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

[rbarata]

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

[SouthPark]

Originally Posted by Mountaineer370

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

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.

[Mountaineer370]

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.)

[SouthPark]

Originally Posted by Mountaineer370

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.

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.

[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?

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.

[Roberta]

Originally Posted by Mountaineer370

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. I prefer to keep it simple... It works.

[rbarata]

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?

[Mountaineer370]

Originally Posted by Roberta

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. I prefer to keep it simple... It works.

This is helpful because it's very close to the amounts I was using already, and it's in measurements I understand. 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.

[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.