Preparing Soil Samples in Rodale Institute’s Lab


By Jesse Barrett – Rodale Institute, Organic Allentown Program Manager

After assisting Rodale Institute Research Technicians, Tara Caton and Emily Lesher, with collecting the zero to twenty centimeter soil samples from our FST (Farming Systems Trial) fields, I was left wondering how the soil samples were prepared for analysis. Tara and Emily are responsible for processing the thousands of soil samples collected from various fields from around our farm over the growing season. They both took some time from their lab work to explain the process to me. The procedure relies on drying the samples, sieving them, and then sent out to a Penn State Extension laboratory for further analysis.

photo-nov-07-2-58-47-pmThe soil samples taken from our FST fields were transported to our Rodale Institute lab and were prepared for the first step in the analysis, drying. Before the whole samples are dried, a five gram subsample is taken. These smaller subsamples are placed in an oven dryer at 105 degrees Celsius for a period of twenty-four hours. It is important not to over dry the samples, as this can have a negative affect concerning their chemical analysis. The oven expedites the process of drying from the “field wet” samples to a state of “true dry” samples.

The drying process for the whole soil samples is a separate procedure entirely. This process allow for researchers to measure the soil’s ability to retain moisture. The whole, larger samples are laid out on examination trays and allowed to air dry over a period of five days. Larger clumps of soil are also broken up in order to ensure an efficient and even drying process.
After the soil samples have been efficiently dried, their total dry weight is recorded.

photo-nov-07-2-58-05-pmUpon completion of the drying process, the soil samples are ready to be sieved. For the zero to twenty centimeter surface samples, the research technicians utilize a two millimeter sieve, meaning the apertures of the sieve grating are two millimeters in size. Sieving the soil samples ensures the researches ability to separate rock from actual soil contained in the sample. The dried, sieved soil sample is packaged and ready to be sent out for final chemical analysis.

Over the thirty-six years of Rodale Institute’s FST experiment, our researchers have learned that crops grown with organic agriculture methods help build our soil health by adding organic matter to the soil, and improve our soils’ ability to retain water as compared to conventional methods of agriculture.

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The tedious, albeit important, task of soil sampling is the only true way to ascertain the true health of a grower’s soil. Rodale Institute’s staff is committed to studying the positive affect that organic agriculture has on our soils’ health, and sharing the data with organic growers nationally and globally. Our research will continue to support our mission; through organic leadership we improve the health and well-being of people and the planet.

For a more in depth description of Rodale Institute’s Farming System Trial, visit rodaleinstitute.org/our-work/farming-systems-trial/.

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