Surfactant Adjuvant & Make the Spray Spread & Stick

A surfactant (or adjuvant) lowers the surface tension of spray droplets so the liquid spreads out and sticks on the leaf rather than beading up and rolling off. On waxy or hairy leaves that otherwise shed spray, it dramatically improves coverage and the uptake of the active ingredient, making the same dose of pesticide work better.

The dose is a small percentage by volume (% v/v) of the spray solution. Surfactant per tank = tank volume × (% v/v ÷ 100). For example a 1% v/v rate in a 200 L tank needs 2 L of surfactant; a 0.1% rate needs 200 mL. This tool gives the surfactant per tank, total mL, total litres and the number of tanks for your whole spray volume.

Percent volume per volume is the share of the final spray mixture made up of the adjuvant. A 0.25% v/v rate means 0.25 L of surfactant in every 100 L of spray — that is 250 mL per 100 L, or 2.5 mL per litre. Always mix as a percent of the spray volume, not of the product being sprayed.

Many weeds and crops have a waxy cuticle or hairy surface that repels water, so plain spray droplets bead up and fall off, wasting product. A surfactant breaks that surface tension so the droplet flattens, wets the leaf and holds on long enough for the active ingredient to be absorbed — exactly where you need coverage most.

Follow the pesticide and adjuvant labels — typical non-ionic surfactant rates are 0.1–1% v/v depending on the product and target. Too little gives poor wetting; too much can cause excessive run-off or even leaf scorch. When the label gives a rate per 100 L, convert it to % v/v and enter it here.

No. Up to the labelled rate, surfactant improves wetting and spread, but beyond it the extra simply runs off the leaf, can foam in the tank, and may damage sensitive foliage. The goal is even coverage to the point of run-off, not dripping — so stick to the recommended % v/v.

Generally add the surfactant near the end of the mixing sequence, after the pesticide is in and dispersed and with the agitator running, then top up with water — but always follow the product's mixing order. Adding it too early or to a near-empty tank can cause foaming. Spray promptly once mixed.

Yes — enter your tank size and total spray volume in litres and the % v/v rate, and it gives the surfactant per tank plus the total surfactant and number of tank loads for the whole job. It works for knapsack, boom or any sprayer as long as the rate is expressed as % v/v.

The arithmetic is exact for the % v/v you enter. Real-world results still depend on water quality, droplet size, leaf type and spray timing. Use clean, conditioned water, keep the agitator running, and calibrate your sprayer — the calculator handles the dose, good spraying practice handles the rest.