How the tank mix is worked out
The job needs spray volume per area × area of spray in total. Divided by the tank capacity, that gives the number of loads: the whole number is the full tanks, the remainder is the last, partial tank.
For a rate per area, a full tank covers tank ÷ spray volume per area, so the product per tank is the rate × that area. For a concentration rate (per 100 L), the product per tank is the rate × the tank volume in hectolitres. The last tank gets the same proportion of its own volume.
Example
A 1 000 L sprayer applying 300 L/ha over 8 ha needs 2 400 L — two full tanks and a last tank of 400 L. A product at 2 kg/ha takes 6.67 kg per full tank (a tank covers 3.33 ha), 2.67 kg in the last tank and 16 kg in all.
Frequently asked questions
Why is the last tank so important?
Filling the last tank like a full one leaves you either with spray to dispose of or with a block sprayed at the wrong rate. Mixing only what the remaining area needs avoids both.
Per hectare or per 100 L — which does my label use?
Many European labels give a concentration (per hL of spray) with a reference water volume; US labels and many others give a rate per area. Use the form your label uses, and respect any maximum per hectare it states.
How do I find my spray volume per area?
Calibrate: measure the output of every nozzle over a minute at working pressure, and the time to cover a known distance at working speed. Volume per area = total output per minute × 600 ÷ (speed in km/h × row width in m) for L/ha.