Oil adjuvants can increase the penetration of oil-soluble herbicides into plants, and are commonly used when conditions are hot and dry, and/or when leaf cuticles are thick.
They are derived from either refined petroleum (mineral) oils or from vegetable oils (including seed oils), and do not readily mix with water.
Therefore, when an oil adjuvant is combined with water in a spray tank, a surfactant emulsifier must also be added, which distributes the oil droplets (micelles) uniformly throughout the mix. These “emulsifiable oil” adjuvant combinations typically contain both a non-phytotoxic oil (typically ranging 80 to 99%) and a surfactant (1 to 20%), and are added to the spray tank usually as just 1% of the total spray volume.
Emulsifiable oil adjuvant blends can enhance the absorption of an oil-soluble herbicide into the plant more than an oil adjuvant by itself. Adding a surfactant to the mixture not only emulsifies the oil in the water-based spray solution, but also lowers the surface tension of the spray solution. These adjuvants can also increase herbicide absorption through the plant cuticle, increase spray retention on leaf surfaces, and reduce the time needed for the herbicide formulation to become rainfast.
Two types of emulsifiable oil adjuvants are “crop oils” and “crop oil concentrates” (COC). Crop oils contain up to 5% surfactant and COCs may contain up to 20% surfactant. COCs enhance spreading and penetration and are used primarily with grass-specific herbicides. Crop oils and COCs do not necessarily contain oil derived from crop plants (although some do), but are so named because they are intended for application to crops.
Oil adjuvants are derived from either refined petroleum (mineral) oils or from vegetable oils (including seed oils), and do not readily mix with water.
Petroleum oils or petroleum oil concentrates are highly refined oils, which are often used as carriers of oil-soluble herbicides. They are typically used in low quantities (generally 0.25 to 1 gallon/acre), and when used as carriers, can reduce surface tension, increase wetting and spreading, give quicker absorption, improve rainfastness, and reduce loss of carrier during and after application.
Petroleum oil concentrates may include paraffinic and napthalenic oils.
Vegetable-derived oils (from soybeans, cottonseeds, etc.) also decrease surface tension, but they are not as effective as other surfactants at increasing spreading, sticking, or penetration. Vegetable oils are generally of two types: triglycerides or methylated oils.
Methylated seed oils (MSOs) provide improved leaf cuticle penetration than conventional crop oil concentrates, and are typically used at lower rates crop oil concentrates. They also aid in the reducing evaporation loss. Methylated seed oil is a product of the reaction of a fatty acid (derived from seed oils) with methyl alcohol. MSO adjuvants usually contain emulsifiers/surfactants. Their primary use is with post-emergent herbicides, insecticides and fungicides, especially those with systemic action. They can also be used with Plant Growth Regulators and foliar fertilizers. Premium products contain silicone surfactants.
For more dicussions of Oil Adjuvants, please contact us: info@profirst.cn.
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