How to prevent nutrient deficiencies AND use less fertilizer

C62291821dac0dd5b7ef3b72a30cd137?s=47 Micah Woods
January 04, 2017

How to prevent nutrient deficiencies AND use less fertilizer

This is about how much of each nutrient it is reasonable to apply to the grass, how soil testing can be used, how MLSN can be used, and how to make it very simple to apply enough fertilizer to ensure the grass will be supplied with enough. The end result of applying these techniques and the MLSN method will usually be the application of less fertilizer.

C62291821dac0dd5b7ef3b72a30cd137?s=128

Micah Woods

January 04, 2017
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  1. 1.

    How to prevent nutrient deficiencies AND use less fertilizer Micah

    Woods Chief Scientist | Asian Turfgrass Center www.asianturfgrass.com 12 January 2017 Campus del Césped seminar series
  2. 2.

    Four points of discussion 1. Prevent deficiency by ensuring grass

    is supplied with all it can use. 2. Using soil test data. 3. Using the MLSN nutrient guidelines specifically. 4. Results: no deficiency, less fertilizer use. Poa pratensis Japan
  3. 5.

    Cynodon & Stenotaphrum Hawaii The amount the grass can use

    is directly related to the growth rate.
  4. 6.

    For more about this, see: A Short Grammar of Greenkeeping

    https://leanpub.com/short_grammar_of_greenkeeping and Viridescent, the ATC blog www.blog.asianturfgrass.com
  5. 7.

    Grass uses the amount that it grows. More growth =

    more nutrient use. No growth = no nutrient use. Poa Reykjavik
  6. 9.

    We are working with professionally-managed turf. The growth is controlled

    by how much nitrogen is supplied. Agrostis Girona
  7. 10.

    One way to estimate nutrient use is based on the

    quantity of N supplied. Let's say we have an annual rate of 15 g N/m2 and we are growing creeping bentgrass (Agrostis). The expected use of other elements for Agrostis is: Element % in dried leaves ratio, N to element Expected use (g/m2) N 4 1:1 15 K 2 2:1 7.5 P 0.5 8:1 1.9 Ca 0.5 8:1 1.9 Mg 0.2 20:1 0.8
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    Let's say we have an annual rate of 10 g

    N/m2 and we are growing seashore paspalum (Paspalum vaginatum). The expected use of other elements for Paspalum is: Element % in dried leaves ratio, N to element Expected use (g/m2) N 3 1:1 10 K 3 1:1 10 P 0.5 6:1 1.7 Ca 0.5 6:1 1.7 Mg 0.2 15:1 0.8
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    Let's say we have an annual rate of 20 g

    N/m2 and we are growing bermudagrass (Cynodon). The expected use of other elements for Cynodon is: Element % in dried leaves ratio, N to element Expected use (g/m2) N 3 1:1 20 K 2 3:2 13.3 P 0.5 6:1 3.3 Ca 0.5 6:1 3.3 Mg 0.2 15:1 1.3
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    Or, estimate N rate (and the other elements) using the

    temperature-based growth potential (GP).
  11. 14.

    Paspalum vaginatum Las Palmas An example of calculations based on

    temperature – prediction of 12.4 g N/m2
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    Annual N of 12.4 g/m2, grass is Paspalum. The expected

    use of other elements is then: Element % in dried leaves ratio, N to element Expected use (g/m2) N 3 1:1 12.4 K 3 1:1 12.4 P 0.5 6:1 2.1 Ca 0.5 6:1 2.1 Mg 0.2 15:1 0.8
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    Annual N of 22 g/m2, grass is Agrostis. The expected

    use of other elements is then: Element % in dried leaves ratio, N to element Expected use (g/m2) N 4 1:1 22 K 2 2:1 11 P 0.5 8:1 2.8 Ca 0.5 8:1 2.8 Mg 0.2 20:1 1.1
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    Agrostis Minnesota What about micronutrients? I rarely mention them. Why?

    photo by Andrew McDaniel photo by Andrew McDaniel
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    For the Valencia example, all elements. We will use these

    numbers later. Let's call this amount a. Element Expected use (g/m2) N 22 K 11 P 2.8 Ca 2.8 Mg 1.1 S 1.1 Fe 0.06 Mn 0.03 Zn 0.02 Cu 0.02 B 0.01 Mo 0.0003
  20. 26.

    Don't get confused • The purpose of soil tests is

    to determine how much fertilizer to apply. • You already know how much the grass can use. That is the default amount to apply as fertilizer. However, if the soil can supply some (or all) of that required amount, then subtract the amount the soil can supply. • Soil test annually and check if nutrients are going up or down.
  21. 27.

    Soil K is going up. This means more K is

    being applied than the grass is using.
  22. 28.

    Soil K is going down. This means the grass is

    using more K than is being applied.
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    Let's say that for our site in Valencia with Agrostis,

    these are the most recent test results. We will use these numbers later. Let's call this amount c. Element Mehlich 3 soil test (ppm) K 61 P 71 Ca 623 Mg 84
  25. 31.

    Let's develop an equation to express how much fertilizer is

    required to be sure we prevent deficiency. 1. The general expression will be: [amount we need] – [amount present] = [amount to supply as fertilizer] 2. We want to supply the grass with 100% of what it can use. We already discussed that and are calling that amount a. This is part of [amount we need]. 3. The [amount present] is the soil test amount, which we are calling c. 4. If there is no soil testing, then supply a and be done with it. If we want to consider the soil, we need a buffer amount to keep in the soil.
  26. 33.

    The MLSN guidelines are a minimum level that you don't

    want to drop below. These act like a buffer amount of these nutrients in the soil. We'll call this amount b. https://www.paceturf.org/PTRI /Documents/1202_ref.pdf
  27. 35.

    Now we can update the equation to a form we

    can use. 1. The general expression is: [amount we need] – [amount present] = [amount to supply as fertilizer] 2. The [amount we need] is the grass use (a) plus a buffer amount we want to keep as a reserve in the soil. That is the MLSN guideline (b). And the amount present is the soil test (c). 3. The equation we can use is: [grass use + MLSN guideline] – [soil test] = [fertilizer requirement] or a + b – c = F
  28. 36.

    If you don't have Mehlich 3 test results, options include:

    1. Getting Mehlich 3 test results. It's pretty easy. 2. Convert your soil tests to estimated Mehlich 3 values. Google it. 3. Pick your own minimum level that you don't want the soil to drop below, and use that as b. 4. Don't bother with soil testing, and apply the full amount the grass can use, a. 5. Use an entirely different approach.
  29. 37.

    However, if you are applying more than the grass can

    use, or much more than recommended by MLSN calculations, you should step back and ask yourself “Why am I applying more than the grass can use?”
  30. 38.

    Please remember this Please remember this When you add fertilizer,

    you do not simultaneously increase the nutrient holding capacity of the soil. Therefore, if you are adding fertilizers and thinking that through those additions you will be able to increase the nutrient content of the soil in the long term, you are mistaken.
  31. 39.

    Agrostis Valencia Let's go back to Valencia, calculating F for

    the previously given a, b, and c values.
  32. 40.

    Annual N of 22 g/m2, grass is Agrostis. The expected

    use of other elements is then: Element % in dried leaves ratio, N to element Expected use (g/m2) N 4 1:1 22 K 2 2:1 11 P 0.5 8:1 2.8 Ca 0.5 8:1 2.8 Mg 0.2 20:1 1.1
  33. 41.

    Element a b c F K 11 5.5 9.1 7.4

    7.4 g K/m2 P 2.8 3.1 10.6 -4.7 No P fertilizer required Ca 2.8 49.4 93 -40.8 No Ca fertilizer required Mg 1.1 7 12.5 -4.4 No Mg fertilizer required The a's are based on expected use of Agrostis if 22 g N/m2 are applied. The b's are the MLSN guideline, with ppm converted to g/m2 using estimated depth of 10 cm and bulk density of 1.5 g/cm3. Divide ppm by 6.7 to get g/m2 with these same rootzone depth and bulk density assumptions. The c's are median values from the Global Soil Survey, expressed in g/m2 as described above. Use your own soil test results. I use these as an example. I won't worry about micronutrients because the grass use is so small. Add some if it makes you happy. Or don't. It probably won't matter either way, and the cost is negligible.
  34. 44.

    Let's imagine 1,000 Agrostis greens in Barcelona. We'll calculate an

    estimated K fertilizer requirement with these conditions: 1. GP predicts N use of 20.7 g N/m2. For Agrostis, that gives estimated K use of 10.4 g K/m2. I'll let each of the 1,000 greens have an a of 10.4 g K/m2. 2. I'll assume the soil K in the 1,000 greens is distributed as in the K from the Global Soil Survey. 3. I'll then calculate F for each of the 1,000 greens using three different scenarios: a: using the MLSN guideline of 37 ppm K b: not soil testing, applying only the amount the grass uses (a) c: using a conventional SLAN guideline of 117 ppm K
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