Hi Chris this kind of rambles a lot, it such a big subject, but hope it makes sense.
I think the fact that so many people are able to successfully grow so many species in so many different types of soil, with so many different water sources and types of fertilizer, is pretty strong evidence that most plants are not too specific in their needs regarding soil pH. Of course, the phrase "successfully grow" is rather subjective, as there can be a big difference between keeping a plant alive and having it really thrive.
I wonder how many simply give up because they have water issues they are unaware of. I know when I started I took it for granted that the water out of the tap was fine for my plants. If I had started bonsai where I live now, I would not have persisted for long at it.
Paul, I know we've had similar discussions about these issues before but I'm still trying to wrap my head around it all. It leaves me with one question about miracid - is it all just marketing hype or is there something about it that does make "acid loving" plants healthier? Maybe the trace elements? Lots of people claim that it does work but the research evidence seems to indicate that it does not really do much if anything to lower soil pH.
I reread Argo and Fisher and they only mention urea in terms of slow release fertilizers and interestingly, in the glossary near the back of the book:
"Urea nitrogen - An organic form of nitrogen that tends to decrease pH of the soil solution over time."
I think that referring to slow release pellets and over a period of time is telling.
Miracid is about giving a big dose of urea in one hit, like in an agricultural setting. You have to remember that these products are designed for ground use (and making profits for the company as urea is very, very cheap). Soil behaves completely differently to a potting mix. I think where people are seeing positive results with Miracid is that they fertilize only once a month or so, there pH is OK but they haven't tested it; and when they give the trees a hit of miracid, they get a response from the N, P and K that's presented to it, not from any change in pH.
I know I read somewhere but can't remember where - that plants tend to use nutrients in a ratio very unlike what most fertilizers contain. Something like 13-1-1? And I've seen the comment about potential problems due to excessive potassium before. So does it make sense to find a fertilizer that has very low K? For instance, something like
Excessive anything is bad, the only element that doesn't cause toxicity is calcium, but too much of it inhibits potassium and magnesium uptake. Forget what people say about plants only taking what they need and the rest washes out of the potting mix, if you have too much K, or copper, or iron, or magnesium in your soil, it will cause problems with toxicity. You have to "balance" K with all the other elements in your mix, it's not as easy as just getting a low K fert, or a high Mg fert.
This formula (12-1-1-10Ca-3Mg) has been developed in response to recent studies suggesting that excessive potassium, whether applied-, obtained from- or accumulated in growing media, can have a negative impact on the health of plants, especially in the absence of adequate calcium and magnesium levels
Welcome to the Darkside, Luke, er, I mean Chris. Welcome to the world of hydroponics. Your officially moving into forbidden territory now. I can hear the flat Earthers stirring.
"Noooo; this is science, we can't have science in bonsai."
Jim's head is about to explode.
"Sacrilege, this is against the gospel of Brent!"
But simply put, too much K can have an impact, Yes.
But the important point is in the absence of calcium and magnesium. If there is too much Mg and Ca then the tree will become K deficient. It's a balancing act. Generally there is a suggested ratio of K:Mg:Ca but this varies from species to species. It's a tough call to say what it should be for anything other vegetables, generally it's quoted as Ca should be twice that of magnesium, and potassium is half of Ca+ Mg. But its highly variable, so you may not get a fertilizer that suits, especially in a one off dry fertilizer because calcium forms insoluble salts with phosphate, so you can't have them together. Also your irrigation water might be quite hard, and so you may not have to add any calcium to you fertilizer. In which case you have to find a fert with high magnesium and K to suite. It gets rather difficult from here for the average bonsai-ist. But basically you have to get a complete water test done on your irrigation water and then make you own fertilizer to suite. Not something the average punter wants to do. And really, it's only if you have crap water, if you have good water all you have to do is sprinkle some gypsum on the pot every month or so, and add a little bit of epsom salts to your fertilizer.
I fertilize every time I water, so my concentrations are much lower then what fortnightly people would use. Currently , my water has some bicarbonate in it, and some sodium, which is why I fertilize every time I water.
Sodium is not so good for plants, as it displaces potassium from stomatal guard cells preventing them from closing, leading to marginal leaf necrosis (burn). To counter this I have slightly more potassium then sodium in my water, I then balance calcium to magnesium depending on the level of K. So it's something like 35ppm K, 40 Ca and 16 Mg. But last summer I got lazy and just hung a stocking with gypsum in it into the fertilizer tank and whatever dissolves is my calcium level. So I'm not so fussed about K:Ca:Mg, what I am fussed about is ammonium and phosphate and these levels are way down on what people imagine they should us. So I would recommend a low N & P fert with higher K and then add gypsum and epsom salts to suite, or just use organic fertilizers, they seem to work well.
Regards
Paul