Skip Navigation

Just Say "NO!" to Tillage

By: Dan Gillespie, No-Till Farmer and USDA Natural Resources Conservation Service Soil Conservation Technician

Spring planting appears to be right around the corner with geese flying overhead and robins looking for earthworms in the lawn.  The soil moisture profile is in great shape thanks to the wet snowfalls we have been receiving through the winter. 

Mother Nature has been at work already in our fields, doing her “tillage” with repeated freezing and thawing in the top two to six inches of soil.  The repeated wetting and drying out of the topsoil is also expanding and contracting the soil and providing another “tillage effect” as soil swells and dries.

THE SOIL IS LIKE A BIG LUNG

The net effect of all these shrink and swell processes is the formation of spaces between the soil aggregates called soil pores.  Soil pores are the respiratory system of the soil, allowing needed air to get to plant roots as the soil dries out and the moisture is replaced with air.  We can equate this to “breathing in” or inhaling by the soil.

On the flip side, after the soil profile has either dried out from plants using the soil moisture to grow, or gravity has pulled the moisture down deeper past the root zones, we now have room in the soil for rainfall or irrigation water to infiltrate.  As water is pulled by gravity into these open pore spaces, the air rises and “expires” into the atmosphere.  We can equate this to exhaling by the soil. 

These pore spaces, the earthworm burrows, and the channels resulting from dead and desiccating roots are the macropore system that Mother Nature designed and has maintained for thousands of years.  Protecting the structure of these pore spaces should be our goal.

THE CULPRIT IS TILLAGE

Tillage is a catastrophic event for the soil!  As the curved shares of the plow, the conical blades of the disc, or flat sweeps of a field cultivator contact the soil, the pressures exerted to invert the soil or turn those disk blades are the same pressures that crush soil aggregates and destroy the soil pores.  The blades of these implements shear the soil to invert it, and can create horizontal areas of compaction called “plow pans” in the soil profile, especially if the tillage event occurs when the soil is wet.

Another result of Mother Nature’s eons of no tillage was the building of soil organic matter to levels as high as six or seven percent or more in our prairie soils.  After breaking up the prairie just a little over a hundred years ago, we have already reduced the soil organic matter to as low as one percent in some cases.

SEE WHY WE SHOULD SAY “NO!” TO TILLAGE

The natural model we need to aspire to is usually right next to the field, in a road ditch or shelterbelt.  Take a spade and dig up a clump of soil one spade width and one spade depth and set it on your tailgate.  Then walk out into your field and take the same sample from one of your eroded hillsides.

Set the samples side by side and look for differences.  The first notable aspect will likely be the color of the soil.  The undisturbed ditch soils will have a darker color, indicating a higher soil organic matter content.  Also note the size of the soil particles, as soil organic matter components will act as a soil glue to hold the soil particles together in larger aggregates.  The larger the aggregates the more volume is represented in pore space.

Grab the tilled soil sample with both hands and wiggle gently try to pull the soil apart from top to bottom.  Observe if the sample fractures horizontally somewhere between the two to eight inch deep level, or sometimes multiple times.   These fractures can expose plow pans from different implements, ranging from sweep to disk blade to plow depths.

Grab the “Mother Nature’s best” sample in the same way and wiggle gently in the same way.  The larger aggregates will have a blocky structure and separate more in a spiral from top to bottom.  You can look at the soil and easily see that water would move into the soil profile faster.

Here's a great example of soil that was no-tilled for 11 years (on left) and soil that has been tilled. The no-tilled soil has better structure and more organic matter. The soil on the right looks depleted and lacks structure. You can see which one would have better water holding/infiltration capacity.

Your local USDA Natural Resources Conservation Service office has a Soil Quality Test Bucket of tools they can bring out to your farm to help you examine and explore your own soils to see how your farming systems have affected your soils.  Give them a call and let them show you with your own eyes.