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Biology question - need help ASAP!!!

Discussion in 'Pesticide & Herbicide Application' started by Clear-Cut, Jan 14, 2009.

  1. Clear-Cut

    Clear-Cut LawnSite Senior Member
    Posts: 481

    a friend of mine needs this question answered...if you are not positive please to take a guess...also an explanation for the correct answer would be great

    here it is for all of you soil and plant experts

    1. Which of the following elements required by plants does NOT come directly from the soil?

    a. Carbon
    b. nitrogen
    c. magnesium
    d. potassium
    e. iron

    Thank You and Good Luck! :drinkup:
  2. lkc

    lkc LawnSite Member
    Posts: 3

    Just a guess but I am going to go with nitrogen.
  3. greendoctor

    greendoctor LawnSite Fanatic
    Posts: 9,064

    Its nitrogen, all of the other elements only exist in solid form.
  4. 44DCNF

    44DCNF LawnSite Bronze Member
    Posts: 1,460

    It is Carbon. A plant gets it's Carbon from the atmosphere as CO2.
    Last edited: Jan 14, 2009
  5. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Your question is too general, as all of these elements exist in the soil in one form or another. It would be more appropriate to distinguish between a mineral or organic soil, and if these elements are simply contained within the soil, or derived from the parent material.

    If this is for a test, then I would say carbon, and shame on you for not knowing.
  6. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Not necessarily, however that is the primary source.
  7. topsites

    topsites LawnSite Fanatic
    Posts: 21,653

    First off, magnesium, carbon and nitrogen can and do exist both in the soil AND the atmosphere.

    Then, at least potassium bromide and potassium chloride are also found in the atmosphere, and you may not
    believe this but so is iron, and just for kicks sulphur too.

    So any or all of those elements may or may not come directly from the soil, it all depends what kind of
    soil it is and what is in it, all or any of those can and do exist in the soil but the soil could also be depleted...

    And it is possible for instance that atmospheric magnesium and soil-based magnesium are not the same element,
    same with potassium and whether or not this I could not tell you, but I can not answer this question from the data given.
    Last edited: Jan 14, 2009
  8. 44DCNF

    44DCNF LawnSite Bronze Member
    Posts: 1,460

    I am not saying the other elements do not exist in the atmosphere, or that the plant does not take them in from there, and that is not the question. Nor is it asking which element is not in the soil. I have interpreted the question as asking which of those elements is not (maybe here it should say generally) taken up from the soil. I say that is Carbon, as it is most generally taken in from the air. As is Oxygen. Hydrogen is from water along with more oxygen. N, P, S, K, Mg, Ca are taken in from the soil. So, carbon, hydrogen, and oxygen are the elements taken in from the air and water, and the others are generally taken in from the soil.
    If you don't complicate the question, the answer is easy.

    Agreed, the question is vague/misleading, but that is what makes tests fun, eh?
  9. 44DCNF

    44DCNF LawnSite Bronze Member
    Posts: 1,460

    I missed a few words, so to clarify:
    "I have interpreted the question as asking which of those elements (required by plants) is not (maybe here it should say generally) taken in from the soil by the plant.
  10. rcreech

    rcreech Sponsor
    Male, from OHIO
    Posts: 6,056

    This sounds like a question off of a pesticide test. Is that the case?

    The reason I ask is...this is how our questions are here in OH!

    They are somewhat tricky!

    I am pretty sure of the answer but sometime it is best to use the process of elimination... so all come FROM the soil except for C.

    I am very positive that it is C as all the others do come directly from the soil.

    Carbon, Hydrogen and Oxygen are 3 of the 16 essential elements needed by the plant to survive but is not considered as soil nutrients.

    I guess I have never put down a hydrogen or oxygen applcation...although I do think an oxygen application could be quite profitable! :laugh:
    Last edited: Jan 14, 2009

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