Mix together? Generally no. Negates the benefits of each in many cases plus possible chemical interactions.

Alternate them? Sure, per label directions on timing.

A simple calendar with dates and names solves one problem and using separate, labeled sprayers for each chemical is always recommended anyway.

Dave

Separate sprayers for each? That's a lot of sprayers....I don't really have a lot of room for storage...they're pretty big (about a gallon each). Is it ok to rinse out the sprayer and hose, and just alternate the solution as needed?
Don

s it ok to rinse out the sprayer and hose, and just alternate the solution as needed?

Yeah, with great care since many of them contain emulsifiers and oils so a quick rinse and dump with cold water doesn't cut it,

But just ask the gardener who didn't get it rinsed well and ended up spraying herbicide along with the fertilizer if having only one sprayer is enough.

At the very least separate marked sprayers for fertilizers, pesticides, herbicides, and fungicides to avoid cross contamination can prevent a lot of grief.

Switch to hose-end sprayers. They are small, easy to store, and cheap.

Dave

go to three sprayers, one for weed killer, one for fungicide and one for pest killers. You can use either of the ones that aren't weed killer for fertilizer. But don't use the weed killer one for anything but weeds!