Soil ring sampLER & Soil Sample Rings

*Standard dimension of Soil Sample Rings is 5 cm inner diameter, 5.1 cm height in Soil Ring Sampler Sets if not defined by customer. Outside diameter of these sample rings is 5.4 cm.

•  (Sharp-edged) soil ring (stainless steel) of known volume, e.g 100-200 cm3 (ca. 5 cm diameter, 5.1 or 10 cm height; see soil ring table above / soil ring calculator). 
• Soil ring sampler to gently push / hammer the sample rings into the soil.
• Soil knife, putty knife or similar to remove the soil ring and any excess soil adhering to it.
• Either 2 lids for the soil ring or plastic bags, pot. rubber bands to secure the lids or bag, and marker pen for labeling sample numbers (alternatively, metal soil rings may be numbered permanently).
• Transport box or backpack for equipment and soil samples (in rings or emptied into plastic bags).

Example sampling procedure:

1. Sample (in the vicinity of) your research plots, but avoid any area where soil compaction may have occurred from other sampling activities or where future research is planned. See also brief overview on soil sampling techniques and key references.
2. i) Remove the coarse litter layer and possibly any organic layer and gently insert the first ring directly from the soil surface to sample the 0-5 or 0-10 cm depth layer; if the sampler could not be inserted smoothly (e.g. due to woody roots or stones), try again nearby. ii) Alternatively, excavate a small soil pit with a preferably smooth soil profile wall and then gently insert the soil ring from the side to sample either at defined soil horizons or soil depths. For soil horizons larger than the diameter of your soil ring sampler (e.g. 10-20 and 20-30 cm depth layers), consider placing the centre of the soil rings at 15 and 25 cm depth respectively. For thinner layers, consider coring from the top after removing overlying horizons or use smaller soil sample rings. In any case, it is key to avoid compaction of soil samples during sampling.
3. Excavate the soil from around the sample ring and cut the soil below the base of the ring from the side, e.g. using a pallet knife. Cutting a straight surface at the base of the soil ring is particularly important when using the direct soil ring sampler (type 1) to sample the correct volume, while the cutting shoe of the type 2 or type 3-soil ring corers holds some 'extra soil' which can be removed once the soil ring is removed from the ring corer 'sleeve'.
4. Remove excess soil from above the ring using a knife: first remove excess soil from above the sample, then place a cover/lid over the ring and turn it upside down to remove soil adhering to the ring and cut a smooth surface at the bottom of the ring. Either transport the cleaned ring core to the laboratory (using lids) or remove all soil from the ring into a plastic bag and seal immediately. To stay at field moisture, soil remaining in sample rings should be additionally wrapped in bags, avoiding too much headspace for moisture to condensate on. Cooling is often preferred until processing / soil respiration measurements on undisturbed soil ring cores.

Here are some best practices to consider when planning your soil ring sampling campaign:

• Appropriate soil ring size: The size of the soil ring sampler should be selected based on the soil texture and depth of the sampling site. If the soil has a high rock skeleton content, a larger ring sampler may be required to ensure that the sample is collected intact. Smaller rings may be better suited to sample narrower soil horizons or more detailed depth increments (e.g. 5 cm steps). In general, larger diameter samplers may reduce the degree of sample compression due to the reduced friction on inner ring surfaces. 
• Sample handling: It is important to handle the soil sample carefully to avoid compaction or alteration of the sample. Samples can be carefully removed from the sampler and transferred to a container for transport to the laboratory, or sample rings can be sealed with lids for transport. Make sure the soil rings are 100% filled on top and bottom, do not lose soil belonging to the soil volume sampled while emptying the soil rings! For deeper / shallower soil sampling campaigns, where compression is less of an issue or time is of the essence, a correction factor may be calculated from the height of soil sampled and the depth of the hole in the soil.
• Sampling depth: Soil ring samplers should be inserted into the soil at a consistent depth to ensure samples are representative. Carefully consider the depth of organic topsoil layers when sampling vertically - consider to sample organic and minerals soil layer separately. Often horizontal sampling within the walls of soil pits provides the most representative data on soil density depth profiles. Choose sample rings which fit the dimensions of the morphometric horizons you want to sample. 
• Repeat measurements: To improve the accuracy of bulk density determination, several samples should be taken and measured from the same area. A minimum of three replicates should be sampled per depth / horizon for any interpretation.
• In the lab: determine moisture content, non-fine soil constituents: Soil moisture content has a significant effect on bulk density measurement. It is thus important to determine the soil moisture content in the laboratory (on a subsample immediately when processed, to minimize drying). Similarly, it is important to determine the volume and weight of stones and plant organs in your sample - allowing to determine the fine soil content within the soil ring.

For other tasks, consider large-diameter Soil Corer (deep sampling with often minor compression) or the Topsoil & Root Corer (ideal for humus and root sampling), respectively. See below for a small selection of articles / manuals providing more detailed descriptions on soil sampling procedures.