Does fertiliser have a use by date, and is it essential to follow it?

[Philthy]

Just that really. And specifically relating to Fish, Blood and Bone. I have half a tub of the stuff, probably 7 years old. Can I still use it / will it still work?

Many thanks

[Glutton4...]

I'd still use it. In my cynical opinion, sell/use by dates are there to encourage us to chuck out, and buy more. It's all about money.

[shepp726]

if you want to go by use by dates, any out of date ones could be watered around shrubs, hedges, trees, am sure they'll appreciate it.

[rustylady]

If it's been stored in the tub, cool and dry, it will be fine.

[snohare]

If it looks the same as it did when the box was first opened, then there will not be much change chemically. Not a golden rule, but true when it comes to fertiliser. Rustylady is bang on. I have used stuff that is years old, never noticed a difference; but once wetted, you will lose minerals etc by leaching. (That's why you have to add to the soil in the first place - leaching from the soil into the water table.)