NPK = Fertile?

Discussion in 'Organic Lawn Care' started by Smallaxe, Jun 6, 2012.

  1. Smallaxe

    Smallaxe LawnSite Fanatic
    Posts: 10,080

    If we are starting with general mineralized dirt, such as one might find as subsoil after new construction projects; will adding NPK make this dirt, fertile soil??
     
  2. phasthound

    phasthound LawnSite Platinum Member
    Posts: 4,564

    IMO, adding NPK only in these conditions will feed the plant. That does not mean it makes the soil fertile.
     
  3. Skipster

    Skipster LawnSite Bronze Member
    Posts: 1,074

    So, what does it mean for a soil to be fertile?
     
  4. easy-lift guy

    easy-lift guy LawnSite Gold Member
    Posts: 3,376

    Fertile soil means sufficient amounts of minerals are present to support growth of crops or other green matter. Adding NPK or other minerals should only be needed when not naturally occurring in the soil.
    easy-lift guy
     
  5. Duekster

    Duekster LawnSite Fanatic
    from DFW, TX
    Posts: 7,961

    Go ask Myrtle.
     
  6. Smallaxe

    Smallaxe LawnSite Fanatic
    Posts: 10,080

    If there is clay, in the OM free subsoil, then in theory, the NPK would have CE sites to adsorb to...
    Also in the No-Till theory, the act of roots growing in the dirt adds OM to the soil and concievably adding CEC and water retention/perculation properties as well...

    After a few years of adding NPK, Could one begin to think of the subsoil being fertile topsoil in its own rite???
     
  7. gshannon

    gshannon LawnSite Member
    Posts: 1

    NPK does indeed feed the plant, turf, or crop; but does not feed the soil or build the soil. Understanding soil fertility begins with understanding certain things about soil makeup.

    First, it is important to recognize that fertile soils have the characteristic of high exchange sites. Exchange sites are characterized by the term CEC. This is the abbreviation for Cation Exchange Capacity. Exchange sites have both positive and negative charges. A general rule of thumb is that soils with higher CEC readings are usually more productive than low CEC readings.

    Therefore, have a soil test and observe your CEC's.

    Remember, it is not quite enough to ask do I have enough P or K in the soil.
    You may very well have enough P and K in the soil and yet the P and K are not available. So the real question is do I have P and K available?

    Then of course there is PH. Only when the PH is within acceptable range will other nutrients be available. What this means is you may have high amounts of P and K in the soil and yet very little of each is available. So find out what is the proper ph for your type of turf or crop or plant. If the ph is not where it ought to be it may very well mean that more than 50% of the fertilizer you apply never is used by the plant, or turf, or crop.

    Most soils east of the Mississippi River need liming to keep the ph where it ought to be.

    Next consideration is organic matter. Most soils are deficient of organic matter and if one truly wants fertile soil then one must raise the organic content of the soil.
     

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