The importance of P and K

Discussion in 'Pesticide & Herbicide Application' started by jajwrigh, Apr 6, 2005.

  1. jajwrigh

    jajwrigh LawnSite Bronze Member
    Male, from Martinsville, IN
    Messages: 1,405

    Does anyone put down supplements of either P or K at some point in the season? I am aware that turf around here usually benefits from 4lbs of N, 1lb of P, and 2lbs of K per year. I was considering applying a decent portion of K during my second round in the form of SOP. Are there any restrictions or risks that I should be aware of? Any advice appreciated...
  2. Williams Services

    Williams Services LawnSite Senior Member
    Messages: 269

    I was talking to a Lebanon dealer yesterday or the day before, and he was telling me that their 14-14-14 has slow release K. Most of the yards around here that I've looked at so far have a P bank in them ...
  3. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Messages: 2,697

    What does you soil tests recommend? I rarely use P, there is always enough in the soil around here, according to the tests. K is the second most important element for turf growth. Just keep an eye on ph when using SOP. I've applied SOP on many occasions, up to 1#/k.
  4. jajwrigh

    jajwrigh LawnSite Bronze Member
    Male, from Martinsville, IN
    Messages: 1,405

    Does SOP raise or lower ph? How have you results been thus far when you apply 1lb/per k? I think I will collect soil tests from properties in different areas of town and send them off for analysis. Thanks for the good advice.
  5. Randy J

    Randy J LawnSite Bronze Member
    Messages: 1,124

    Phosphorus (P) is important when establishing turfgrass, as it primarily helps roots get established. The Certified Turfgrass Professional manual says, "Phosphorus is considerably less important than nitrogen, and hastens the growth and maturity of turfgrass seedlings as well as stimulating root growth".
    Potassium increases the turf's tolerance to drought, heat, cold, and wear. Potassium can also stimulate root growth and decrease plant's susceptibility to certain diseases.
    They (Certified Turf Pro) recommends, in the absence of a soil test, a balanced formula such as Williams mentioned, 14-14-14.
  6. Grandview

    Grandview LawnSite Gold Member
    from WI
    Messages: 3,251

    I do not apply any P or K without a soil test, except with combination produts. Otherwise P and K levels can build to excessive levels. Excessive K, above 250 ppm can restrict the uptake of calcium and magnesium. Too much P restricts the uptake of iron. The P level should be maintained around 40-50 ppm. Unless clippings are removed P and K levels will build. Nitrogen is lost and must be applied to maintain acceptable color and growth. The fertilizer I use also has 12% sulfur.
  7. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Messages: 2,697

    SOP lowers the ph. I use ferts with a 5-1-3 or 5-0-3 ratio, along with additional K (SOP) if necessary. My soils are in the 7.8 - 8.5 ph range. It generally takes a couple of seasons to get the ph down to around 6.5.

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