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[APD] Re: Aquatic-Plants Digest, Vol 5, Issue 40
> Message: 9
> Date: Mon, 12 Jan 2004 01:32:18 -0500
> From: "Thomas Barr" <tcbiii at earthlink_net>
> Subject: [APD] RE: K+/Ca++
> To: aquatic-plants at actwin_com
> Okay found a bit more to back up my claims:
> Calcium, magnesium, and potassium compete for the same sites of absorption
> by the plant; so increasing one may decrease another.
> We have said in the past these sites are different due to the valancies of
> the cations in question, but I think from what I've read that is stil
> but the over all salinity/dissolved ion content/hardness influeces the
> sites, not just one particular ion.
Then is possible high K blocks Ca?
> Using more NO3 vs NH4 also helps decrease any higher K+ effect.
> High temps also were cited for increases in Ca+ blockage.
I use very ofen NH4 (I know what are you thinking, but I havent algae
> Ca+ is transported only in the xylem, not much of an issue in aquatic
> plants but there is transport of nutrients in the vascular tissue((See Ole
> Peterson) and perhaps fluxes in K+ can cause changes if the Mg/Ca/K+
> are off somehow.
> >From hydroponic's research: K+ Toxicity - saline condition, marginal leaf
> burn, wilting and drying due to poor water uptake.
> These are symtoms of excess K+. But this does not sound like the reported
> aquatic growing tips.
> So perhaps low Ca, Mg?
> I think the likely hood of low Mg seems a more likely candidate because
> people have EVER tested for Mg.
> I have always added Mg at 4:1 ratio with Ca, not just using CaCO3 or CaCl2
> alone if I rasied my GH, and also suggested Dolomite which has Ca, Mg and
> CO3 in place of CaCO3.
> Has anyone even suggested or looked at Mg?
> Tested for it?
> Ca++ alone for that matter?
But Mg deficiency is more or les simimlar to Fe deficiency (yelowing tips)?
> In most of the hydroponic literature and horticulture, I found solutions
> 150-500ppm of both K+ and Ca++ recommended.
> Clearly at these levels, which are over 3x the max levels I used in
> aquariums, there should be no inhibition of Ca if you have enough Ca+ say
> 1:1 ratio of K+ to Ca.
> I've said it for a long time, I don't see the the effect on my plants.
> Folks really wanting to understand why they are having problems when they
> dose K+ may want to measure the Ca++ and the Mg++ and get a good handle of
> the K+ levels, perhaps do bigger water exchange top re set things then be
> careful in your measurements.
> Also, what is the soruce of K+ that folks are using here? KCL or K2SO4?
I my case nitrate and sulfate necver cloride
> That will also help.
> Many have not reported any ill effects with KCL, but I have used
> exclusively K2SO4.
> GH is another thing that is needed. Ideally Ca++ levels. Salt water Ca++
> test should work fine and be available also.
> Much of what I've read suggests Mg deficiency and some do not mention
> anything about Ca++ inhibition at high levels from high K+.
> A potassium excess can cause a potassium-boron imbalance, which may also
> result in transverse cracking and "brown checking".
> So it might not be anything to do with Ca++, B yields similar deficiencies
> as Ca++.
Myself sugested some possible relation with B but there are some rechearch
suporting high K blocks B?
> The other thing, high Ca++ levels are suppose to cause K+ deficiency, I've
> had extyremely high Ca++ levels 400+ppm, lower K+ levels at 10-20x less
> than Ca.
> I've never seen any signs of K+ deficiencies.
> While some of the older plant books and even some coming out today suggest
> that plants prefer soft water, one things was clear that plants prwefer
> moderately hard water. Excessive Potassium can inhibit Nitrogen uptake.
> Excessive calcium can inhibit Magnesium uptake.
> Some high/low K+ levels in _SOIL_:
> low: < 150 ppm (< 0.4 meq/100 g soil)
> high: 250-800 ppm (< 0.6-2.0 meq/100 g soil)
> excessive: > 800 ppm (> 2.0 meq/100 g soil)
> Magnesium, manganese, and calcium deficiencies become more pronounced with
> excess K.
> An adequate soil supply of boron must also be maintained in order to
> optimize the utilization of K (to support active root development for K
> Most plants simply will not take up excess K+ once they reach their limit.
> Excess K+ is very rare in soil, and at the levels mentioned, I think 50ppm
> is not much K+ in the water column truthfully.
> The problem is more complex than a simple K+/Ca++ issue, there are issues
> with Ca/Mg/B/Mn and K+ ratios.
> Tom Barr
I thing you have opened a lot of possible explanations, and maybe several of
them work togheter. And Maybe the imbalances K wit Ca or wathever, should be
the explanation the more apropiate
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