Nonionic Surfactant for Herbicides: Improving Weed Coverage & Application Performance
Why water surface tension causes herbicide droplets to roll off waxy weed foliage—and how nonionic spray adjuvants like APSA-80® improve leaf wetting and droplet spreading.
Quick Answer
A nonionic surfactant (NIS) is an agricultural spray additive that breaks the surface tension of water without carrying an electrical charge. When added to compatible post-emergent herbicides, it prevents droplets from forming high-standing beads on waxy or hairy weed leaves, allowing the solution to spread into a uniform film for better leaf contact.
In our real-world experience, APSA-80® (80% active ingredient nonionic surfactant) is used at 2.5 to 5 oz per acre with herbicides where the pesticide label specifies or permits a nonionic surfactant.
The Physics of Water Surface Tension & Waxy Weed Leaves
Water molecules are naturally cohesive—they pull tightly together into sphere-like droplets. When plain spray water hits the waxy cuticle or trichomes (leaf hairs) of tough weeds like pigweed, lambsquarter, or Bermuda grass, high surface tension causes the water to form tight beads that bounce or roll off.
Adding a nonionic surfactant like APSA-80® lowers the contact angle between the droplet and the leaf surface.
Instead of sitting high on top of leaf hairs, the liquid flattens, spreading herbicide across a significantly larger surface area.
4 Key Benefits of Adding NIS to Post-Emergent Herbicides
Flattens spray droplets instantly upon impact, helping more spray solution remain on the target weed rather than falling to the soil.
Helps the herbicide active ingredient make intimate contact with leaf stomata and waxy outer cuticle layers.
APSA-80® helps suspend dry flowables (DF) and wettable powders (WP), reducing clogging in boom nozzles and filters.
Formulated to be non-corrosive to pumps, aluminum booms, brass nozzles, and poly spray tanks when used as directed.
Adjuvant Comparison: NIS vs. COC vs. MSO
| Adjuvant Class | Active Components | Best Used When... | Crop Safety Risk |
|---|---|---|---|
| Nonionic Surfactant (NIS) e.g., APSA-80® | Alcohol ethoxylates, nonionic wetting agents (80% active) | Post-emergent systemic & contact herbicides requiring wetting | Lowest risk when label rates are followed |
| Crop Oil Concentrate (COC) | 80-85% petroleum oil + 15-20% emulsifier | Weeds under heavy drought stress or thick wax | Moderate crop burn risk in hot weather |
| Methylated Seed Oil (MSO) | Esterified seed oil + surfactant emulsifier | Heavy waxy leaves or tough perennial species | Highest crop burn potential under hot conditions |
Pro Tip: Always Read the Pesticide Label First
Never add a surfactant blindly. Some herbicide labels state "Do NOT add NIS," while others state "A nonionic surfactant containing at least 80% active ingredient MUST be added." APSA-80® meets the 80% active requirement specified by leading herbicide manufacturers.
Authoritative Herbicide & Surfactant Resources
Related Technical Guides
Frequently Asked Questions
What is a nonionic surfactant, and why is it used with herbicides?
A nonionic surfactant lowers the surface tension of spray water without carrying an electrical charge. When added to herbicides, it prevents spray droplets from beading up on waxy or hairy weed leaves, helping the active herbicide spread evenly across the leaf surface.
Is APSA-80® a nonionic surfactant?
Yes. APSA-80® is a concentrated nonionic surfactant containing 80% active ingredients. It acts as a spreader, wetting agent, and activator for compatible agricultural sprays.
Does every herbicide require a nonionic surfactant?
No. You must always read the specific herbicide label first. Some herbicide formulations already contain built-in surfactant systems or explicitly require a crop oil concentrate (COC) or methylated seed oil (MSO) instead.
What is the typical application rate for APSA-80® with herbicides?
According to the specimen label, the general herbicide application rate is 2.5 to 5 fluid ounces per acre (or per 10 to 40 gallons of spray solution). Always verify exact rates against your herbicide label and current product instructions.
Can adding a surfactant cause crop injury?
If used at rates exceeding label recommendations or during extreme environmental heat/stress, excessive surfactant activity can increase crop uptake beyond intended safety thresholds. Always follow label directions and perform compatibility tests.
Improve Your Herbicide Application Performance
Contact our distributor team for APSA-80® specimen labels, application rates per 100 gallons, and California delivery options.
