Does Fertilizer Go Bad (& a couple other ?s)

[Roberta]

Ah, the wonders of the arcane systems of measurements in the US... Conversions pretty much just make sense for water, where 1 ml of water at 4 deg C weights 1 gram. The volume conversions are not precise, but useful for practical purposes - 1 teaspoon = about 5 ml. So a teaspoon of water would weight about 5 grams. Obviously if one uses these for weight measurements, it depends on the specific gravity of what is being measured.

A "standard" cup is 8 fluid ounces. 1 fluid ounce = 29.5735 ml. 2 cups = 1 pint = 16 fluid ounces = weight would be 473 grams... 1 pound is 454 grams. Hence the mnemonic "A pint's a pound the world around" 4 cups = 1 quart, which is .95 liter. Now, those are US measurments. The British empire used Imperial measures until it became sane and went metric... an Imperial quart = 1.2 US quarts. So it's quite insane... the metric system is based on physical measurements... 1g = 1 ml = 1 cubic centimeter of water at 4 deg C. (So there's a straightforward relationship between units of weight, volume, and linear distance) I'd be delighted if the US went metric... would take a bit of resetting of perceptions (mental conversions and such), but it would make soooo much more sense in the long run.

Back to the original topic, I suspect that orchids don't particularly care whether they get 25 parts per million nitrogen or 20 or 30. So the approximate concentrations that one may get using an imprecise volume is quite good enough... there are other factors ( how much fertilizer is applied, how much stays in the pot as opposed to running out, how often one applies it... once a week or once or every two weeks or whenever one gets around to it) that make more of a difference.

[Ray]

But...

Unit per unit between US & UK is the same - US teaspoon/gallon is equal to the Imperial equivalents.

[SouthPark]

1 U.S. teaspoon is approx 5 mL, while 1 imperial teaspoon is approx 6 mL. And 1 metric teaspoon is approx 5 mL.

So the metric teaspoon is the same as the U.S. teaspoon. The imperial teaspoon is different.

[Roberta]

Originally Posted by Ray

But...

Unit per unit between US & UK is the same - US teaspoon/gallon is equal to the Imperial equivalents.

Something's gotta give... for that to work the Imperial teaspoon has to be bigger than the US teaspoon. Clearly these functional tools are internally consistent but not consistent between types. As far as I know there are no US or Imperial standards on par with the standard kilogram or standard meter (or now, the atomic standards that are even more precise for distance) that are agreed upon throughout the scientific world. The other systems are just conversion factors relative to the metric standards.

[Ray]

The ratios are identical.

[Orchid Whisperer]

To the original question:

Fertilizer going "bad"? Probably not.

However, fertilizer is a mix of chemicals. I think it is reasonable to assume some changes in the chemistry over time, especially the forms of nitrogen that may be present. For example, if the fertilizer lists certain percentages of urea, nitrate, and ammoniacal nitrogen, that "fresh" formulation is likely to change over time (years) as some nitrogen volatilizes, or transforms to a different form.

The fertilizer is still a useful fertilizer, even if it is several years old. If you have a strong preference for the blend to be close to the 'as purchased' formulation, just use the old fertilizer on something else, and buy some new orchid fertilizer.

[Chani]

I'm going to rejuvenate this thread if you all don't mind. I have a similar issue with my current fertilizer practically solidifying because of exposure to air/water. I would like to try the MSU fertilizer and because I live in NYC and my tap water is very clean and doesn't have a lot of dissolved minerals in it, I am going to assume I should use the 'Pure Water' version.

Since I have been reading up on all the calculations and honestly, I now have a massive headache, can you please help me make a liquid concentrate? Here are the relevant details:

Suppose I buy the 1lb size of MSU
Which is 13-3-15
I would like to use the entire pound in the concentrate
In my watering can which is 144 oz
I grow my orchids in various repotme mixes
I water about 1 time per week
And would like the volume of concentrate for me to dilute down in my 144oz can to be easily measured (teaspoon, tablespoon etc.)

Given all that, how much of the liquid concentrate should I measure out at each watering?

And please, no calculations, no directing me to a calculator, just a simple directive.

If the answer is no, there is no easy measure to measure it out, but if you use 3lb of msu instead of 1lb, there will be an easy measure, please tell me.

Thank you all in advance 😊

[WaterWitchin]

Chani, you sound just like me! Fortunately, there are nice folks here who can help... just not me.

Oh Bill??? YooHoo! Are you there?

[Ray]

The MSU RO or K-Lite formulas would be great for NYC water. Here's my recommendation:

1. Add 1 pound of fertilizer powder to your 144 ounce watering jug.
2. Fill with hot water and stir well.
3. Place the concentrate in a sealable glass or plastic container.
4. Add 1 ounce (2 tablespoons) of that concentrate to your watering jug and fill it up with water.

You now have a jug of approximately 100 ppm N solution to apply weekly.

Here's how I got there:

For once-a-week feeding, something in the neighborhood of 75-100 ppm N is a decent level. As the nitrogen content of the two formulas are quite similar (K-Lite is an updated derivative of MSURO), that level of solution requires 2.89g powder/gallon.

As your watering jug is 144 ounces - 1.125 gallons - each jug will need 1.125 x 2.89 g = 3.25 g of powder. So what we need to do is set the dosage of concentrate you want - for the sake of argument, let's make it one ounce (2 tablespoons).

In order to use a pound of powder (454 g) to create a concentrate that gives you a ~100 ppm N solution when one ounce is added to your 144 oz jug, you may mix that full pound of powder with 454/3.25=140 ounces of water.

Considering how close that is you your watering jug, I'd just dump the one pound of fertilizer into your watering jug, fill it to the 144 oz mark with water, mix it and pour it into your concentrate storage container. Shake it well before dispensing one ounce back into your watering jug, fil it up again, and you're ready to go!

[Mountaineer370]

As the person who started this thread, in case anyone is interested, I did go ahead and buy more of the MSU fertilizer. I followed estacion seca's advice and I'm keeping it in the freezer. It's only been a couple months, and it's fine so far, but for me, the 8 ounce size will probably last at least a year.

I also decided, based on the mathematical equations and scientific advice that I was able to process here (which was not all of it, believe me, lol), to use 1/2 teaspoon of fertilizer per gallon of water. My watering cans are two quarts, so I use 1/4 teaspoon per can. They get fertilized twice a month, maybe a little more now since I'm trying to be more aware of it.

To Chani, I think that the post Ray made just above mine is very well-explained and should be easy to follow. Good luck!