[Sue]

We just bought the old family farmhouse from a cousin who inherited it. Cleaning out some of old Aunt's stuff I came across 2 little bottles of Potassium Nitrate. Guess it was used as a diuretic at one time. Pharmacy bottles are old maybe late 1970's for the youngest possible date. I vaguely remember the pharmacy when I first moved here.

Stuff still useful for fertilizer? Been sealed and in a dark closet. Still little salt looking crystals in clumps.

 

[Sir_BlackhOle]

I'd chunk it and get some Greenlight Stump Remover. Its real cheap and it will be fresh.

 

[Corigan]

Stuff still useful for fertilizer? Been sealed and in a dark closet. Still little salt looking crystals in clumps.

I guess there is always one way to find out, mix up a small solution and dose a bucket of water and see if it rises to the proper nitrate levels on a test kit. If it does I would say it's still good.. Maybe others can chime in with some exact advice that ferts go bad over time, but I have never had a problem with ferts going bad over time.

Matt