The following is the effective period classification and key information of different types of herbicides:
1. Short-acting herbicides (effective period ≤ 7 days)
Cyhalofop-butyl: The half-life of degradation in soil is <4 hours, non-toxic to fish.
Dipyridamole: The half-life in rice plants and soil is only 1.2-1.3 days.
High-efficiency fluazifop-butyl: The half-life is about 20 hours, suitable for rapid rotation after grass weeds.
Quizalofop-butyl: The half-life is <1 day, mainly decomposed by microorganisms.
2. Medium-acting herbicides (effective period 7 days-6 months)
Ethylpyrachlor: The effective period is 8-10 weeks, often used for soil sealing before sowing.
Isopropylamine: The half-life is 10-26 days (depending on the region), and the effective period is 8-12 weeks.
Pendimethoate: Residual period 6-9 weeks, half-life 14.7-19.5 days.
Fomesafen: Half-life 3 weeks in irrigated soil, up to 6-12 months under drought conditions.
3. Long-acting herbicides (lasting effect > 6 months)
Cycloazine: Lasting effect 2-3 years, used in non-cultivated land such as forest land and barren hills, strong systemic.
Methiosulfuron-methyl: Residual 12-24 months, strictly prohibited for use in farmland.
Isopropylamine: Lasting effect at least 6 months, rotation interval 9-16 months (depending on the crop).
Atrazine: Residual effect half a year, corn fields need to be planted with sensitive crops 24 months apart.
4. Key factors affecting the lasting effect period
Environmental conditions: For example, glyphosate degrades quickly in moist soil (a few days to a few weeks), which can be extended to several months under drought.
Soil type: Fluazifop-butyl degrades quickly in yellow soil (11 hours) and more slowly in red soil.
pH value: The half-life of clodinafop-butyl is 2.2 hours at pH = 9 and 64 hours at pH = 7.
