Some products list a rate per volume of water or % volume:volume rather than a rate per ha. How do you calculate how much product to use?
The bicarbonate products (Milstop and Sirocco) are an example of the former. The label states for grapes use 2.8 kg/500 L or 5.6 kg/1000 L water. But what do you do if you’re using 750 L of water? Simply divide the kg by 500 and multiply by the target volume you want to use.
E.g. target volume is 750 L per ha
2.8 kg / 500 L x 750 L = 4.2 kg
Here’s a table to show the different amounts of Milstop/Sirocco for different volumes of water per ha:
With % volume:volume, it’s important to remember to add 2 decimal places to the amount or you may over-dose and run into issues with phytotoxicity. Most of the oil products we have in fruit have this type of rate as do many of the surfactants. If the rate is, for example, for a surfactant at 0.2% volume:volume, mixing a 500 L tank, the volume of surfactant would be 0.002 x 500 L = 1 L.