The benefits of foliar sprays are well established, but they are only as effective as the leaf coverage they achieve. This is because they rely on absorption through the leaf surface. Covering more leaf surface area means more of the treatment will be absorbed, but to maximize availability to the plant, challenges such as surface tension must be overcome.
What is surface tension?
Surface tension is a property of fluids, where they behave almost as if they have a tiny elastic film on their surfaces pulling them to the smallest possible surface area. For an individual droplet of water, this would be a sphere.
Most people are familiar with this behavior, having seen water droplets “bead up” on a window. You may also have seen water bugs taking advantage of surface tension to walk on the surface of water that they would otherwise sink into.
Surface tension can also be affected when the liquid is resting on another surface. A car windshield, for example, may receive a treatment causing the water to bead and run off. The waxy surface of many leaves has a similar effect. Normally this coating is designed to protect the plant from potential diseases, but it also hinders the entry of foliar fertilizers.
What are surfactants?
Surfactants are compounds used to lower the surface tension of a fluid, typically mixed into the fluid and allowing it to “spread out” further over the leaf surface. In crop production, these are sometimes also known as wetting agents.
The surface tension of water causes droplets of spray to bead on the leaf surface, reducing coverage and limiting absorption. This leads to wasted spray.
Surfactants lower the surface tension of the liquid, causing the droplet to collapse across a larger leaf area for greatly improved coverage and spray efficiency.
Native to the deserts of the American southwest and Mexico, the Mojave yucca, Yucca schidigera, is well known for its high content of steroidal saponins. These are special plant chemicals that act as natural surfactants, even at very low concentrations and account for around 10% of the dry weight of yucca.
Yucca extract is available as a powder or liquid and is widely used in the food, cosmetics, pharmaceutical and agriculture industries. The US Food and Drug Administration has approved it as a food additive with the GRAS label (Generally Recognized As Safe).
Yucca extract used as a seed treatment has been found to improve seed quality and plant growth. These biological effects of saponins are normally ascribed to how they interact with cell membranes. Yucca bark also contains substantial amounts of phenolic compounds.
Alltech processes Yucca extract for agricultural purposes through its plant in Serdán, Mexico. In addition to job creation and boosting the local economy, these yucca operations have received numerous awards for sustainability from the governing authorities. Alltech also provides computers, classroom furniture and facility upgrades for the local primary school as well as a nearby school for disabled children.
Alltech’s sustainable yucca extract production has three important components:
- Sustainable cultivation
It takes around 15 years to grow Yucca for harvest. Alltech follows an environmentally friendly harvest process that is monitored and approved by the Mexican authorities.
- Select potential harvest are
- Conduct environmental impact studies.
- Obtain harvest permits.
- Reforest area at a 2:1 ratio.
The raw yucca logs are processed and pressed through various methods to extract and concentrate the juice in a form that is standardized for consistent quality.
- Finished product
The yucca extract is ready for a variety of applications as either a dry powder or a concentrated liquid extract.
Natural crop nutrition
Incorporating these saponins, natural surfactants, into products allows Alltech Crop Science to produce natural-based products with high efficiency and efficacy, leading to superior crop performance. Less waste means greater environmental sustainability, but also greater business sustainability and profitability for the grower.