Open it. If it smells fresh, like earth, and not stale, sour, vinegary, bad, or rotten, it's fine to use. I regularly store potting mix for longer periods of time, and I've already purchased my potting mix for next year's flowers (due to the COVID situation, which I expect to be an issue next fall and winter; I stocked up in a massive burst in June to save trips and exposure). There will be absolutely no issues.

Most soils have tiny pinholes in the bags for aeration. Some, however, do not.

If it does smell sour, stale, or nasty, all is still not necessarily lost. Try airing it out, or baking it in the oven (seriously) at 350 for two hours for amounts up to two inches deep and as wide as will fit on any tray or pan (use a thermometer to assure that the center of the pile reached at least 170 for an hour). That will kill disease organisms and their spores--all of them.

Extended exposure to air and sunlight will actually take care of many issues, but caution is called for.

Potting mix doesn't go bad :-) It may become anaerobic if exposed to rainfall or other moisture while still bagged but that is easily remedied by exposing it to air and sunlight. It can develop some fungal issues also while in this state but they are merely saprophytic fungi feeding off of whatever organic matter may be included in the mix and are harmless to plants

I make my own custom mix in large batches and store in lidded plastic totes until needed so it is often overwintered from one growing season to the next. Been doing this for the last 25 years or so and no issues at all.

When compost or bark intended for horticultural use is wind-rowed (piled in wind rows) anaerobic composting will cause organic acids to build in the product unless it's turned (rolled over - remixed) with regularity. The same is true if a medium is stored moist in bags that don't allow it to dry quickly. Allowing the soil to air out, doesn't fix that - it would need to be leached. ....... best to allow it to dry completely before bagging it.

Also, be very careful about storing moist medium you've added a CRF product added to. CRF's release rates are most often driven by temperature, but moisture is also an essential component. Over time, all the fertilizer content from CRF prills can enter the medium and cause EC/TDS levels high enough to cause fertilizer burn.

Al

Al, would you recommend he leach it out by letting it wash through as well, or do you think that would be unnecessary and the issue would be with volatiles?

Any volatile compounds would more likely come under the topic of allelopathy, unless I'm misunderstanding your question.

If moist soils are stored in plastic bags, and/or they have had CRF added, they should be leached thoroughly before planting in them.

Al

How do you leach the medium? Is this excessive top watering or a flood, soak, and drain type procedure?

Either.

Al

If you've ever put something like soil in the oven in your house, you'll probably not do it again. Smells to high heaven.

@User so you're the one who bought it all up! LOL How much TP do you have on hand? :-P

"If you've ever put something like soil in the oven in your house, you'll probably not do it again. Smells to high heaven."

It's not that bad if you follow the baked potato method and limit oven temperature to 350. But I wouldn't exactly call it pleasant if the soil was sodden and had a lot of cyanobacteria and algae in it. I'd rather do the solarization method out on the patio on a tarp.

"@morpheuspa2 so you're the one who bought it all up! LOL How much TP do you have on hand? :-P"

I refuse to answer that to avoid having raiders hit the house. :-) But seriously, when it all goes to crap (figuratively speaking) again in October, I have enough to last through at least April as far as crap is concerned (literally speaking). And I did buy it after the shortages were over and nobody suffered due to my stockpililng.