Multiple materials in one input log

Requested by Tyrel_88_ in IRC today:

So when I am entering inputs on a field, I have to make a whole new entry for each input. The trouble is that I mix fertilizer, weed spray, and surfactant all in the same tank. This will make it difficult to keep my records straight if I have to enter that I went over the field 4 times when in reality I went over the field once and put down 4 inputs.

I wonder if there is a way to add multiple inputs per entry?