Fertilizer Question

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Jenny St. Michel

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Hi everyone! I’ve been using a MSU fertilizer and will soon be ready to get some more but want to change brands. The fertilizer I have now is a mix of little balls/capsules and powder/tiny granules. So my question is: When I measure out a scoop do I get an accurate amount of nutrients? I try and make it 50/50 of each which is a pain and I’m sure not accurate. Should I look for one with the same consistency? Thanks so much :)
 
The manufacturer of MSU fertilizer and K-Lite is used to customers that use multiple bags at a time, so the heterogeneity was no concern. Lately, however, they have upgraded the K-Lite to uniformly fine powder.

Probably the best way to handle powders is to make a concentrated solution and dilute that for use.

When I still had my greenhouse, I used a metering pump to feed fertilizer concentrate into my irrigation water. Now that I have a much smaller collection and use a pump-up sprayer to water my plants, I have found that using powdered fertilizer is a hassle. Fortunately, my packaging supplier carries self-measuring "Bettix" bottles.

Fertilizer_Dispenser.png

A Bettix bottle has two chambers, a larger “holding tank” (to the left in the image above) and a smaller, graduated measuring or dispensing chamber on the right, connected to the holding tank by a molded-in tube going from the bottom of the larger chamber to the top of the smaller one. Operation is as follows:

  • Add fertilizer powder to the holding tank.
  • Add water to that tank and close both tops, shaking to dissolve the powder.
  • Loosen or remove the cap from the dispenser side and squeeze the holding tank until the dispenser is filled to the appropriate level.
  • Pour that concentrate into your fertilizer application jug, then replace the cap.
For example, I want to apply 100 ppm N using K-Lite to my plants weekly. From the label, I know that 100 ppm N requires 2.9g or 3/4 teaspoon of that fertilizer powder per gallon.

My Bettix bottle has a 67 ounce capacity – perfect to hold two quarts (64 ounces) of solution. I have decided to use 2 ounces of concentrate per gallon so that my concentrate doesn’t run into solubility issues, so I must add 2.9g to every 2 ounces of concentrate, or 2.9 x 32 = 92.8g (24 teaspoons) of powder to two quarts of water, giving me enough concentrate for 32 gallons of solution to be applied.

So now, I just have to shake the bottle, dispense the two ounces/gallon into my pump up sprayer, fill that with water and I’m good to go.
 
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Thanks Ray, that makes more sense. I like the idea of making a set concentration with the Bettix bottle. As the inner scientist of me wants to get the fertilizer ratios as exact as possible. One more question. I have been using 3/4 gallon distilled water, 1/4 well water, 5 drops ph down ( phosphoric acid) to get to about a ph level of mid 6. That gets me to 10ppm. Then I add fertilizer. Do you think it’s bad to consistently use ph down? And if I used Klite at 50ppm do you know about how much that would drop the ph? Sorry for all the questions!!!!
 
Yes. Unfortunately after fertilizer it’s still low 7ph. So I get my water to mid 6ph with ph down and then the fertilizer brings it to low 6ph. My water out of the well has about 65ppm. I think I may get a RO system. But unfortunately gotta wait till I recover from Xmas...
 
Jenny,

I have a very hard time accepting that 3/4 distilled water, 1/4 well water and 5 drops of pH Down results in a TDS of 10 ppm. If that's true and we totally ignore the H3PO4, that would mean your well water is only 40 ppm, which is probably fine for your slippers. Granted, I have very little faith in TDS meters.

What is the pH of that water mixture, sans acid? What is it with just fertilizer?

I doubt that the phosphoric acid at that level is a problem, but I also don't know that I'd bother lo adjust for pH 7.
 
I’m very new to fine tuning my fertilizer/water. So my goal has been to be in a ph between 5.5 and 6.5. And feed at about 150ppm. BUT I’m now learning I should be basing this off my N ppm. I have a cheap TDS meter, decent ph pen and liquid ph test kit. I think we have decent water cause it tests at 60 to 70 ppm. I had a water sample done and ph is 7.8. Anyhow I’m trying to learn how to get the water as “perfect” as possible but it’s definitely hard! I’m working on reading your website Ray. I’m just hoping I’m not doing more damage than good while I figure all this out. Anyhow thanks for all the advice. It makes me think even more. Happy Holidays!!!
 
Start with the frequency of feeding, as that will provide some guidance as to the fertilizer concentration. I know it's an odd measure - equating concentration with mass - but I recommend frequent feeding with a total of about 75-100 ppm N over the course of a week. That can be 25 ppm three times, 50 ppm twice, or the full amount once, if you catch my drift.

Build yourself a "calibration chart" for your TDS meter. Measure your water alone. Then make up a gallon of solution with a known nitrogen concentration. For example, 5.7g MSU RO in water provides 200 ppm N (use 4.35g if you have K-Lite). Measure the TDS of that solution, draw a straight line between the two points, and you'll have a reasonable guide for that meter.

Once you've settled on the fertilizing regimen, do a pour-though test, as what's happening in the pot is a lot more important than is the pH of the applied solutions.
  1. Water your plant thoroughly with your preferred fertilizer solution so that it's saturated.
  2. Allow it to drain freely and stand for 30 minutes.
  3. Trickle about 50 ml (a 1.5 oz shot glass will suffice) of pure (RO, DI, or distilled) water over the entire surface of the medium, collecting the liquid that drains through the pot.
That's what you should test for pH determination.

You may find that your precise adjustment of the solution is unnecessary.
 
I did not invent the method, but I would think that would introduce too much dilution and make the test all about the solution and not what the plant and medium is doing to the rhizosphere.
 
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