Does liquid fertilizers have an expiration date?

[Mrs.Green]

Being a bit frugal ( at least in some ways..) I wonder if liquid fertilizers have an expiration date? I was given two different bottles of cacti fertilizer and my guess is that they are probably at least ten years old. I can’t find any expiration date on either of them. That said, I don’t trust expiration dates that much, since ordinary table salt also have an expiration date..

None of them seems to be ideal regarding the NPK ratio, one is 4-3-5 and the other one 3-2-6. Totally useless if they still aren’t expired?

[MikeInOz]

No, they don't expire but if they form precipitates (solid particles that sink to the bottom, sometimes very fine dust, sometimes like grains of sand) I would not use them.
The usual precipitates formed are... Calcium phosphate and calcium sulphate. If there is no Ca in the fertilizer you probably won't see much precipitation and it should be ok - even if it's 100 years old. Sometimes you can increase solubility by using hot water and citric acid.

Oh and I'm assuming they are not organic?

[Steve Johnson]

The usual precipitates formed are... Calcium phosphate and calcium sulphate.

Hi Mike,

I'm working off a gallon jug of Dyna Gro All Pro 7-7-7 I purchased in early 2012, and here's the chemical analysis:



The analysis suggests to me that it's elemental Calcium, not a salt. Is that correct? If not, do you know what the Calcium salt might be? My only concern would be if it's Calcium phosphate or sulfate. I shake the jug thoroughly whenever I dispense the fertilizer, but if there's any precipitation and it look like sand, I might not see it floating around in the liquid.

[Mrs.Green]

No, they don't expire but if they form precipitates (solid particles that sink to the bottom, sometimes very fine dust, sometimes like grains of sand) I would not use them.
The usual precipitates formed are... Calcium phosphate and calcium sulphate. If there is no Ca in the fertilizer you probably won't see much precipitation and it should be ok - even if it's 100 years old. Sometimes you can increase solubility by using hot water and citric acid.

Oh and I'm assuming they are not organic?

Thank you very much MikeInOz I can’t hear anything when shaking the bottles but I will use a flashlight to try to see inside the bottles. No, they are not organic.

[MikeInOz]

The usual precipitates formed are... Calcium phosphate and calcium sulphate.

Hi Mike,

I'm working off a gallon jug of Dyna Gro All Pro 7-7-7 I purchased in early 2012, and here's the chemical analysis:



The analysis suggests to me that it's elemental Calcium, not a salt. Is that correct? If not, do you know what the Calcium salt might be? My only concern would be if it's Calcium phosphate or sulfate. I shake the jug thoroughly whenever I dispense the fertilizer, but if there's any precipitation and it look like sand, I might not see it floating around in the liquid.

Hi Steve
My guess is that the Ca would be added as the calcium nitrate. It's impossible to have just the single element (in this case the cation Ca) without the anion (nitrate, phosphate, sulphate, chloride etc.)
Shake some of the fertilizer then quickly pour some into a clear glass before anything settles. If there are any precipitates you should see them on the bottom after a few seconds. If they are very fine they might look ''cloudy'' and settle very slowly.
Once I wanted some ammonium nitrate but you can't buy it anymore (some people (not me!) like to make bombs), so I made my own by mixing Calcium nitrate with ammonium sulphate in solution and ended up with a solution of ammonium nitrate (more or less) with a sludge of calcium sulphate (gypsum) on the bottom. I still have some but hardly use it anymore. This is what happens when you have sulphates and calcium in the same bottle and that's why hydroponic fertilizers are sold in 2 parts - Calcium nitrate in one and everything else in the other.

[Steve Johnson]

This is what happens when you have sulphates and calcium in the same bottle and that's why hydroponic fertilizers are sold in 2 parts - Calcium nitrate in one and everything else in the other.

Okay, good to know! Per your suggestion, I I just poured out some of the 7-7-7 (shaken, not stirred ) in a clear glass jar. After 10 minutes, there were no precipitates settling down at the bottom, so the fert is still good.

Thanks, Mike!

[greenknight]

Should probably mention that while concentrated fertilizer has no expiration date, once you dilute it with water you need to use it up - don't store any leftover diluted fertilizer, bacteria will grow in it.

[MikeInOz]

(shaken, not stirred )

So you're telling me you found no ''Bonds" ?

[Steve Johnson]

So you're telling me you found no ''Bonds" ?

No "Bonds", 007-7-7.