4 Tips for Fall Soil Sampling

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Sprayer for soil sampling

Soil sampling can provide you with critical information on the fertility status of your soil, including potassium and phosphorus levels. Chris Kluemke, Nutrient Maximizer development specialist, Corteva Agriscience, offers four tips as you dig in to soil sampling this fall.

  1. Wait for moisture. With a lack of rainfall between harvest and soil sampling, the nutrients within the soil will not be recycled at normal rates. Consequently, lower nutrient levels will be reflected in soil samples. Another potential problem with sampling during dry soil conditions is that it is more difficult to control the sampling depth and accomplish proper soil core collection.

    “It’s been pretty dry in some areas this fall,” Kluemke says. “Growers will want to wait for a good inch of rain after harvest to ensure adequate soil moisture prior to taking a soil sample.” 

    This Iowa State University Extension article provides suggestions on soil sampling during dry conditions.
  2. Strive for accuracy and consistency. “Inconsistent soil samples just cause headaches,” Kluemke says. That’s why he recommends finding a person or company that will remain consistent in going back to the same area and ensuring accurate soil depth of 6 to 8 inches when sampling.

    Soil samples should be pulled every four years. “Let’s say that four years ago, we had someone pull a sample at 2 inches,” Kluemke says. “This year, we have someone pull the sample at the correct depth of 6 inches. There’s typically a much higher nutrient load in the topsoil than in the bottom 6 inches, so you’re going to see very skewed results.”

    Ensuring accurate and consistent results in your soil samples will help take the guesswork out of fertilizer recommendations. 
  3. Use a certified lab. There are hundreds of soil testing facilities available for you to use. However, not all laboratories are held to the same standard. You can find certified soil testing labs by visiting your state’s agriculture department website.  

    “If you’re putting in the effort to collect accurate soil samples, you’re going to want to use a quality lab that provides accurate results,” Kluemke says.
  4. Watch for trends. When you receive your soil test results, it’s easy to get lost in the little details. “Don’t take all soil test values as absolute,” Kluemke says. “If you’re taking soil samples regularly and accurately, I encourage you to look for trends that can help inform your nutrient management strategy.”

Reach out to your local Extension service or crop retailer to learn more about soil sampling. 


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