Soil Health Test Bucket
Did you know that K-State Research and Extension Douglas County has a Soil Health Test Bucket available to Rent for FREE? This bucket is full of some rather odd ‘parts’…a couple of plastic cups and screen filters, a 6 inch steel ring, plastic water bottle, a rubber mallet, a piece of 2 x 4. Dull, right?
Insights into Soil Health, however, revealed that basic tests performed with these odd parts are insightful for evaluating some of the most basic parameters of soil health:
- Wet Aggregate Stability,
- Water Infiltration Rate Rainfall simulation
- and more
Instructions are provided for each test, performed in-field, in the Soil Health Test Bucket.
Besides the common ‘Shovel Test’ to observe overall aggregate structure or platy compaction layers, these tests give a bit more insight to help monitor progress of aggregate stability and water infiltration as related to soil organic matter over time.
What is Wet Aggregate Stability and Why does it matter?
Aggregates in the soil are developed by the combination of sugary carbohydrate deposits from plant roots, (aka., plant-root exudates), microbial ‘glues’, decomposition of crop residues, worm castings, microbial necromass (dead bugs) and the humic and fulvic acids derived therefrom. A higher Aggregate stability in the soil reflects high organic matter, increased soil aeration, rapid water infiltration and nutrient cycling through mycorrhizal fungi (think: Microscopic fungi that transports liquid carbons, and other solubilized nutrients into plant tissues).
The Wet Aggregate Stability (WAS) test simply allows one to evaluate the rate of decay of soil particles in water; when a chunk of soil is submerged in water, how long until it dissolves? Or does it dissolve at all? Put onto a broader scale, if a chuck of soil in the WAS test dissolves quickly – this would reflect poor Aggregate Stability across the field, and increased soil erosion into streams.
The Water Infiltration Test also reflects the degree of increased organic matter and aggregates in the soil. A 6-inch steel ring is hammered into the field, with a plastic liner placed over the soil. The equivalent of 1 acre-inch of Water is poured over the plastic liner, and a timer is used to calculate the rate of infiltration of 1 acre-inch of water, once the plastic liner is removed. Fields with low organic matter, increased compaction or poor aggregation, have ‘low’, ‘poor’ or ‘slow’ infiltration, over many minutes, sometimes hours to absorb 1 acre-inch of water. Those fields with high organic matter and great aggregation have high, rapid infiltration rates in a matter of seconds! The higher infiltration rates reflect the ability of the soil to absorb water during a rainfall event. The more rain you get, the more infiltration you want, right?
A soil’s ability to absorb and hold water will increase the plants access to water, increasing crop growth especially during dry spells. Rather than seeing muddy streams of soil washing off the field – or ‘puddling’ across acres after a rain, the soil will absorb the rain, and any runoff will be clear. The beauty of the Water Infiltration test – is in being able to calculate the time it takes to infiltrate 1 acre-inch of rain, then noting the difference observed over time as changes are made to diversify crop rotations, by adapting No-Till practices, and incorporating cover crops for summer or winter grazing, for example.
The Rainfall Simulation test is very similar to the Wet Aggregate Stability Test – in that it helps monitor the ‘run-off’ by applying 1 acre-inch of water to a chunk of soil and observing the difference over time…how much of the soil falls into the cup, or does any at all?
These tests are simple to perform in field, alongside the common ‘shovel test’. Please drop by the Douglas County Extension office if you’d like to borrow the Soil Health Test Bucket or let the Agriculture Agent, Margit Kaltenekker, know if you’d like to have assistance bringing this out for a trial run!