I've been "stealing" dirt from a local park for my balcony garden. The park is filled with pine trees which, I've come to learn, indicates very acidic soil. Is there any way to improve my soil pH and quality without formal testing?
Compost, if you can find a source for it. Balcony garden sounds like you wouldn't have the space for a tradition compost pile, but I think worm castings are also usually neutral PH. Plus both worm castings and compost are pretty much always a good idea.
A little wood ash from a friend that burns wood might work too. Heck I would send you some by mail if you really wanted it.
I do wonder why you cannot test the soil though? Its like $12 for a full soil report, and if you know someone in a chemistry lab or whatnot, might be able to get a couple of PH paper strips. There is a saying in farming, "It is just a guess unless you test". That applies no matter how big the soil is that you are working.
An old fashion pH test you can do is to just wet the soil down and pour baking soda on it. Usually it will indicate the acidity based on the reaction so just add lime or ash loosely until it no longer reacts. You would be testing these in small combined samples. Also keep in mind you may want to keep it slightly acidic as most plants teeter on a 6.5-7.0 pH.
Wait a sec. Don't assume pine trees automatically mean acidic soil.
I have property where the soil is very alkaline. Scots Pine are one of the pioneer trees moving in. Only after the first generation of them dies off is the soil more towards neutral.
You can use pH paper (litmus paper) or you can go to just about any nursery or big box store that sells plants and find a pH meter for under 30 dollars US, either of these will give you a good enough reading.
It is possible to "eye ball" pH but most likely you will be off just enough for plants to notice.
If you need to increase alkalinity (above 7.0 which is neutral) then you can use crushed up gypsum board usually easy to find where drywall is going up at construction sites, or lots of ground (crushed) sea shell or egg shells but it will take a lot of those two.
Or if you can find it agricultural lime.
If you need to decrease alkalinity (below 7.0) then you can use ground sulfur, or even diluted battery acid (which is sulfuric acid) will work when used very carefully as a water in amendment.