Phosphorus 11 lb/Acre

Discussion in 'Pesticide & Herbicide Application' started by ThreeWide, Mar 25, 2005.

  1. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    Had a few soil tests for my clients where Phosphorus was in the 11 lb/Acre range. They all have existing Tifway 419 that has not performed well. The root systems appear very shallow and fragile. I'd like to get this corrected, so here is my question.

    Using 18-46-0 Diammonium Phosphate, what would be the maximum to apply in a single application? If I examine my proposed nutrient schedule for 2005, 1 lb of P per 1,000 with this application wouldn't be enough. The N would also fall short in that application.

    If I could do 2 lbs of P per 1,000 for this single application, that would balance everything out by the end of the year. Subsequent applications in 2005 will have only minimal amounts of P.

    We have clay soils if that factors into the equation.
  2. since p is pretty imobile, I would do several applications, and use a very small particle size fert!
  3. LonniesLawns

    LonniesLawns LawnSite Senior Member
    from KS
    Posts: 317

    I have personally never had a soil test doen in my hundred of test that showed low phos. - but ther are some things that coem to mind to consider when adding phos.

    One as, Tim said, it is very mobile in the soi. Applying along with aeration can be helpful. Not sure that this would be practical for all of your accounts though,

    Also, Acid soils are favorable chemical environments for reactions that fix phosphorus, making it unavailable to plants. So get your ph on the lower side if this is common to your soils.

    Also, Mycorrhizae are a group of naturally occurring fungi that infect roots, increasing the nutrient-absorbing capabilities of the host plant. This is especially important for phos in turf.

    Specific to DAP - I have never seen it applied at 2#P rate -- DAP can be very acidic and that much could be very harmful to plants -- I would assume - since again - I have no experience with this rate. It has a alt index of 0.64 - so that in itself would say it could be applied at a higher rate.

    DAP always seems to have a large granule size as well. MAP and superphosphate have smaller granule sizes and that can be important for incorporation into the soils.

    Whats your typical CEC? With clay soils it sghould be high -- in the 20's? This will make the addiiton of P even more troublesome.

    Overall I would say correcting phos defficiencies is a multi year project -- but very important for the health of your lawns.
  4. kipcom

    kipcom LawnSite Senior Member
    from indiana
    Posts: 352

    Are their any "worms" in the soil ???
  5. Runner

    Runner LawnSite Fanatic
    Posts: 13,494

    I would turn your fert. around. There are ferts that would be MUCH more beneficial than what you are describing you are using. The beauty of it is, you are entering a prime time for these to REALLY have an immediate visible effect. I would go down on the P and put a super boost on the potassium. You will grow a root system and turf so dense that you will have trouble mowing it. It will have greater trigger pressure, too. What this is, is "bounce" or stiffness. Stay off of the heavy N contents too at this time of year. We do everything backwards. While many homeowners are being duped by companies that "zap" their lawn into a "quick green", they are also having to deal with excessive topgrowth. We go easy on the N, and build a hardy thick base with deep root systems. This way, it is much more drought tolerant and disease tolerant during the hot months, since it has built itself that way early in the season while the root establishment time is right. Like I say, it's backwards to what alot of other companies do, and to what is being sold to people who buy their own. Those programs are just top general of an instant appearance thing, rather than a long term health thing. I guess we use more of a golf course mentality. I'm sure Tim can relate to this line of thinking......
    I hope this helps.
  6. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    I totally understand what you are saying here. However, you must remember that I'm dealing with warm season turf. Spring rains here do not cause flush growth as what you see up North with Bluegrass. We see more flush growth problems in the Summer when the soil temps are high. It also needs a lot of N.

    The remainder of my program consists of applications such as 25-2-5, 32-5-12, and 21-0-21 depending on the particular situation and soil condition.

    They will all get their needed supply of K as the season goes on.
  7. Runner

    Runner LawnSite Fanatic
    Posts: 13,494

    So your grasses don't grow faster in the following weeks that they come out of dormancy? Ours does,..that for sure! lol I don't know much about warm season grasses, but I'm always intrigued and interested when I learn something new on here about them.
    Regarding the phos., up here, we are getting farther and farther from it. Especially in the region that I am in (central Michigan), our phos. levels are high, and are slow to move through the soils. Where we use to use 5%, we are using 0%, now in many cases. Aren't most of your soils down there clay? Or in the area that you're in, are they sandier? We have some of both, around here. It's absolutely amazing what 20 miles difference can do.
  8. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    Our warm season grasses wake up slowly. When soil temps are 55-60 they start new shoot growth, but the real growth takes place at 70+. That comes several weeks later.

    In my area, the soil is exclusively clay.

    We see P issues because this area is subject to a lot of new residential development. They strip off the top soil when building these developments, which leaves the landscape less to work with.
  9. Rwise10230

    Rwise10230 LawnSite Member
    Posts: 75


    I'm glad to see another LCO that does it right with soil tests, Good for you and I hope others in our profession follow a similar example.

    I have the same problem here in the Piedmont Region of NC and have incorporated 18-46-0 into my 7 step applications. Further, I use 19-19-19 as my winterizer when others use huge amounts of N (because the N will be stored for early spring green-up they claim....whew). I've got soil tests with the P range from 0 - 8 when it should be from 40-60. Realizing that getting the P boosted to the levels I want is not a one or two application thing, my applications generally are in the fall when overseeding and aerating. If necessary, I will also boost the N content with an application of 46-0-0. Yes, to those that are maximizing their means another trip around the lawn with my prema-green.

    I tell my customers that I treat the soil for the long term health benefits of building a root system and that I don't treat the ego of homeowners that want an immediate growth of green grass. If that is their desire then they need to call one of the national companies or other local companies that use untrained immigrants that are hell bent on getting their route done everyday!
  10. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    Yes indeed. Can't have good turf without the right soil conditions.

    To me, winterizing Bermuda involves applying a good dose of Potassium. It is also nice to have a good shot of Iron in that last application. If you apply too much N late in the season, you are promoting Spring Dead Spot. Moreover, I use UF products so there will always be N ready to release when the microbes are active. The concept of stored N isn't something I worry about.

    More info on the 18-46-0. I talked to one of my vendors who has years of golf course experience on the application rate. His advice was 200 lbs/A as a maximum single application. That would be exactly the rate I need to correct most of the P issues.

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