My raised beds/containers are surrounded by crushed rock some with some without fabric under it. Looking for a concoction to keep the weeds that pop through under control. Dont want to use a chemical like roundup. Thinking a vinegar,soap,salt mixture in a pump sprayer? Weed burner? Any other secret sauce suggestions? This would be applied to patches of weeds in the rock, not large expanses like a lawn. Thanks!!
If it seems to you that a weed burner would be feasible, it's probably more likely to work than any concoction. Long term you probably will end up wanting to put down fabric.
Acetic acid does work, but ordinary vinegar isn't strong enough. you need to get 20% acetic acid and apply it at a rate of around 1 gallon for 500 s.f. (100 gal/acre). It works better on broad-leafs than grasses, but at that application rate it does work on both. It's best to apply it when it's dry and hot for two reasons. One is that it's primary mechanism is desiccation, and the other is that you want to get it to the roots in concentrated form. If the soil is too wet, it's diluted by the time it reaches the lowest roots. If your soil is damp, you could probably apply at twice the specified rate. (2 gal/500 sf), but I haven't read that. Just my gut feeling.
No need to add soap unless you are adding an oil to your concoction. Most research has shown the oil to not be a useful adjunct.
20% acetic acid won't burn your skin, but will irritate it if you have prolonged contact. It's not a super strong acid, but it's strong enough that you should use PPE (gloves, goggles) and while adding water to 20% acetic acid won't cause a bad reaction, you are moving beyond food grade stuff and should start practicing safe handling, which means that you never add water to acid in order to dilute, instead you add the acid to water. But, in this case, you won't be diluting. If you find anything like 50% acetic acid, be very careful of it. Don't breathe the fumes, etc...
I would be a little bit concerned that you end up generally acidifying your soil. Many of your vegetables have roots that go 2 feet deep, and virtually all your vegetables have roots that are at least 12 inches deep. And, during dry weather, water is drawn up from moist soil below the bottom of the roots, so soil pH matters 3 feet below the surface. So... as a one time weed killer on your paths, acetic acid will work, but you probably want to simultaneously add lime to your beds, and if you till your soil, you will want to get that lime as deep as you can get it.
It's hard to find 20% acetic acid. It's only available as a regulated pesticide. You can't ship it to Alaska easily, and you won't find it at the big box stores. I haven't seen it at Alaska Mill and Feed, but you might start calling a place like that. They certainly can get it on one of their trucks that come up.