The first signs of spring are beginning to show in the Great Lakes region. The sun and warm weather are causing the ag industry to stir. At the lab we have seen increased sample volumes indicating the beginning of the 2020 spring soil sampling season.
The fall 2019 soil sampling season began with the sampling of prevent plant acres in June of 2019 and continued into February of 2020! During the mild winter weather, the past few months some of the soil samples collected were of better quality than others. No matter the soil conditions, soil sample collection depth remains one of the leading causes of soil sampling error. Often when soil samples do not trend with historical results, depth is a factor. So how does this impact winter and early spring soil sampling?
When soil is above field capacity and reaching saturation, the soil physical properties change. The excess water acts as a lubricant allowing soil particles to slide past each other much easier. This can lead to a wide range of soil sampling challenges that can vary by soil texture. As a tube soil sample probe is pushed into the soil, the soil can simply move to the side, thus reducing the soil volume in the probe. If the relatively higher fertility surface soil is reduced in relative soil sample volume, the resulting reported soil nutrient values decrease the same as if the sample was taken to deep. If soil from deeper in the profile is displaced, the reported soil nutrient values will increase, the same as taking a sample too shallow. Auger probes are often more impacted by above field capacity soil moisture than tube probes. Auger probes can simply push the soil to the side rather than retain the soil in the sample. All of these situations are denoted by a lower than normal soil sample volume for the given number and depth of individual soil cores.
Soil samples that are collected when the surface of a nearly saturated soil is frozen often also leads to challenges. As a soil probe is pushed into the soil, the frozen surface soil an act as a plug and prevents soil from entering the probe. Soils can be sampled at moisture levels above field capacity, but extra observational care needs to be taken to ensure the proper depth and volume of soil is collected.
Another challenge we see at the lab is soil bag degradation when shipping of saturated soils. If the soil sample is not shipped quickly after sampling, shipping is delayed, samples are poorly packaged allowing for movement, or the boxes are handled roughly in shipment. The bags can rupture, bag labels can come off, gel and felt tip ink can run, and label information can be rubbed off leading to the loss of the sample or sample identification.
While we welcome the arrival of your soil samples at the lab, but we want the resulting data to be useful and make a positive impact in your soil fertility management. It all starts with a good sample. If you can collect a quality sample in these soil conditions, sample on! If not, stop. If it takes a few days of dry weather to get a good sample, not a problem, we will leave the ICP’s lit for you!