Fertilizer Expiration?

[MT-Phal]

Hey all,

Does fertilizer expire? I bought some MSU RO, the hard grainy kind that dissolves in water, two years ago. I've noticed that over time it started to harden and lose it's color. It was originally very sky blue, now is lighter and there's some browning within the bag. I've also noticed that once mixed the solution is clear where it was once light blue.

The bag has always stayed sealed when not in use and squeezed to remove any excess air, while stored in a cool and dry cabinet. Still safe to use or should I chuck it?

Thanks.

[voyager]

OK, I'll take a stab at this one.

As a general rule most fertilizers are mineral in form.
Some may be organic, like kelp fertilizers and such.
Again as a general rule, crystalline fertilizers are inorganic mineral compounds.
By everything reasonable, they should not be subject to degradation, if stored properly [cool, dry and protected from moisture].
Pretty colors are often added as marketing incentives and make no difference.

I am still using fertilizers I bought in 50# bags 5 years ago.
They seem to be doing their job and doing no harm to our fruit trees.
Orchids are tough and frugal. It takes a lot to kill one and they survive on very small quantities of nutrients.
With that said, I still kill one every once in a while with my ham fisted methods, more often through neglect.

[MT-Phal]

Originally Posted by voyager

OK, I'll take a stab at this one.

As a general rule most fertilizers are mineral in form.
Some may be organic, like kelp fertilizers and such.
Again as a general rule, crystalline fertilizers are inorganic mineral compounds.
By everything reasonable, they should not be subject to degradation, if stored properly [cool, dry and protected from moisture].
Pretty colors are often added as marketing incentives and make no difference.

I am still using fertilizers I bought in 50# bags 5 years ago.
They seem to be doing their job and doing no harm to our fruit trees.
Orchids are tough and frugal. It takes a lot to kill one and they survive on very small quantities of nutrients.
With that said, I still kill one every once in a while with my ham fisted methods, more often through neglect.

Great, thanks. I'm wondering if there was moisture already in the bag when I got it and has since gone moldy. My one and only orchid is now around thirteen years old so I certainly would like to avoid killing it via bad fertilizer at this point.

[voyager]

Most of the crystalline fertilizers are also hygroscopic.
The fertilizers I bought for our fruit trees have turned into large blocks of an astringent green and white speckled material.
I have to take a hand cultivator, a hammer and a piece of 1/4" hardware cloth to get it small enough to run through my small battery powered hand spreader.
Fertilizing our fruit trees is a lot of work.
Living in a humid climate has its drawbacks.

[Ray]

There is no issue with the fertilizer.

The color is not to make it "pretty", it is an indicator so that you know that you're dealing with fertilizer solution instead of plain water, which is how the solution would appear without the dye.

The dyes are pH sensitive - if your hands turn blue, use ammonia to wash it away.

As voyager said, the fertilizers are highly hygroscopic, so the first time you opened the bag, enough moisture was absorbed to cause the pH shift, affecting the color.