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Root uptake of minerals

Discussion in 'CO2 Enrichment' started by Tom Barr, Jul 19, 2007.

  1. Tom Barr

    Tom Barr Founder
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    Root Uptake of Minerals

    Critical factors determining rate of uptake of minerals by plants include:

    1. Availability of the mineral. The mineral must be in a form that can be absorbed by the root. This is determined by the plant roots to some defree and the reduction in the sediment
    2. Concentration in soil. The higher the concentration, the greater the likelihood of uptake.
    3. Rate of mass flow in soil. The supply of minerals to the root is determined by the movement of the mineral in solution.
    4. Rate of root elongation. The root tip grows into soil containing fresh supplies of the mineral.
    5. Surface area of the root. The larger the contact area available for potential uptake, the greater the uptake.
    6. Mycorrhizal associations: increase the effective surface area by up to 10X.
    The factors of critical importance for each mineral differ. P, N and K are required by plants in large amounts.

    Regards,
    Tom Barr
     
  2. ceg4048

    ceg4048 Lifetime Charter Member
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    Mr. Barr
    Wouldn't point number 3. [Rate of mass flow in soil. The supply of minerals to the root is determined by the movement of the mineral in solution.] support the proponents who advocate the use of substrate heating cables? Wouldn't the thermal gradient caused by the cables provide this mineral mass flow assuming that the concentration was high enough?

    Cheers,
     
  3. Tom Barr

    Tom Barr Founder
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    Not really, can you guess why not?

    Water is moving anyway and the rate of flux between the sediment and the water column is already optimal for aquatic plants.

    They adapted and evolved in that situtation.
    They did not adapt and evolve in a heating cable environment.

    So that should make sense there.
    The rate of movement in a 10 cm deep 2 mm gravel bed is roughly 0.5liters/24 hours for no heating cables.

    You can measure optimal root redox levels using Redox probes in the sediments and measure root growth and overall plant growth.

    When you do, and review others that have as well, you find that the redox levels correlate with this flow/flux rate.

    Not higher as those produced by cables or by UG filters.

    Regards,
    Tom Barr
     
  4. FacePlanted

    FacePlanted Guru Class Expert

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    So heating cables might actually produce less than optimal conditions for root growth/uptake? They would be detrimental? or reduce growth rates?
     
  5. Tom Barr

    Tom Barr Founder
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    They might produce subtle differences in root growth, the tops of the plants however ought to be the same.

    The only advantage I could even come up with why RFUG's and Cables might help is that they rapidly pulled waste down into a new plain sand sediment.
    This prodives a source of organic carbon for bacteria in the nutrient poor sand. As the bacteria chomp away, they release CO2, NH4, PO4 etc and this material now acts a semi rich "dirty sand" sediment that's got plenty of bacteria and some nutrients now.

    So it starts that process faster.
    But then things will clog faster as well......
    You can add the nutriuents right away also, or the "dirt" or use another sediment that has the nutrients also etc.

    These are not cable related nor cable required.

    So I do find it interesting that the heat cable supportors never mentioned this one, yet enjoy citing everything that the marketing campaigns to sell them have:rolleyes:

    I do not think it's particularly significant though either way, with or without the cables if you keep the other parameters constant.
    Nobody to date has ever shown or proved they do anything.
    Plenty say they have, but you need to be able to show it conclusively and show the methods you used to test it.

    There's just not the observational evidence they do anything.
    Folks do amazingly well all over the world without them.
    Easily producing many scapes without cables as has been the case for the last 10-15 years.


    The simple test method use to determine they do not work or do anything significant: turn it off for the summer like many have too. You can turn it on/off weekly, monthly, 3 months on/off and do this several times(say 5-6X) back and forth.

    If the cables are significant, you should see growth differences.
    To date, no one has.

    I suppose if you believe enough that anything might work.But proving it to others is a higher standard.

    Regards,
    Tom Barr
     
  6. luv2fish

    luv2fish Junior Poster

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    Guess what? My first post here.
    I remember reading an intrigueing page about heating cables by George Booth. The concept mentioned in it were about substrate longevity, fluid movement within it, amoung other things. http://aquaticconcepts.thekrib.com/ Click on "Article: Substrate Heating". Im going to be installing them in my 120G im now setting up. Hope its good in the long run.
     
  7. jerrybforl

    jerrybforl Lifetime Members
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    Like Tom said, they don't really do too much! I used them for a few years and now that it's been a few years since I haven't used them....I see no significant difference in plant growth.

    It's really a waste of money! Rather invest in a nice pump or filter to give you better movenment in the tank.

    At the AGA convention in 2010, I asked Claus Christensen, formally of Tropica, about this very issue. He told me that if you really think about it; our lights/ fixtures already heat up the substrate. He was showing pics in Thialand I believe and was talking about how the substrate/ water column temp was different because of the direct sunlight. So it makes sense that our fixtures would do the same.

    The temp between the two is supposed to allow convection and pull ferts into the substrate. But if you add ferts right to the substrate its not really necessary IMO. So save your money lol! Spend it on plants or other equipment.
     
  8. Tom Barr

    Tom Barr Founder
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    George and I debated this for a few years, he finally agreed that is it's a long term subtle difference that hard to see any difference, that is also like saying the differences are insignificant and not able to measure.
    He's a real nice guy and great aquarist.

    I miss folks like him on line, really.
     
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