Methylated Seed Oil (MSO) is an agricultural adjuvant added to a spray tank mixture to enhance the performance of crop protection products, typically herbicides or pesticides. MSO is a modified vegetable oil designed to improve the physical properties of the spray solution, ensuring the active chemical works as intended. This article provides practical guidance on calculating the correct amount of MSO to mix per gallon of spray solution.
Understanding MSO’s Function
MSO is utilized primarily for its dual mechanism as a surfactant and a penetrant. The “methylated” modification allows it to mix more readily with water and helps spray droplets spread across the plant surface. This reduction in water droplet surface tension, called wetting, ensures more uniform coverage of the target foliage.
The second key function is penetration, which helps the active ingredient pass through the plant’s waxy outer layer, or cuticle. This outer layer is a protective barrier that normally repels water-based sprays. MSO temporarily alters the structure of this waxy layer, facilitating the chemical’s uptake into the plant tissue. This enhanced absorption is beneficial when applying post-emergence herbicides, especially under environmental stress conditions like low humidity or drought.
Calculating Standard Application Rates
Determining the precise amount of MSO required is based solely on the recommendation provided on the label of the specific crop protection chemical. The label is the only legal and accurate source for the mixing ratio, which depends on the active ingredient, the target plant, and the application conditions.
Typical mixing rates are expressed as a percentage of the total spray volume, usually ranging from 0.5% to 2.0% volume/volume (v/v). For small-batch mixing, this percentage must be converted into fluid ounces. Since one U.S. gallon contains 128 fluid ounces, the calculation involves determining the percentage of 128 ounces.
To convert the percentage rate into ounces per gallon, multiply 128 by the decimal equivalent of the percentage. For example, a 1.0% v/v recommendation translates to \(0.01 \times 128\), resulting in 1.28 fluid ounces of MSO per gallon.
For small area treatments, some MSO labels simplify this by recommending 1 to 2.5 ounces of MSO per gallon of finished spray solution. This guidance provides a practical measure for backpack or handheld sprayers. The higher end of the recommended range is reserved for hard-to-control weeds or when target plants are under stress.
Safe Use and Practical Mixing Procedures
Proper tank mixing procedures are necessary to ensure the chemicals emulsify correctly and remain stable. Begin by filling the spray tank approximately half to three-quarters full with water while starting the agitation mechanism. The active chemical should be added next and allowed to disperse fully.
MSO, as the adjuvant, must always be the last liquid component added to the mixture. After adding the measured amount, continue agitation for a minute or two before adding the remaining water volume. This sequence prevents the MSO from interfering with the initial dispersion of the active ingredient.
Safety precautions must be observed during handling and mixing. Handlers should wear appropriate Personal Protective Equipment (PPE), including chemical-resistant gloves, eye protection, and long-sleeved clothing. Adequate ventilation is necessary to avoid inhaling spray mist or fumes.
Disposal Guidelines
Any unused spray solution containing MSO should be applied to a labeled site or disposed of properly. Empty containers must be triple-rinsed before disposal to prevent environmental contamination.