Scientific Method 

applied to agriculture

In agriculture, stratified soils is defined as the uneven level of nutrients at various depths within the soil profile. This is a major problem for farmers and it’s getting worse…

“After taking numerous 8-inch core soil samples on my farm and separating them into 1-inch increments, I discovered I was dealing with a significant stratification problem! Ultimately, this helped me learn that nearly 50% (very high levels) of the P&K resided in the top 2 inches of the soil profile. In contrast, the bottom 2 inches of the 8-inch sample showed very low levels of P&K! This is a significant problem considering most roots grow down, not up.

Follow along with the video below to see precisely how I collect soil samples at my farm to test for nutrient stratification.

Below for download, you can access my soil sample data and my instructions for properly collecting soil samples for lab analysis. I encourage you to try this on your farm to determine if you also have nutrient stratification problems.”

-Marion Calmer

soil nutrient stratification results illinois

What Lead to this Process

P&K Profitability 

10 year study

Over three years, spending $250 on P&K to grow $521 worth of grain.

Profit results of $271 or 108% return on investment of input costs.


economic effects of P&K fertilizer

Here are the three year charts for phosphorous stratifiction testing results.  We’re trying to get a sense of, and determin the optimum levels of the phosphorous as it travels or as concentrations change from surface application.  Do the soil concentration levels hinder optimum growth, and can the cost of deep rip application be covered by the extra grain we grow.

economic effects of P&K fertilizer

Looking in detail at three years of Potassium concentrations in soils tested at the Calmer Research Farms.  $750, $900, and $1000 worth of potassium applied in the differing years as testing continues until we find the tipping point, or the sweet spot.

economic effects of P&K fertilizer

Here we are presenting the results of the Phosphorous levels tested before and after moldboard plowing our test plot.  Over the span of 13 years, $1000 worth of Phosphorous has been applied, and the concentration gradient is apparent in the chart on the left transitioning from 142 #/acre down to 37 #/acre @ 8″ deep.

In the chart on the right, we have been able to hasten the spread of Phosphorous down to the 2-4″ depths with the ploughing, and split the concentrations throughout by about 75% at the surface, and doubling the concentration at 6″ with little effect below the 6″ mark.

economic effects of P&K fertilizer

The potassium stratification results are a little more balanced all the way down to 7″ deep as seen in the chart on the right.  We have been able to reduce the surface concentration of Potassium by 2/3 or and heighten the concentrations in the 3″-6″ deep zones effectively with the plough.

economic effects of P&K fertilizer

Nutrient Stratification Study

Get the Instructions and Data


Sign up below to receive Marion’s stratification data, instructions for collecting soil samples at your farm, and useful harvesting tips.

How to Test Your Soil for Stratification

Supplies Needed:

    1.  Eight soil sample bags
    2.  8-inch soil probe
    3.  Tape measure
    4.  Knife or cutting tool
    5.  Blender (optional)

Testing Process

  1. 1. Label soil bags with the appropriate depth of the enclosed soil sample. Since there will be eight bags for the 8-inch core sample, label the bags as follows:
    a. 0”-1” b. 1”-2” c. 2”-3” d. 3”-4” e. 4”-5” f. 5”-6” g. 6”-7” h. 7”-8”
  2. Using an 8-inch soil probe, insert it into the ground to obtain the first 8-inch core soil sample.
  3. Place the soil probe on a flat surface and open the “mouth” of the probe so that the core sample is visible.
  4. Place a tape measure next to the soil probe to measure each inch of the core sample.
  5. While referencing the tape measure, use a knife or cutting tool to slice the 8-inch core sample into 8, 1-inch increments.
  6. Place each inch-long piece of the core sample into the appropriately labeled soil bags. Note: The top 0”-1” sample will be at the top of the soil probe, closest to the probe hinge. The bottom 7”-8” sample will be the piece closest to the bottom end of the soil probe.
  7. Repeat steps 2-6 approximately 20 times until there is a sufficient sample in each bag.
  8. Leave bags open to air dry for two days.
  9. If desired, mix the contents from each bag individually in a blender, then place the contents back into the respective bag. (ONLY MIX ONE BAG AT A TIME!)
  10. Label soil bags with your information and submit them to a lab of your choice for testing.

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