Infiltration test

Stan Boyd of South Dakota NRCS made a great little video about doing a simple, single-ring infiltration test on three different types of management. "[Infiltration] responds very rapidly to changes in management."

Single-ring infiltration tests are an excellent way to observe soil porosity and aggregation. Single-ring means one ring, but  because of variability in soil surface and macropores it is much better to time several rings concurrently in a small area.

In order to have a better repeatable observation, we recommend using four or five, 6-inch diameter rings, and running them concurrently using one stopwatch: start #1 at 0, #2 at 1:00 (one minute), #3 at 2:00, and so on, and subtracting the start time from the finish time for each ring. Variability may be high, so 4 or 5 rings will give you a better picture than one. If you are part of a soilhealth.app project, you can use the infiltration data form there which also has multiple recording stopwatches, and can geolocate your observations.

see also

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052494.pdf

NEW in 2020! We now sell stainless steel infiltration rings, fairly rugged but thin enough to keep sharp to cut through roots and soil with minimal disturbance. (Thick rings, when pounded in, tend to collapse macropores.) These rings come in two slightly different sizes so that they nest in pairs, enabling you to carry 4 rings in a single 5-gallon bucket. Order here: soilcarboncoalition.org/infiltration-rings

The full kit should consist of 4 or 5 rings plus:

1. 5-gallon bucket with lid for carrying water and rings
2. 45-oz deadblow hammer (we use Estwing)
3. wood blocks with at least one flat side, multiple because they break, for driving rings halfway into soil
4. flat file (keep the sharp edge sharp!!)
5. 15-oz measure for water (tapered Bumblebee salmon can works well)
6. plastic bag or wrap for protecting soil against fall of water
7. sharpshooter shovel for excavating rings after use (good observation opportunity for soil structure, compaction, platiness, plow pans, roots, etc.)

NOTES on USE: Our 18-ga stainless-steel rings are designed for basic ruggedness and minimal soil disturbance when driving into the soil.

1. Driving: Always use a wooden block (carry spares) when driving these rings halfway into the soil, with the flat side of the wood making good contact with the unsharpened end of the ring. We prefer 45-oz deadblow hammers. Drive the ring straight, do not rock back and forth. If the ring tilts sharply while driving, you've hit a rock or other solid object. On heavy litter, mulch, or sodbound surfaces, even a sharp ring may bounce instead of penetrating. Get it started with heavy blows, and if that fails you may need to cut the sod with a knife, using the ring as a guide, before driving it in.
2. Check the fit between the inner wall of the ring and the soil surface with your fingertips. If there is a crack, tamp it with your fingertips, while avoiding disturbance to the majority of the soil surface in the ring. Especially where the soil is bare, use plastic to protect the soil against the fall of water, and gently tug it away to start your timing.
3. End the timing when half the soil surface is exposed. This allows for consistency where the surface is uneven, and you may need to poke beneath litter to check how much soil surface is exposed.
4. Keep the sharp edge sharp with a file. If you don't, you'll create unwanted soil disturbance and you'll have trouble cutting through roots and litter.
5. When excavating a ring with a shovel, it will be possible to bend the ring by applying pressure too close to the ring, especially where soil is firm. Make sure your shovel blade is well beneath the ring before lifting up.
6. If rings become bent or distorted, you can reshape them on anvil, suitable diameter rugged steel pipe, etc. If you bend the sharp edge on a rock, be sure to straighten it again before re-use.

For some more tips and instructions, see also our Guide:

soilcarboncoalition.org/files/guide.pdf#page=83