How to measure the amount of Osmocote x Lt (or Ounces) in a Pot

[Cach26]

How to measure the amount of Osmocote x Lt (or Ounces) in a Pot

Hello everyone, Happy Growing

I recently bought Osmocote 15-9-12, although it comes with instructions for using it, this guide is based on cm. And most of my Pots (recycled Bottles and Pots XD) have their capacity described in Liters or Ounces

How can I do the calculation so as not to fertilize incorrectly?

[Grawski]

Volume Conversion Calculator

[Roberta]

Gee, I just use a pinch for a small pot, a bigger pinch in a larger pot. A 2 gallon (8 L) standard Cymbidium might get 3 pinches. It's just a supplement to my regular liquid fertilizing for plants that need more than the rest of the collection. There's no "correct" involved.

Another note about "time release" fertilizer - actually, it's more like "temperature release" At higher temperature, most products release their fertilizer faster. (Reasonable... when it's warm and the plants are growing faster they can utilize more) So any attempt to measure is futile.

[estación seca]

Many years ago at a lecture I heard a soil scientist say controlled release fertilizers are not a good idea during the warm months in my area. They release very quickly when temperatures are over 90 F / 32C.

[Ray]

If you want to be reasonably precise, you got some estimating and calculating to do.

First of all, you must convince yourself that the dispersion of the pellets within the mix will allow the percentage of applied fertilizer to be equivalent to that of a solution.

Next, you need to estimate the average in-pot temperature to determine the duration for which the pellets will release. That temperature-duration relationship is dependent upon the formulation and should be specified by the manufacturer.

Then, decide what rate you want. 100 ppm N per week seems to be a good target.

If your fertilizer is 20%N and lasts 6 months at your average temperature, then you'll want to add 26 (weeks) x 100/0.2 = 13 grams of the pellets per liter of retained volume.

The best way I've heard of to estimate the amount per pot, based upon the size, starts with weighing a container of dry potting medium, saturating it and letting it drain, then weigh again. The difference is the mass of the retained water. If you are targeting that water to be 100 ppm N - 100 mg/kg - and the retained mass was 250g, then you will simply add 0.25 x 13 g = 3.25 g/pot.

If large container of medium increased 400 g, then that's 0.4 x 13 g = 5.2 g/pot.

[Cach26]

Originally Posted by Ray

Next, you need to estimate the average in-pot temperature to determine the duration for which the pellets will release. That temperature-duration relationship is dependent upon the formulation and should be specified by the manufacturer.

This is what the company told me about the temperature-durability ratio

The average temperature is ambient, no higher than 30°C, although many other variables can cause this time to be higher or lower, such as excessive or no irrigation.

---------- Post added at 02:46 PM ---------- Previous post was at 02:39 PM ----------

Originally Posted by Ray

Then, decide what rate you want. 100 ppm N per week seems to be a good target.

If your fertilizer is 20%N and lasts 6 months at your average temperature, then you'll want to add 26 (weeks) x 100/0.2 = 13 grams of the pellets per liter of retained volume.

The best way I've heard of to estimate the amount per pot, based upon the size, starts with weighing a container of dry potting medium, saturating it and letting it drain, then weigh again. The difference is the mass of the retained water. If you are targeting that water to be 100 ppm N - 100 mg/kg - and the retained mass was 250g, then you will simply add 0.25 x 13 g = 3.25 g/pot.

If large container of medium increased 400 g, then that's 0.4 x 13 g = 5.2 g/pot.

Aja I wish it was 100ppm per week (of course we know this is subjective).

It is a 15%N fertilizer, which lasts 4 months at room temperature 27C. It would be a total of 17 weeks

---------- Post added at 03:01 PM ---------- Previous post was at 02:46 PM ----------

Originally Posted by Ray

If your fertilizer is 20%N and lasts 6 months at your average temperature, then you'll want to add 26 (weeks) x 100/0.2 = 13 grams of the pellets per liter of retained volume.

The best way I've heard of to estimate the amount per pot, based upon the size, starts with weighing a container of dry potting medium, saturating it and letting it drain, then weigh again. The difference is the mass of the retained water. If you are targeting that water to be 100 ppm N - 100 mg/kg - and the retained mass was 250g, then you will simply add 0.25 x 13 g = 3.25 g/pot.

If large container of medium increased 400 g, then that's 0.4 x 13 g = 5.2 g/pot.

So the formula would be something like this?
(weeks) x ppm / %N? = grams of granules per liter of retained volume.
Or
(weeks) x ppm /0,2

---------- Post added at 03:10 PM ---------- Previous post was at 03:01 PM ----------

Originally Posted by Ray

If your fertilizer is 20%N and lasts 6 months at your average temperature, then you'll want to add 26 (weeks) x 100/0.2 = 13 grams of the pellets per liter of retained volume.

Sorry, I'm a little slow to understand the formulas.

(weeks) x ppm /0,2
If it is this formula it would be something like this
17(weeks) x 100ppm /0,2= 8.5g?

[Ray]

First of all, it’s 6 am, the dog just woke us up to protect him from a thunderstorm, and I haven’t had any coffee yet, so bear with me on this.

A 15%N fertilizer is 150 g N per kg. If it lasts 17 weeks, then each kilogram will dump 150 g/17=8.8 g/week.

100 ppm N is 100 mg N/kg, and 8.8 grams is 8800 mg, so the proper dosing for 1 liter of pot/media volume would be 100/8800 of a kg or 11.36 g.

[Cach26]

Originally Posted by Ray

First of all, it’s 6 am, the dog just woke us up to protect him from a thunderstorm, and I haven’t had any coffee yet, so bear with me on this.

A 15%N fertilizer is 150 g N per kg. If it lasts 17 weeks, then each kilogram will dump 150 g/17=8.8 g/week.

100 ppm N is 100 mg N/kg, and 8.8 grams is 8800 mg, so the proper dosing for 1 liter of pot/media volume would be 100/8800 of a kg or 11.36 g.

Thank you Mr. Ray, for your explanation, I already understood the formula. Here I have the retained humidity data

---------- Post added at 10:51 AM ---------- Previous post was at 10:49 AM ----------

Curiously, in my 2L pots the difference in weight between dry and saturated with water and humidity was 5-15g. In my large pots it was approximately 150g

---------- Post added at 11:02 AM ---------- Previous post was at 10:51 AM ----------

So, in my large Cymbidium pots the water retained was generally 150g. (3500g dry/ 3650 wet) It would then be 0.15 x 11.36g: 1.71g for that pot, right?

[Ray]

Yes.

[Cach26]

Originally Posted by Ray

Yes.

Well, then should I multiply the 1.7 g of pellets x liters that the pot can contain? That is, a pot containing 5L should receive approximately 8.5g, and one containing 500ml receives 0.9g of pellets.