Take Care with Soil Sample Handling

Knowing how much nitrogen is in your soil can help you make more accurate decisions for nitrogen application. But, the accuracy of those results is important. One large driver of soil nitrate testing accuracy is the quality of the soil sample and the handling of that sample through testing. Soil nitrates are highly dependent on soil temperature and moisture and false results can be experienced based solely upon handling of soil samples.

360 SOILSCAN is an in-field, real-time soil testing system that allows farmers to get soil nitrate readings in nearly five minutes while in the field. This allows for soil samples to be pulled from the field and tested almost immediately, while the soil is still in its near-natural state.

Conversely, when using remote soil labs, pulling and preserving the soil sample is key for consistent and accurate readings of what’s happening in the field. It is especially important to ensure the soil sample is immediately kept cool and shipped quickly on dry ice to the lab. If the soil sample is warmed – either from sitting in a warm vehicle or waiting a day for delivery to the lab – the warmth can activate microbes to break down ammonium to form nitrate, which could increase the amount of nitrates in the sample compared to what was available in the cool soil in the field.

Comparing impact of soil sample handling and delivery
This difference in testing procedures and soil collection make a difference when it comes to consistency across results between 360 SOILSCAN and traditional labs. To demonstrate the importance of soil collection and handling, I’ve conducted a mini research trial using various testing methods to find true field available nitrate readings. Samples were pulled near Waterloo, Ind., on Thursday May 14 when soil temperature at 4 in. was 49.6°F. The results follow.

Soil nitrate

In this first trial, the results didn’t have great variability. A few things contributed to limited differences in the results. First, the soil samples were homogeneous and pulled from the same area in the field. Additionally, the samples were pulled on a day with cool weather, which may have contributed to limited warming and microbe activity of those samples sent to the lab. We’ll continue to conduct similar trials throughout the season to see how summer temperatures may change the results of field-level versus remote lab testing.

Work with your local agronomist to ensure the soil testing you’re conducting is giving you the most accurate results possible and that your soil sample collection and handling is done right. And, check out the differences between 360 SOILSCAN and in-lab testing with this comparison sheet. Learn more about 360 SOILSCAN and get your questions answered with this related blog post from Josh Messer.