University of Maryland Extension

Fall Soil Sampling

Patricia Hoopes

Soil samples are good for three years for Nutrient Management Plan development. Expired soil sample analyses must be replaced! Use your Nutrient Management Plan (NMP) to quickly determine fields in need of sampling. Look at the “Test Date” column on the “Soil Test Results” page of your NMP. Highlight expired soil sample analysis and work off this sheet for sampling.

There are times when you should re-sample a field prior to sample expiration date. Problem fields may be considered for resampling in an effort to find a solution. Fields with questionable analysis results should be resampled to provide results you feel more confident in using to generate recommendations. Divided fields with different crops or management automatically become different management units and must be re-sampled separately.

There are also times when additional soil sampling is required. Fields with a Phosphorus Fertility Index Value (FIV) of 150 or greater may need an additional test. If P-containing products will be applied to the field, a University of Maryland Phosphorus Management Tool (UM-PMT) study must be completed and the P application written into the NMP prior to application. This study requires a Degree P Saturation (DPS) or Al and Fe reported on the soil analysis and may require a new soil analysis if that was not tested for in the current soil analysis.

Why sample in the fall?

  • The soil isn’t frozen
  • If soil sample analysis results don’t look right, there is time to question the lab or re-test.
  • Fall sampling of both soil and manure allow ample time for NMP development. You are required by law to have your nutrient management plan prior to applying any manure or fertilizer.
  • Some growers tell me they get a discount on fertilizer if they order early.
  • Lime is usually applied in the fall and based on a new soil sample analysis.

Some farmers are concerned about developing a NMP too early. Are you concerned that your crop rotations may change? Multiple recommendations can be written for a field. At planting time you would follow the recommendations for the crop you are planting. Are you concerned that a rental property will be taken from you before the crop season? It is always best to have the recommendations in hand prior to spring planting. Lost property can be noted in an addendum at a later date.

You are always welcome to call the office with any questions or concerns.

Soil Sampling Q&A:

What is the correct way to take a soil sample? A sample carefully taken will be a dependable tool to develop nutrient recommendations. “Soil Sampling Procedures for Nutrient Management” flyers are available at the Extension office or at our nutrient management website at Sample plugs should be taken 8 inches deep. While some labs recommend different sampling depths, we need soil samples taken at a depth of 8 inches for University of Maryland nutrient recommendations. Crop recommendations have been developed using soil samples taken at an 8 inch depth.

Can I take a soil sample after a manure application?  “Sampling after manure or fertilizer application, especially in no-till or pasture situations, will make soil analyses highly variable and usually result in highly inflated soil test numbers. The rule of thumb is to wait 6 months before soil sampling. “(Source: Dr. Frank Coale, Professor, Department of Environmental Science and Technology, UMCP)

Are soil samples needed for pasture fields? ” Yes, soil samples are needed. Essentially, nutrients are being applied in the form of manure from the animals. It is not necessary to generate a nutrient recommendation for pasture if an operator has no intention of applying additional nutrients.” (Source: Louise Lawrence, Office of Resource Conservation, MD Dept. of Agriculture)


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