Return to the Soil Forum | Post a Follow-Up

 o
Acidic Vs. Alkaline - Root Function

Posted by landdesigner27 6 (My Page) on
Tue, Mar 26, 13 at 6:59

Can anyone explain in layman's terms why a plant will prefer either acidic or alkaline soil?

If a soil is too alkaline and the plant likes acidic, what is going on inside the plant?

Does it affect osmotic pressure in the plant? Do the cells in a particular plant need certain minerals or nutrients that can only be found in acidic or alkaline soils?


Follow-Up Postings:

 o
RE: Acidic Vs. Alkaline - Root Function

  • Posted by ericwi Dane County WI (My Page) on
    Tue, Mar 26, 13 at 9:50

This is a partial and incomplete explanation. Since plants don't have legs, fins, or wings, they must grow where they are rooted. If a seed germinated in pH neutral soil, and the pH drops due to, say, 6 inches of volcanic ash, the plant must adapt or die. The Ericaceous family of plants, which includes rhododendrons, blueberries, azaleas, and heather, is adapted to acidic soils, where the pH value would measure more than 4, and less than 7. To my knowledge, all of these plants live in association with mycorrhizal fungi, which are also adapted to grow in acidic soil. With blueberries, the plants fail to absorb iron when the soil pH is too high, and the leaves develop yellowing between the veins, which is termed "iron chlorosis". I don't know if this condition is due to poor iron uptake at the root, or poor iron uptake at the fungi. Fungi are thought to rob the plant of carbohydrate, and supply the plant with nutrients from the soil.


 o
RE: Acidic Vs. Alkaline - Root Function

Your soils pH has some affect on the ability of a plant to uptake nutrients. However, some plants have evolved to grow in fairly acidic soils, Blueberries, Rhododendrons, heaths and heathers, but most do best in slightly acidic (6.2 to 6.8 pH) soils and that range is where most all nutrients are mostly available. There are some few plants that have evolved growing in more alkaline soils but even these do not do well in soils with a pH much higher than 7.5, mostly because most nutrients get tied up and are not readily available to the plants.


 o
RE: Acidic Vs. Alkaline - Root Function

In order for plants to take up nutrients they must go into solution. That is, they must dissolve so that the plant roots can take them up along with water.

If the pH is too high (aka "alkaline", the opposite of acidic) plant nutrients, especially metals like zinc, manganese, copper, and iron, don't dissolve and are in relatively large chunks or "precipitate". The plant roots have tiny little holes and these large chunks physically can't move into the roots. It would be like you trying to eat an orange through a straw.

When the pH is too low, (acidic) then you get too much of a good thing. If too much of the plant nutrients in the soil go into solution, you get an overdose and end up with toxicity issues. One of the biggest players in toxicity secondary to low pH is aluminum.

As mentioned above, some plants are adapted better to one condition or the other but must plants like the soil to be slightly acid but can tolerate a relatively wide range of pH values.

Also as mentioned above, beneficial microbes that process organic material into plant available nutrients function best within a certain pH range and are less effective at very high or low pH values.


 o
RE: Acidic Vs. Alkaline - Root Function

Cool. Thanks for the info!

How does Hollytone lower a ph....which ingredient?

And the 4-3-3...is that percentage of N K P per 1 serving?


 o
RE: Acidic Vs. Alkaline - Root Function

So garg, is the common sign of too much acidity in vegetables, yellowing and failure to grow, actually N deprivation because elements such as aluminum have displaced it from the solution?


 o
RE: Acidic Vs. Alkaline - Root Function

Aluminum is toxic to (most) plants and humans.

It doesn't effect N availability very much, but it effects root growth a whole lot. The root tips and membranes "burn" unless the plant has a tolerance to the aluminum. Rather than "burn" I guess I should say it prevents cell division/transport.

In higher pH soils in a lot of areas, there's generally just as much aluminum in the soil...it's just in forms that are plant unavailable.


 o
RE: Acidic Vs. Alkaline - Root Function

Someone in florida was telling me that the higher ph soils have big problems with aluminum.


 o
RE: Acidic Vs. Alkaline - Root Function

1) Yeah, what nc-crn said.
2) Someone is Florida is confused. That is, unless, they were talking about not enough aluminum. That's not very common unless your triangle palm isn't blue or your blue hydrangeas are turning pink.

This post was edited by gargwarb on Fri, Mar 29, 13 at 10:43


 o
RE: Acidic Vs. Alkaline - Root Function

  • Posted by glib 5.5 (My Page) on
    Fri, Mar 29, 13 at 11:31

But consider, for example, the same plant in pH=5.5 and pH=7.5 soils. There is a difference in certain ions availability of a factor 100. That same plant does or does not change any micro-physical or chemical characteristics of its roots?


 o
RE: Acidic Vs. Alkaline - Root Function

Actually come to think it was said in regard to high CEC, such as the muck soils of florida.


 o
RE: Acidic Vs. Alkaline - Root Function

But that is also odd, because higher CEC would generally correlate with higher ph. Below is a UF page about aluminum in sandy soil.

Here is a link that might be useful: as well as EC


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Soil Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here