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

Apologies in advance for more fertilizer questions. I have searched the forum to the best of my ability but I have not been able to find answers to these particular ones.

My orchid collection is small, only twenty-some plants. I have been using the MSU formula, but I find that even when I buy a small container, by the time I get around to using it up (maybe a year or more?), it has changed color and is stuck together in clumps. It does have the moisture-absorbing packet in it.

My first question is: Does fertilizer go bad after a time, or become less potent? Is what I have described an indication that the fertilizer has degraded in some way?

Second question: I have heard and read many times that we should only be using 1/4 or so of the recommended amount of fertilizer. For clarification, does this apply even when using fertilizer specifically formulated for orchids? Or maybe that reduced amount is meant to apply only to those who fertilize frequently (weekly, weakly), and if we are only fertilizing once or twice a month, the directions on the container are proper?

Finally: I have used up my current supply of MSU fertilizer and I'm reluctant to buy more since it takes me so long to use it up. I currently have in my cupboard the following liquid fertilizers, all Schultz brand:

Plant Food Plus, 10-15-10
African Violet Plus, 8-14-9
Cactus Plus, 2-7-7

Is it safe to use any or all of these on my orchids?

I don't think that even when it cakes up, that fertilizer goes bad... it is a mixture of inorganic salts that tend to absorb moisture but don't change chemically. I have a 25-pound sack of MSU that I'll probably be working on for the rest of my life (and I have a large collection...) I keep the sack (with a clip to keep it closed) inside a plastic bucket with a tight-fitting lid and it stays nicely dry. For using it, I put a littlle in a small jar with a tight-fitting lid, which takes me a couple of months to use up. In that amount of time, it does pick up a bit of moisture - I start with powder but end up with little balls of fertilizer. But I treat it the same when measuring.

As far as amount is concerned, doesn't matter whether the fertilizer is labeled for orchids or not... fertilizer is fertilizer. You use a small amount (1/4 to 1/2 of what is on the label) because orchids require only a little bit, but want it more often. Just as you would prefer three modest-size meals per day rather than a huge banquet once a week with nothing in between, orchids are similar in their needs. In nature, they hang from trees and get a very small amount of nutrients washing down on them with rain, nearly every day. I'm no expert on the fine points of fertilizer, but looking at the formulations, I'd guess that the Plant Food Plus is the closest to the usual orchid formulations... a bit heavy on the phosphorus that the orchids don't need much of but won't hurt. (Might help with hard, high-pH water since phosphorus is probably phosphate, a bit on the acidic side) The other two are light on nitrogen, which is the nutrient that would be most useful. They're not "unsafe", just may be less "satisfying".

It happens to me also but I keep using it. Like Roberta said, it's just a mixture of inorganic salts. Some salts change color when hydrated (water absortion). That's why it turns pink.
The fact that it forms clumps may change the concentration but, as the clumps make its volume higher, the concentration will be lower, which is better than higher. Anyway, it will result in minor concentration changes so no issues will come out of that.

Store it in your freezer. It won't clump.

The only part of this I won’t “blanket” agree with is the “use 1/4 to 1/2 the recommended dose” stuff. It’s a little too loosey goosey for me.

Pick a target nitrogen loading and use that amount, no matter the formula.

Ah-ha! I will definitely try that next time. Thanks for the replies, all of you. I won't worry about fertilizer granules changing color or texture.

Ray, I've read many of your site's feeding articles, and I'm trying to digest all of the information. No pun intended. :)

Mountaineer ----- if that fertiliser you have are granules ------ and not liquid, then one way to get a rough idea about how much to use is with the simple calculation shown at this link here. The value of 'T' could be just set permanently as 0.01. And then you just have to put in how much water you are going to use ------ such as 500 mL or 1000 mL etc. And "N" will just be the number on the packet .... (from the N-P-K specifications).

I think that even if a fertiliser is in a liquid form ------ the formula should still be workable ..... except just switch the units of the quantity "F" from mL to gram for the amount of fertiliser needed ----- as an approximation.

I personally do what Roberta does as well. I just know roughly what the manufacturer of my orchid's fertiliser recommends for orchids ------ written on the bottle. And then I just really do just use one-quarter or even one-third of what they recommend. And once we have a measuring device (eg. teaspoon, or syringe for liquid etc) ------ we can just use that as a reference ...... and mix more or less the desired concentration every time.

Although - if ever in doubt, or for serious control of fertiliser concentration ----- we can certainly use the formula too.

I use Akern Rain Mix that comes with a small spoon (1 gr). The recommended dosage is 1 gr. per 2 l of water so I fertilize in every watering with half that dose. Depending on the genus and the season, I may use 1/4 dose, full dose or none.

It’s the mass of nutrients applied that’s important, and that is controlled by the concentration of the solution applied and the frequency of application.

Just think of it like counting calories when eating. You can eat several small meals or one large meal, in order to reach 2000 calories, for example.

I have found that applying 75-125 ppm N per week is a good overall concentration to shoot for. (Yeah, I know it’s a concentration, not a mass, but as we really have no idea how much of the applied solution is absorbed by the plant, it’s an acceptable control.)

6/%N in fertilizer = teaspoons/gal for 75 ppm N
8/%N for 100
10/%N for 125.

Multiply by 1.15 if you prefer your measurements in ml/L.

At the risk of embarrassing myself, I'm just going to say it. I am not good at advanced mathematical formulas.

My main question was about the age of fertilizer and whether that made it any less potent, and I understand now that it does not.

In my question about the weekly/weakly philosophy, I was just wanting clarification. The answers here reaffirm for me that actual amounts as far as teaspoons per gallon are going to vary based on the composition of the fertilizer I am using and how often I use it.

I have tremendous respect and admiration for those of you with advanced scientific knowledge and math skills, and I do appreciate the replies. :)

Yes, the basis for everything in this field is the chemical composition.

Not at all! With that formula ----- all you need to do is to see the fertiliser bottle --- to find out what the 'N' value is.

The packet will have an N:P:K (ie. NPK) ratio .... such as 11:36:16

The left-most number in this case is '11'. So that's all you need to focus on.

And the other thing you need to focus on is how much water you plan to use for your mixture. Eg. half a litre is 500 mL. But you might plan to use more water, such as 3 litre, which would be 3000 mL.

Let's just say you plan to use 3000 mL (ie. 3 litre) of water. And let's just say we want to find how much fertiliser is needed for that 3000 mL of water.

Then all we do is to take the number 3000, then divide it by 100 (which gives 30), then divide by 11, which gives a value of 2.7 gram. That just means we need to add 2.7 gram of fertiliser for three litres of water.

In the above example ---- the '11' is the N value (and your packet of fertiliser might have a different N value). And the dividing by 100 is just part of the formula.

So just a re-cap. If 3000 mL (ie. 3 litres) of water is to be used ..... and if the N value is 11, then all you need to do is to get a calculator, and do (3000 divided 100), and then divide 11. The result will be the required mass of fertiliser you need to add to 3000 mL of water.

SouthPark, I appreciate you trying to help me, but I live in the USA. I'm used to the Imperial system of measurement. I know little about the metric system.

I know that the nitrogen percentage is the first of the three numbers in the fertilizer formula. So how would I figure out the amount of fertilizer to put in a 2-quart watering can? (I don't have the storage space to mix up fertilizer water by the gallon ahead of time.)

No problem Mountaineer!

If you take the number of quart (Q) ----- in this case 'Q = 2', then just multiply Q by 9.46, then divide by the 'N' value ----- you'll then get the amount of fertiliser needed (in units of gram).

So if your packet of fertiliser indicates N = 11, and if Q is 2 quart, then just take the value of 2, then multiply it by 9.46, then divide by 11.

Or - if we make it easier ..... we just take 2, then multiply by 9.5, then divide by 11 ------ which will give 1.73 gram.

This means to just put approximately 1.73 gram of fertiliser into 2 quart of water.

This is getting a little comical. :biggrin: Again, I'm not someone who uses the metric system in my daily life. I don't have the ability to measure something in grams. That's a weight measurement, not a volume measurement, right?

I use teaspoons, or fractions thereof, measuring fertilizer out by volume. If I was to measure by weight, I would have to use ounces, but that wouldn't work because the amount I would use would be so small it wouldn't even register on my scale.

When I had the MSU fertilizer, I was using a quarter-teaspoon measuring spoon and filling that about three-quarters full and putting that much into a 2-quart watering can. At this point, I honestly don't remember how I came up with that amount, but it was based on the manufacturer's directions, which I was cutting either in half or quarter.

That's what I do with my MSU fertilizer... I use a 2-gallon pump sprayer, put in 1 teaspoon (which comes out to 1/2 teaspoon per gallon) So for 1 gallon I'd use 1/2 teaspoon, for 1/2 gallon (2 quarts) 1/4 teaspoon is what it comes out to. Is it precise or scientific? Not particularly, but close enough for the orchids.

Hey, you asked what time it was, and lots of people are telling you how to build a clock. :biggrin: I prefer to keep it simple... It works.

Another approach...your MSU fert is NPK 13 3 15. That means, roughly, for each gram of fertilizer, 13% of this weight will be nitrate, 3% will be phosphate and 15% will be potassium.
Easy, no?

This is helpful because it's very close to the amounts I was using already, and it's in measurements I understand. :blushing: My question concerning amounts of fertilizer were just along the lines of wondering whether the way I've been doing it is similar to what others are doing.

I'm grateful to everyone who has responded, including those who gave me precise mathematical formulas and the scientific reasons behind them. I guess I will be in big trouble if and when the US ever officially adopts the metric system. :)

Absolutely no problem too.

If Q = 2 quart, and let's just say N = 11, then use this calculation to get the amount of fertiliser in teaspoons.

Take the 2, and then multiply by 1.5, then divide by 11. That will give 0.27 TEAspoon.

That could be rounded down to 0.25 ..... a QUARTER of a teaspoon of fertiliser for 2 quart of water.

That confirms Roberta's amount.


For a number of quart (Q) of water we want to use, and assuming we know the value 'N' (the percentage of nitrogen - obtained from the N-P-K details on the packet), and assuming 100 part-per-million nitrogen we want to have .......... and assuming roughly 6.25 gram per teaspoon of fertiliser ....... just take Q, then multiply by 1.5, then divide by N.


So if say N = 13, and Q = 2 quart, then the number of teaspoon needed is 2 times 1.5, and then divide by 13 ----- giving 0.23 teaspoon ---- which could be rounded to 0.25, or one-quarter teaspoon.

So for 2 quart of water used ------ the quarter-teaspoon amount is just fine.

That's for N = 13 ---- and for making a mix with 100 part per million nitrogen ------ or aka 0.01 percent nitrogen.


If N were 6 instead of 13, then the result would be half a teaspoon of fertiliser.

But ------ even using one-quarter teaspoon should still be workable. Not precise, I agree. But still workable.

"Hey, you asked what time it was, and lots of people are telling you how to build a clock. I prefer to keep it simple... It works."

Cheri, I understand. This is why I rarely ask questions anymore. FWI, there are metric conversion apps for your phone in the rare chance you need one.

The fact is that fertilizer dispensing should be done by mass, as it’s the mass of nutrients that’s important to plants, not the amount of dilution. Measuring powders by volume is a guesstimate at best, because the bulk density (mass per volume) varies.

One way around that is to make a liquid concentrate from a known weight of powder.

Or if you just want to stick with powders, here’s a calculator to help with units, both mass and volume estimates.

Sure - we can make a clock hehe. But not just any clock.

With one of these bits of hardware here ----- you can make a time clock that loses say only 0.0005 second per year. Or even significantly less than that with some extra work.

Not that there is actually a need for one, as I have a watch, and cell-phone, computer etc that tells the time.

This is strictly for occasions when somebody asks what time it is hehehe.


http://www.orchidboard.com/community...1&d=1616501341

I was really hoping there was going to be directions
To make a sun dial!



FYI. I did all the above and then found the exact scoop I needed to avoid thinking. I got a 1/3 tsp which is ideal for using Klite in a 2 gallon sprayer.

I keep the scoop in the fert lol. Not thinking about that ever again

That is simple and understandable. Thank you.

Umm, not on my old-fashioned flip phone with no internet connection. :blushing: I can of course find such conversion sites on my computer, but I'm just stuck on the Imperial system and prefer not to have to do lots of math on top of math. :biggrin:

---------- Post added at 09:02 AM ---------- Previous post was at 08:57 AM ----------

Thanks, Ray. In perusing the wealth of information on your site, I'm not sure I had come across that simple calculator yet. It looks easy, and I will give it a try.

You're 100% on target Cheri... what a comedic thread to read.

Once anyone uses a + or - or = sign along with the alphabet to explain measurements and formulas, I'm outta there! Along with metric and centigrade.

I'm with DC from the standpoint of figure it out once, find the right container to measure with, and keep it next to the fertilizer. The only difference is when I go from one size watering container to a larger one... I tried once to do the calculations for it. It was so much easier to message Bill and just say Please do the calculation for me, but please don't explain it. I think I've hooked DC into doing that for me a couple of times as well. Works wonders for me. :biggrin:

Now a sundial? I'm in! Wouldn't that be a fun project?

Most welcome!


If you know in advance what the 'N' number is, such as N = 11 percent nitrogen ----- then you can get a multiplying factor ..... M.

M will just be 1.5 divided by N. That is, M will be 1.5 divided by 11. This gives M = 0.136

The '1.5' value is just a pre-determined value, in case anybody is wondering where that number 1.5 came from. It comes from the relation 1 quart is 946.353 mL, and an assumption of 6.25 gram per teaspoon of fertiliser, and an assumption of 0.01 percent nitrogen that we want to create. (946.353/6.25)*0.01 is where the 1.5 comes from.

If your actual N value on the packet is not 11, then just put the relevant number (eg. 10, or 10.5, or 13 etc).

So let's just say our multiplying factor turns out to be 0.136 (for M). That's one of the two numbers you need for your own fertiliser. The other number is 2 quart.

So you just take 2 (quart) and multiply by M. That's 2 times 0.136. That leads to the amount of fertiliser you need in TEAspoon ..... which is approximately 0.27 TEAspoon. This can be rounded down to 0.25 TEAspoon. That's one-quarter of a TEAspoon of fertiliser (with N value of 11%)

So the math would just boil down simply to 2 numbers to be multiplied together. And then that formula can be applied to pretty much any general amount of water that we would use for home-type orchid growing. Eg. 2 quart, 3 quart, 4 quart, 5 quart etc.

So for 4 quart of water ...... we just do 4 times 0.136, leading to approximately half a teaspoon of fertiliser (with N value of 11%).

I have never understood why people would buy an orchid specific fertilizer then look at the instructions and but use at half/quarter strength. The stuff us made to be used ON ORCHIDS at the stated strength. Potty.

Each orchid grower has their own fertiliser schedule. Some do the relatively 'weak' application more 'often'. While some might apply some other concentration once a month, or twice a month.

Sometimes - if a grower applies the bottle recommended amount too often ------ and depending on what media or pot or whether any regular flushing is used or not (to flush out accumulated salts) ----- then there can be some negative impact on orchids arising from too much salt build up.

what size teaspoons do you use in the States/Australia? I've just checked the ones in my drawer using a syringe of water and I've got 3ml, 4ml and 5ml!
And on that subject what on earth is a 'cup' in food recipes? Do you all have identical cups in your kitchens??
Great thread!

Fuerte ----- use this converter here.

The conversion of 1 U.S. teaspoon to mL is approximately 5 mL.

I think that ----- to totally avoid mistakes ----- probably best state the type of teaspoon ... eg. U.S. teaspoon ..... and even state the assumed quantity, such as approximately 5 mL.

Or imperial teaspoon, and also state the associated mL quantity --- approximately 6 mL for imperial teaspoon.

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.

But...

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

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.

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.

The ratios are identical.

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.

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 😊

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

Oh Bill??? YooHoo! Are you there? :biggrin:

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!

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!