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Mixing fertilisers to own ratio: safe/effective?

Posted by sutremaine UK S. Wales 9 (My Page) on
Mon, Aug 29, 11 at 22:30

I have two fertilisers: Chempak bonsai fertiliser (10-30-30) and potassium chloride (0-0-60). If I mix two parts of the chempak to one part of the KCl, does that give me a 6.7-20-40 (1:3:6) fertiliser?

Better still, are there any ready-made fertilisers that are low in N but have P and K in a 1:2 ratio? I'm growing cacti in British gloom, and witholding N while providing all other nutrients seems to be the best way of growing something that's tough as boots and nicely-spined.

This might also be useful for a number of the 'touchy' species. Some cacti can be grown as lime beachballs, but others will simply roll over and die if they're allowed to luxuriate (some of the desert rats do this even when grown in their native climate. No-one's figured that one out yet). I'm sure some growers have tried the everything-but-N approach, but I've found very little information on the composition of each grower's fertiliser. Pots and mixes, those topics can run to several pages, but nobody really talks about what they feed the plants once they're homed. Perhaps it's because the dominant mix online is based on John Innes and grit, and therefore comes with its own supply of fertiliser.

There's an interesting hexalogue linked at the bottom of the post that gives the kind of information I'm interested in. Not only does it extol the virtues of a coarse, mineral mix in which all ingredients have their use, it suggests the use of mineral ingredients that by themselves sustain the plant for much of the growing year.

So... thoughts? Sorry if this is a bit rambly, I'm better when I have a topic to aim at.

Here is a link that might be useful: Article by Dag Panco de Grid

Follow-Up Postings:

RE: Mixing fertilisers to own ratio: safe/effective?

Well if you don't care about N really at all you can get a x:2:1 with Potassium Nitrate and Monopotassium Phosphate.

1 : 3.76 : 7.51 would be the actual ratio NPK ratio. That keeps your 1:2 PK ratio with a low N (lower than you asked about). To get that ratio in a liquid form it would be 354g of KNO3 mixed with 793g of MPP in 1 liter of distilled water (note that it will be less water actually - fill a container 50% full, mix in ingredients, fill up to 1 liter mark).

You'll have to look into the compatibility of KNO3 and MPP - I haven't tried mixing them before. This will almost certainly be your cheapest solution if you can get KNO3 where you are - it's an oxidizer and is sometimes strictly controlled. Cost per liter where I am comes to about $3.

I would stay away from high concentrations of potassium chloride... you tend to get way more Cl than you want in those formulations.

If you want to get into mixing your own fertilizers then HydroBuddy is very helpful. Most useful for liquid fertilizers. I suggest you check it out.


Sigh, as usual I typed faster than I was thinking - I meant: "x:1:2" - you get the idea.

RE: Mixing fertilisers to own ratio: safe/effective?

That looks like a handy program, thanks. I'll sit down with it once the current round of repotting is over. Hopefully it'll tell me about the chlorine content as well. I don't use tap water, so maybe I can safely use some KCl. Got no other use for it...

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