Is the additional potassium in tomato fertilizer critical?

[edweather]

I know that fertilizers like Shake and Feed for Tomatoes, Texas Tomato Food, and others, have potassium amounts around 1 1/2 times that of nitrogen. Is this additional potassium critical, or will tomatoes do ok with a basic 3-1-2 ratio. Ed

[worth1]

No it isn't and I think in many cases it is too much.
Many posters here and other places have had soil tests done using these type fertilizers and found nitrogen lacking and found too much p and k.
Nitrogen in itself is a very unstable element that can be there today and gone tomorrow depending on what type you use.
If you have a dead soil then urea nitrate wont do you much if any good.
It requires microbes in the soil to break it down to a form plants can use.
My definition of a dead soil is one where it has been hit with kills all or some such rot to kill off things you dont want but kills everything else too.
Not an expert but just a simple person that seems to stumble onto the right thing to do.

[MissS]

3-1-2 works very well in my opinion

[Rajun Gardener]

To add to the confusion watch this video of hydroponic ratios. I use it in dutch buckets but the in ground plants absolutely love it and respond in a day or two and this is with me adding triple 13 and other minor elements when I plant.

[edweather]

Thanks for the feedback. I grow mostly in containers, hope that doesn't confuse the issue too much. In the past I have used Foliage Pro, several different MGs, Texas Tomato Food, and others. My tomatoes always turn out good, and I probably couldn't tell you the difference between the results of any fertilizers I used.

[mention]Rajun Gardener[/mention] Nice video. I do have a question though. Not to hijack my own thread, .....but....when you add the calcium nitrate, doesn't that double the volume, so you just can't add 15.5 to 4 and get 19.5. Don't you have to average it, because you have diluted the 15.5, and increase the 4. So, shouldn't it be 19.5/2=9.25 Nitrogen?

[Rajun Gardener]

I'm not sure but I don't think it works that way with water soluble fertilizer. It's easier for the plant to use and it works better than anything I've ever used both in hydro or soil. In soil you can use just a TBS of CalNIt once every two weeks and you'll be amazed at the growth in your containers. You should be able to find it locally in 1 LB bags for about $14, try it in a few containers as an experiment.

[bower]

I think it must depend on your soil and growing conditions. Of course K in fertilizer is not important if your soil has lots and your growing conditions make it readily available to the plant. Growing in the north in a greenhouse I've had potassium issues in some years and the number of things that affect potassium uptake are enough to spin your head. Too much sun, not enough sun (overcrowding in my case), too cold, imbalances with other nutrients or pH can all affect potassium uptake. And genetics as well, there's a lot of variance in the gene pool that affects potassium metabolism. A potassium deficiency can give you uneven or blotchy ripening - very sad condition, you can't tell there's a thing wrong with them until they don't ripen right. Also potassium is required for sweetness to develop in tomatoes. So not sweet is another defect that can result from K deficiency.
If your tomatoes are turning out great, then you evidently have nothing to worry about.

[Shule]

That's a tricky question to answer, because fertilizers that contain lots of components have components that can interact with each other in unpredictable ways and render some things unavailable or less available. In my experience, I don't recommend relying on such for your potassium source, as the plants don't seem to absorb much potassium from it anyway, no matter how much it says it has. Tomato plants don't strictly need a lot of potassium, thankfully, but they'll be a lot more vulnerable to disease, root rot, pests, edema, and physical damage without a good supply of it, especially if they're getting more nitrogen than potassium. Tomatoes are heavy feeders and may use too much of the nitrogen at once. Too much nitrogen can lead to the same set of problems as too little potassium, and if it's extra high, it can burn plants. In theory, all fertilizer salts can burn plants if you give them too much (they all have a salt index, I mean), but in practice (in my experience), potassium sulfate seems to prevent nitrogen burn, if anything. I've never seen it come close to burning a tomato, even when I've purposefully added more than the label said to add (and it says to add a lot), and no, I'm not recommending adding more than it says to add.

If you've ever looked at the recommended amount of potassium sulfate and/or monopotassium phosphate to give a plant (on the potassium sulfate label), you'll see that it's quite a lot compared with what you'll get from pre-mixed fertilizers. I mean, it can be up to about five times as much. It's 0-0-53 fertilizer, using 1-2 tablespoons per gallon of water, for potassium sulfate. If you're used to pre-mixed fertilizers, that's a whole lot more potassium than they provide.

It's pretty hard to give tomatoes too much potassium sulfate in my experience using it on them (monopotassium phosphate, you should be a little more careful with, but they can still take a fair amount; monopotassium phosphate is 0-52-34). Is adding much potassium necessary? Not usually. Is it helpful? Often.

Potassium chloride is more prone to damaging plants, I believe. So, I'd be careful with that, if it's your potassium source.

In short, ideally potassium should be significantly higher than nitrogen—but it's not necessary for it to be higher. Neither the lack of it nor the abundance of it should kill your plants, in and of itself. It's kind of like bone health in humans. Humans can grow up and seem fine with or without super strong bones, but stronger bones definitely have advantages, and weak bones put a person at risk.

How healthy your plants are without regard to potassium makes a difference.

[SQWIB]

[mention]Rajun Gardener[/mention]

I also use Bobby's formula for my seedlings and indoor grows

What people don't realize is that you must mix and completely dissolve each component and follow a specific order, If you don't you will cause nutrient lockout. You can't just add the three components then drop into some water.


Mix for one gallon.
Fill a one gallon container half full of warm water add fertz one at a time, making sure to completely dissolve each component, dissolve each mix in a cup of hot water and pour into the gallon jug and shake real well until dissolved, top off the gallon jug.

Must mix in this order:
1. MasterBlend (2g)
2. Epsom Salt (1g)
3. Calcium Nitrate (2g).

[Rajun Gardener]

That's a good point!!! It's the calcium nitrate that takes longer to dissolve.

[Growing Coastal]

If magnesium sulfate and calcium nitrate are mixed in the same bucket of water together it turns into a gloppy mess.