Getting the biggest bang for your buck out of soil testing starts with a good soil sample, notes Doug Beegle, Penn State University Extension soil fertility specialist. He offers these sampling guidelines:
- Sample uniform areas. While most fields are sampled individually, you might want to subdivide fields if there’s potential for significant differences across them. Examples include fields with significant soil differences, where parts of fields receive manure and other areas don’t, and where there are topographic variations (i.e., sidehills vs. low areas) within fields.
- Collect at least 15-20 cores. “More is better,” he says.
- Sample to uniform depth. Inconsistent sampling depth is one of the biggest sources of error in soil sampling. “This is especially true in no-till and reduced-tillage systems where there’s often significant stratification of nutrients in the soil,” Beegle says.
- Avoid atypical areas or sample them separately. “Odd” areas – dead furrows, old fence rows, lime or manure stacking areas, wet spots, etc. – may be too small to manage separately. Don’t sample them, he advises. One or two cores from these odd areas will contaminate the sample for the rest of the field. If these areas are large enough that you’re able and willing to manage them separately, take separate samples.
- Handle samples carefully. Collect soil cores in a clean bucket to avoid contamination, crumble the sample cores and air-dry the sample. Mix the cores thoroughly and take a sub-sample to fill the mailer you send to the lab.