TO MEASURE IS TO IMPROVE
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
14 years of nutrient data shows that a majority of nutrients reside in the top 2 inches of the soil profile.
What Lead to this Process
P&K study
Marion has been studying the effectiveness of surface-applied dry P&K fertilizer for more than a decade. Over the past three years, he has been studying the profitability of surface-applied P&K. Throughout those three years, Marion applied $250 worth of P&K to grow $521 worth of grain. That’s a profit of $271 or 108% return on investment over input costs! Next, Marion took 8-inch core soil samples to determine nutrient levels at an inch-by-inch level. The results were alarming!
Three different soil tests taken at an inch-by-inch level showed the majority of Phosphorus nutrients in the top two inches of the soil profile. In contrast, the bottom two inches of the core sample contained very low Phosphorus levels. Because these were no-till fields, it was obvious the nutrients weren’t sufficiently traveling deeper into the soil profile. This was a problem considering most roots grow down not up!
The 8-inch core sample showed similar results with Potassium levels. Like the Phosphorus data, majority of Potassium nutrients resided in the top 2 inches of the soil profile and struggled to move further down into the profile.
Here we are presenting the results of the Phosphorous levels tested before and after moldboard plowing the test plot. Over the span of 13 years, $1,000 worth of Phosphorous and Potassium has been applied, and the reduction of nutrient concentration is apparent in the chart on the left, transitioning from 142 #/AC down to 37 #/AC @ 8″ deep.
The chart on the right shows data from the same field after moldboard plowing. By turning over the soil through tillage, the concentration of nutrients has been more evenly spread throughout the soil profile.
The soil test results also showed the uneven level of Potassium within the top 2 inches compared to the rest of the core sample. Similar to the before and after tillage results for the Phosphorus tests, Potassium levels were also more evenly distributed after moldboard plowing the test plot. Through tillage, the surface concentration of Potassium was reduced by 2/3, and the concentration of K in the 3″-6″ zones increased.
Nutrient Stratification Study
Get the Instructions and Data
RESULTS Directly to YOUR EMAIL
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:
- Eight soil sample bags
- 8-inch soil probe
- Tape measure
- Knife or cutting tool
- Blender (optional)
Testing Process
- 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” - Using an 8-inch soil probe, insert it into the ground to obtain the first 8-inch core soil sample.
- Place the soil probe on a flat surface and open the “mouth” of the probe so that the core sample is visible.
- Place a tape measure next to the soil probe to measure each inch of the core sample.
- While referencing the tape measure, use a knife or cutting tool to slice the 8-inch core sample into 8, 1-inch increments.
- 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.
- Repeat steps 2-6 approximately 20 times until there is a sufficient sample in each bag.
- Leave bags open to air dry for two days.
- 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!)
- Label soil bags with your information and submit them to a lab of your choice for testing.
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Research Results PDF EMAILED to you:
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