Aggregate Stability Demonstration
In healthy soil, particles bind together to form stable aggregates that resist breakage when subjected to tillage, intense rain, or other disturbances. The aggregates can range in size from clumps to gritty sand to microscopic clay particles. Soil aggregates are important because they protect the organic matter within their structure from decaying due to attack from soil micro-organisms.  Organic matter, in turn, is important because it helps soil hold water, and therefore, decreases the amount of run-off from fields. Organic matter also improves aeration (the amount of air in the soil), especially on finer textured soils such as clay.

The jar on the left is from a field where most of the topsoil has eroded. The middle jar is from a field that has been in continuous no-till for 11 years. The jar on the right contains the same soil type as the no-till jar, but the soil came from a conventionally tilled field.
 
Required Materials:

 

  • Clod of soil from a field that has been no-tilled for several years

  • Clod of soil from a conventionally tilled field.

  • Clod of degraded soil from a severely eroded field

  • 3 wide-mouthed jars filled with clean water
Directions:
  • Air dry the soil clods.
     
  • Gently drop clods in containers of clean water.
     
  • Swirl the water in each container.
     
  • Repeat the procedure with the clod of degraded soil.

Results:

 

Note that the clod from the no-tilled field stays together and the water remains fairly clear. The clod from the conventionally tilled field, however, starts to dissipate and the water becomes somewhat cloudy. The jar containing the degraded soil demonstrates the effect that an intense rainstorm has on an agricultural field.

      Clearly, the continuous no-till soil particles hold soil together much better, making the soil more resistant to the erosion process.

 

Know Your Watershed Coordinator