Why fertlize when test is high?

Discussion in 'Pesticide & Herbicide Application' started by meomypete, Feb 3, 2009.

  1. meomypete

    meomypete LawnSite Member
    from TX
    Messages: 19

    I see very little on this site about not fertilizing when soil test show not to. I've found that the P and K on most existing lawns show > 30 ppm for P and > 250 ppm for K. Seem to me that most think of feeding the lawn NPK rather than making sure that the soil and application meets the needs of the plants on the property without a lot of waste. Is it more of a selling thing rather than anything scientific.

    In farming we go very much beyond what is needed for the healthy appearance of plants. We go into an hidden area that landscape fertilization would not even need be concerned with...for yield rather than appearance. I wonder if anyone even knows the soil's weight in 1000 square feet of soil 7" deep to figure what is needed.
  2. Stillwater

    Stillwater LawnSite Platinum Member
    Messages: 4,889

    No offense but this is a completely ******** post, You found on most lawns the PK shows 30ppm and 250? since when? Where?

    Exactly who is applying amendments when they have values like that? and how do you know this? You do not see discussion in this direction for obvious reasons. But mostly I want to know how you determined that most lawns have balanced values and exactly what is their to discuss when your annulus dictates no action necessary? Exactly what kind of posting would you like to read. your last sentence almost made me soil myself laughing...
  3. LushGreenLawn

    LushGreenLawn LawnSite Silver Member
    Messages: 2,120

    Your post did not mention nitrogen. When my soil test determine that PK levels are ok, which in my area is usually the case. I apply a 24-5-5, or straight nitrogen.
  4. grassman177

    grassman177 LawnSite Fanatic
    Messages: 9,795

    we know this so we only put down higher levels of p-k when seeding and around that time to help boost root growth . i think that is why they offer so many fertilizers at distributors without much p and k, they are doing their part in the equation.
  5. Ric

    Ric LawnSite Fanatic
    Messages: 11,969


    What is in the soil and what might be available to the plant can be two different values. Tissue samples might be a better indicator on available nutrients. Also consider the economics of food production on sq miles compared to sq ft of homeowner turf. The cost of a soil sample might be more than the cost of a little extra fertilizer. I admit the only time I pull a soil sample is when I see a problem. Now I work exclusively on coastal calcareous sand with low CEC. I find spoon feeding slow release complete products gives me the best response. This practice is not viable on large agricultural operations.
  6. muddstopper

    muddstopper LawnSite Silver Member
    Messages: 2,341

    I havent ever seen 30ppm P, in my area more like 8ppm, and 30ppm is still considered low, and 250ppm K is meaningless depending on the CEC. When you do the math of 780milliequviants for K and a CEC of 14 and want a base saturation of 5%, you might find you might have to add a lot of K to provide any to the plants. (I didnt do the math). Whats your magnessium levels. If the soil test says dont add fert, why add fert?

    Ric is right, if you are feeding the plant, do a leaf analysis.

    Soil is considered to weigh 2million lbs for 6.75 inches depth ( some say 6inches, some say seven inches) per acre. An acre is 43560sqft. You do the math. The real question is how much of that 7inch layer can you influence during the growing season with your fertilizer application. Most likely not the entire 7inch layer. Also consider that the roots of the deepest growing plants, (including trees) take about 95% of all their nutrient needs from the top 4 inches of the soil and about 8 inches is about the maximum depth for areobic biology. Deeper in some soils maybe, but usually less. Fertilizer apps for 7inch soil layers usually results in more nutrient runoff and not more available to the plant. Split application usually provide more benefits than one large application because of less nutrient loss due to runoff. This is the same for a field crop as it would be for a landscape.

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