Relatioship between nutrients and ph

jerime

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Jan 23, 2005
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How strong is the relationship, if any, between nutrients an ph? specificaly between low ph and nutrients : is it possible to have accurate NO3=30 and still get algae like BGA and others. Is it possible for low ph (like 5.5-5.8) to block nutrients like NO3 and others from the plants?
 

Simpte

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Feb 17, 2005
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Re: Relatioship between nutrients and ph

I was just wondering the same thing. Does PH/KH affect nutrient uptake rates directly?
 

Tom Barr

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Jan 23, 2005
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Re: Relatioship between nutrients and ph

While pH and Eh(reductive potential) are related, they are not the rest of the story.....................

Many folks miss this issue.

Plants are active, not passive when it comes to getting the nutrients they need.

Many seem to assume they are just sitting there at the mercy of the lements..........

They can and do reduce the nutrients in the soil/substrate/water column etc.
Some are better than other like the ones that can use the KH as a CO2 source.

Hydrilla adds lots of H+ and the area near the left will reduce the HCO3 to CO2 and the plant will take this up.

The pH difference on each side of the leaf is 3-4 full units........................
pH 8 on one side, pH 4 on the other.

Root zone issues are as large..........

If we are in the 5.8-7.3 range, we are pretty good.

Regards,
Tom Barr
 

Aviel Livay

Junior Poster
Feb 20, 2005
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Re: Relatioship between nutrients and ph

Tom,

I took the following chart from "normal" agriculture - you can see that phopsphate uptake is blocked first at ~ph of 6...

fertilizephchart.jpg


So maybe we should up your 5.8 low limit?

And on the other hand - people using aquasoil go below and sometimes much below your 5.8 and still get tremendous growth.

How come?

Aviel.
 

Tom Barr

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Re: Relatioship between nutrients and ph

Argiculture studies are generalized terrestrial systems, they are quite different than wetland soils.

Nutrient availability in farming is quite different than what we do.
PO4 is not "blocked", it is in a simply less available form which since the plant only needs a small amount, can easily select out of solution.
Plants can and do alter and concentrate nutrients in the surrounding soil.
This is not a difficult issue for aquatic plants. All they need to do is add a little O2 and the pH is higher, or add a little H+ and the pH is reduced.

Soil pH vs water column pH is another issue.
They can be 2 full units apart(and often are).

In terrestrial systems with less turnover, aerobic soil and large scale fertilizing, pH can play a role and improve crop production cost. Those plants can and do alter things also to take in nutrients.

It's nice to target a pH, but redox is more relevant and it is much better to think in these terms rather than pH when addressing nutrient cycling in soils.

Regards,
Tom Barr