Question about fertilizer and PPM measurement

[Alvaro78]

Hello guys!

This is my first post on this forum but I have been lurking for some time now and I have been able to learn a lot from you guys so thanks a lot!

Now my question is related to fertilizing. I have bought the Rain Mix fertilizer which is based on the MSU formula but this one is available in Europe. I was planning on mixing the fertilizer with my tap water since I live in an area with soft water but... I was wondering if you could tell me if the quality of my water is as such as I don't have much knowledge on how to read water quality. I am going to attach a picture of the water quality of my area which if I am reading correctly has 22 ppm so would that mean it would be safe to use with the fertilizer? I was also planning on using the value recommended which is 0,5g per liter of water
Sorry that the screenshot is in Spanish but from up to down it says:

- Calcium
- Hardness (the important value I think?)
- Magnesium

Then in the next column the values are the yearly average

Thanks a lot for reading all this and for the help! <3

[estación seca]

Hello Alvaro, Welcome to the Orchid Board!

You are correct, your water has low amounts of minerals. The Rain Mix formula is appropriate for your water. The well water formula is designed to lower pH of water that normally has more dissolved minerals and a higher pH. Using the well water formula with pure water may lead to a lower pH than is desirable.

I'm not familiar with Rain Mix. Unless it has calcium you may need to provide calcium feeding for your plants. The MSU pure water formulation in the US does contain calcium.

[Alvaro78]

I see, thanks a lot! Just a couple of more questions with the well water formula do you mean the formula the MSU fertilizer uses? Sorry for not understanding. The other question is related to pH apparently my water pH is 7.8 and since I know the Rain Mix fertilizer acidifies the water do you think it would be ok?

And yes the Rain Mix fertilizer has plenty of calcium and magnesium

[Ray]

That data is incomplete. Yes, you only have about 12 ppm Ca + Mg, and the alkalinity is low, but I wonder what else is in the water that keeps the pH above neutral.

That said, I think the Rain Mix will be fine, and I suggest that you divide 9.2 by the nitrogen content. The result is the ml/L to use for weekly feeding, and may be rounded to the whole ml for convenience.

[Alvaro78]

I have attached more data of my water quality but sadly I cannot really translate it but I think most names are similar in english.

By dividing the N by 9.2 the result I get are the grams I would be using for fertilizer? In this case it would be 0.77g per liter I don't know how much it would change if it was grams instead of ml as you suggested.

One last question do you think I should reduce the amount of times I fertilize (every watering) when winter comes?

Thanks a lot!!

[estación seca]

Different orchids have different fertilizer requirements. Orchids growing in ideal conditions grow faster than orchids in less-ideal conditions. Faster-growing plants can use more fertilizer. The concentration used varies with fertilizer frequency. Gardeners use lower concentrations when fertilizing at evey watering and higher concentrations when fertilizing weekly or monthly.

Most orchids don't grow much in winter, so fertilizer is reduced or stopped. Some do continue growing so fertilizer is still used.

Ray didn't mention it but on his Web site is a large amount of information on fertilizing plants. I suggest you read it.

[Alvaro78]

I''ll check out Ray's guide thanks a lot for mentioning it!

[Ray]

Originally Posted by Alvaro78

I have attached more data of my water quality but sadly I cannot really translate it but I think most names are similar in english.

By dividing the N by 9.2 the result I get are the grams I would be using for fertilizer? In this case it would be 0.77g per liter I don't know how much it would change if it was grams instead of ml as you suggested.

One last question do you think I should reduce the amount of times I fertilize (every watering) when winter comes?

Thanks a lot!!

That’s not much more helpful from a plant nutrition standpoint, I’m afraid, but it’s still good water.

Yes, I meant ml, not grams, for fertilizer estimation.

Mass is certainly the more precise way of measuring - a ppm is 1 mg/kg, so my recommendation is 100 mg/kg of solution, but most folks can measure volume more conveniently, and estimating powders at 1g/ml density isn’t going to be far enough “off” to make a significant difference that that final concentration.