and it does not last long, the effect is not great. On the contrary, if it is heavy rain or torrential rain and it lasts a long time, then you need to consider whether to re-spray.
2. Types of corn herbicide
1. Amide herbicides: This type of product is currently the most important class of herbicide for cornfields. It can be absorbed by weed buds and used for soil-closing treatment before weeds sprout, and can effectively control annual grass weeds and some annual broadleaf weeds. There are many varieties in this class of herbicide, such as acetochlor, alachlor, butachlor, metolachlor, propisochlor and so on.
2. Triazine herbicides: They can effectively control annual broadleaf weeds and annual grass weeds, mainly absorbed by weed roots, and can also be absorbed in small amounts by weed stems and leaves. Representative varieties include atrazine, cyanazine, simazine, prometryn and so on. Among them, atrazine is used more widely, is relatively safe for corn and has the highest activity; but atrazine should preferably be mixed with acetochlor and the like to reduce the dosage and improve the weeding effect and the safety of subsequent crops.
3. Phenoxycarboxylic acid herbicides: They are mainly used after corn emergence to control broadleaf weeds and purple nutsedge. Representative varieties include MCPA-sodium salt and 2,4-D butyl ester. Among them, MCPA-sodium salt is widely used in cornfields to control purple nutsedge, but improper timing of use can easily cause phytotoxicity.
4. Sulfonylurea herbicides: Nicosulfuron and rimsulfuron can be used in cornfields to control grass weeds, sedge weeds and some broadleaf weeds; thifensulfuron can be used in cornfields to control annual broadleaf weeds.
5. Other herbicides: Paraquat and glyphosate are non-selective herbicides and can be used for directed spraying after corn reaches 40 cm in height, effectively controlling many kinds of weeds; fluroxypyr, dicamba, bromoxynil, bentazone and other varieties can also be used to control broadleaf weeds in cornfields.
Corn herbicides are rich and varied. If you choose the right type of chemical and use it scientifically and reasonably, and pay attention to the weather forecast before spraying, you can achieve relatively good results.