Phosphorus Depletion Zones

Discussion in 'Fertilizer Application' started by Smallaxe, Jul 8, 2013.

  1. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    If it is true that P does not unlock from the mineral soils over time, with the aid of AM Fungi and other microbials, then can it be said that lawns do not require P applications, except as a starter fertilizer for new seed???

    The following article states:
    ... AM fungi grow extensively in soil to form a well-developed hyphal network that absorbs Pi (via fungal high-affinity PiTs) from up to several centimeters from the root surface and can markedly extend the depletion zone (Fig. 1). P is translocated rapidly to the roots (probably as polyphosphate), overcoming the slow diffusion that occurs in the soil solution. The individual fungal hyphae have much smaller diameters than roots, allowing access to narrower soil pores and hence increasing the soil volume explored (Drew et al., 2003; Smith and Read, 2008; Schnepf et al., 2011). These factors are the major cause of increased P uptake and positive AM growth responses. ..."

    So the point here is that the AM Fungi is out there actively getting 'available P' from the soil more efficiently than simple root hairs can... All this amounts to,, is that the AM Fungi can more thoroughly deplete the depletion zone of the available P... There is doubt that AM Fungi can actually retrieve some of the 'unavailable P' that is also unavailable to root hairs alone...

    Is there a legitimate reason for gov't to 'outlaw' P for lawns stating that the lawns don't need it, anyways???
  2. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Let me rephrase it then,,, Would it not be advisable to apply 12-12-12 garden fertilizer to the lawn for the Late Summer App???
    Why or why not...
  3. turfmd101

    turfmd101 LawnSite Bronze Member
    Messages: 1,376

    Hey Axe, I would use a 4-12-12 if available 50%SCU w/full minor or a 14-14-14 100%SCU w/full minor. Each with 50% bio-solids. I believe these would relieve stress and boost cell structure.
    Last edited: Jul 9, 2013
  4. ted putnam

    ted putnam LawnSite Platinum Member
    Messages: 4,732

    I'm no soil biologist but I will say this. There has been a Phosphorus ban in NW Arkansas the last 4-5 yrs ( Huge Lawsuit brought about the ban) This has made professional quality blends that include P very difficult to come by especially at a reasonable price. I am using a blend this year that has 3% P. My lawns look better than they have in yrs. Levels of N and K are about the same as they have always been. Just a personal observation....
  5. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    The Cation exchange in a soil test is also a factor in the availability of phosphorus being able to be absorbed by and local plants.

    In Illinois, Commercial applicators are banned from applying any phosphorus unless a soil sample shows the soil to be deficient. Then an applicator is legal to apply.

    Even if you apply a 12-12-12 fertilizer, only a fraction of the phosphorus will be available for plants to uptake.

    If only 25% of the P is available, the other 75% then creates P loading in the environment. If it's a synthetic source, then everyone wants to put a stop to it.

    If you want results, just apply natural Urea, along with iron and call it a day.

  6. turfmd101

    turfmd101 LawnSite Bronze Member
    Messages: 1,376

    The above blends would be helpful for stressful times of the year. I feel that if we were able to apply our usual blends as in the past of 4-1-2's for those who prefer or require N and 1-2-4's for those who prefer or require K. Our ability to maintain a stronger stand of turf and minimize pest damage would be optimized with economic success. Just an opinion. By the way I believe P is a necessary and not our preference. Its not our choice. Its a plants requirement!
    Last edited: Jul 10, 2013
  7. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,086

    Synthetic P source? All P fertilizers are made with phosphates mined from the ground. P ferts are the least "synthetic" of all the synthetic fertilizers.

    BTW, urea is a synthetic fertilizer, made using the Haber-Bosch process.
  8. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    So P is already in the ground,,, somewhere in concentrated form of phosphates,,, we take it out of the ground and redistribute it to other ground that doesn't have enough to support vigorous healthy growth in any given area...
    I don't see a problem there,,, environmentally or otherwise...

    How about P cycling, back into the turf when mulch mowing??? Tree leaves of loaded with P,,, so would mulching maple leaves into the turf every Fall,,, like Michigan State does, cycle 100% of the P that was available to the plants once b4? or does it become bound up again once it breaks down to compost in the soil??
  9. ted putnam

    ted putnam LawnSite Platinum Member
    Messages: 4,732

    Yep. The father of my right hand man was the manager over 2 Phosphate mines in Florida years ago.
  10. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    No good ideas about P cycling from clippings and leaves???

Share This Page