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

[SouthPark]

Originally Posted by Mountaineer370

This is getting a little comical. 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?

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.

[Dollythehun]

"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.

[SouthPark]

Originally Posted by Dollythehun

"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."

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.

[Mountaineer370]

Originally Posted by SouthPark

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.

That is simple and understandable. Thank you.

Originally Posted by Dollythehun

"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.

Umm, not on my old-fashioned flip phone with no internet connection. 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.

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

Originally Posted by Ray

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.

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.

[SouthPark]

Originally Posted by Mountaineer370

That is simple and understandable. Thank you.

Most welcome!

Originally Posted by Mountaineer370

prefer not to have to do lots of math on top of math.

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%).