Soil sampling the right way means better results


FAYETTEVILLE, Ark. — The calendar still says summer, but ranchers have fall planting on their minds, which means it’s soil sampling time, said Dirk Philipp, assistant professor for the University of Arkansas System Division of Agriculture.

Sampling is important so producers can “check on the soil fertility status on pastures, determine how to correct nutrient imbalances, develop a fertilizer plan for winter annuals or adjust pH in pastures,” he said.

However, obtaining needed results starts with obtaining good samples.

“Many times soil samples are being incorrectly taken, either too few or in a pattern that does not represent the entire field correctly,” Philipp said. The techniques used to obtain a good soil test are important because soil can be highly variable across a single pasture or field.

Sampling acres and acres of pasture may seem intimidating, but Philipp said subdividing areas to be sampled into “management units,” can make the process more efficient when it comes to determining how much fertilizer or lime is needed.

“These units depend on forage species present, planned stocking rates, class of animals, fertilizer history, previous use: were these sacrifice pastures? Heavy-use areas?” he said.

Once the management units (or pastures) are defined, some easy-to-follow rules apply for taking samples:

• Take at least 15-20 subsamples per pasture/field

• Sampling area should not exceed 20 acres

• It’s best to use a dedicated sampling tool such as a soil probe. These can be mail-ordered and last a lifetime if treated well

When it comes to tools, Philipp said there are different augers/probes are made for different kinds of soil, so select the one most appropriate for your farm.

“Some augers can be connected to a cordless drill to facilitate sampling; this is recommended if many soil samples are to be taken,” he said.

When taking samples:

• Take samples to a depth of 6 inches of possible. Four inches might be OK, but if ground has been worked up, this is too shallow.

• Scrape the duff aside on top of soil to not skew results with organic material

• Walk in a zig-zag pattern across the sampling area to cover the area evenly

• Avoid sampling in areas were watering or feeding occurs, shade areas and along fences, as those have higher nutrient concentrations because of animal congregations and may skew the results

• Collect all 20 samples in a bucket and mix the soil thoroughly

• Fill part of the compound soil sample into a provided box or bag to be shipped to the laboratory

The University of Arkansas Cooperative Extension Service offers soils analyses free of charge, so contact a county extension office for details, he said. There is also a free publication to help interpret the test results. “Understanding the Numbers on Your Soil Test Report,” may be downloaded at www.uaex.edu/Other_Areas/publications/pdf/FSA-2118.pdf.

“Landowners should learn about nutrients and their optimum range in soils, and keep records of those ranges over the years,” Philipp said. “If liming is required, note should be taken that it will take several months before an increase in pH can be measured.”

For more information about managing forages or soils, visit www.uaex.edu, or contact a county extension agent (See list of offices: http://www.uaex.edu/findus/county_offices.htm).