How do you know what surfactant and wetting agent formulations can do? Lab tests show what characteristics a formulation has and how they affect tank mix properties.
Draves Test is an in-lab test that can compare how well products can wet hydrophobic surfaces and penetrate hydrophobic solids. The Draves Test is one of many tests run in the Exacto Lab to better understand the properties of our formulations and create better products.
Understanding what goes on in the lab can help users understand how the products they use may act and perform. This helps applicators optimize their tank mixes to achieve ideal results.
*Skein: a length of thread or yarn, loosely coiled and knotted.
Draves Test allows surfactants and other adjuvant products to showcase their “wetting” abilities in comparison to other substances. Wetting refers to the ability of a liquid to coat a solid surface. This capability is essential to optimize plant uptake, ensuring application effectiveness, and minimizing spray runoff. Increasing the wetting capabilities of an application is what surfactants and wetting agents are meant to do.
The cotton skein in this experiment models the plant, showing just how much wetting the adjuvant solution can cause. The more waterlogged the skein becomes in a shorter amount of time, the better the wetting characteristics of the substance. Cotton is mainly composed of hydrophilic cellulose, so it should get wet very quickly. However, a small amount of hydrophobic oils and waxes in the cotton prevent the water from penetrating and adsorbing* to the cellulose. Therefore, the skein will only fall if a surfactant or wetting agent is in the solution.
*Adsorb: (of a solid) hold (molecules of a gas or liquid or solute) as a thin film on the outside surface or on internal surfaces within the material.
A cotton skein cut through the middle to create many equal-length cotton strands
Hydrophobicity is a common trait found in nature and often presents a real challenge. Waxy plant leaves cause water to bead up and roll off the leaf. The same issue can also be caused by microstructures like tiny hairs or ridges on leaves creating a rough surface and, in turn, hydrophobicity. This poses a challenge for water-based herbicides to get inside the plant to do their job. Products like fungicides only protect areas that are covered by the fungicide. So improper wetting causes unprotected patches on the leaf. Some products need to dry to function, and droplets dry slower than a thin layer of liquid does.
While many tank mixes can benefit from the extra wetting power of a surfactant, it is most important for water-based sprays. Since water has a tendency to bead up and roll off waxy plant leaves, water-based sprays typically experience hydrophobic interaction when applied. Adding an adjuvant with surfactant qualities can mitigate this common issue.
In addition to plant leaves, soils can also be hydrophobic. This occurs when sandy soils dry out and when there are high amounts of non-polar organic matter present. Draves Tests can be applicable to soil hydrophobicity but the most common test to measure soil hydrophobicity is called the Water Drop Penetration Time test. Hydrophobic soils are extremely difficult to wet, and this presents problems in both the turf & ornamental and agriculture industries, where soil water retention is essential to maintain high-quality turf or crops. Soil wetting agents are designed to overcome this hydrophobicity and help irrigation penetrate and get into the soil where it is available for plants.
Draves Test doesn’t measure a fundamental force or chemical property. Instead, it is an empirical test that can compare products and solutions consistently and repeatedly. That’s why it is one of several tests used to compare Exacto’s products. However, while a Draves test produces consistent results, like many other tests, some variables cannot be controlled and cause a variance, particularly when the test is performed with smaller solution amounts.
In most situations, Draves produces results that are consistent enough to be statistically significant. Most solutions with test times greater than 60 seconds will show variance in time of less than +/- 10%. Solutions with times less than 60 seconds can sometimes show more variance, but it is usually around 10% of the average time. Variance in the measurements can be caused by skein variability, human variability in cutting and flaying the skein, differences in the solution from test to test, and Critical Micelle Content (CMC) of the test solution.
Critical Micelle Content (CMC) is the concentration of a surfactant in a bulk phase, above which aggregates of surfactant molecules (micelles) start to form.
Draves Tests are an important tool for comparing adjuvant properties. Contact angle and surface tension are other useful tests which provide concrete data on fundamental aspects of a solution, but they do not always correlate to a solution’s ability to wet a surface. Wetting of solid surfaces is a complicated process that depends on a multitude of other factors, and the Draves Test is a useful way to evaluate how adjuvants help accomplish this goal.
Exacto products are developed through rigorous testing that ensures end-users are getting consistent, quality performance. The Draves Test is one useful tool to compare wetting properties of adjuvants. These results, combined with a suite of other tests like contact angle and surface tension, ultimately lead to the development of optimized products that are designed to make a positive impact on spray applications.
Pre-emergence herbicide applications offer a valuable tool to prevent or reduce weed infestations early in the season. While these applications are helpful, it can be a challenge to achieve optimum results. Adjuvant use is increasing and studies continue to prove their effectiveness.
With a dry spring hanging over the corn belt, concerns of returned crop stress remain going into the second half of the season. Regional drought monitor maps give reason for this concern as drought lingers in across much of the central US.
Turf needs water to survive. If not managed effectively, soil moisture can cause consistent problems such as water-repellancy that create dry patches, inconsistent turf appearance, and in severe cases, complete loss of turf. Turf wetting agents help move water into the soil, improve uniformity, and increase moisture retention.
Soil water management plays a big role in both agriculture and turf industries, but turf holds secrets to advancements in moisture management technology that haven’t reached agriculture yet. Agricultural wetting agents are here and ready to help farmers manage water and keep moisture in the soil.
As the heat of summer nears, so does the threat of fungal diseases infecting turf. Planning a fungicide application with adjuvants based on environmental conditions and the turf ecosystem can improve fungicide effectiveness.
Fungicides are an important part of plant health, protecting crops from disease. Corn tar spot, southern corn rust, and frogeye leaf spot are a few diseases that can be costly if not treated with an effective fungicide application. Planning an application with adjuvants specifically targeting these diseases is imperative to reducing disease pressure.
How do great ideas turn into high-quality products? The idea is translated into a stable, quality formulation then the questions begin. At what rate should the product be applied? When should it be reapplied? Can it be mixed with other materials? Does it need to be watered-in? We answer these questions by conducting field trials to put new product ideas to the test under real-world conditions.
Adjuvant decisions may not seem like a big deal, but they can make a real difference in active performance, agronomic effects, and overall cost of an application. It’s important to ask questions to understand product composition and potential agronomic effects to determine if an adjuvant will truly be cost effective.
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