Not a Disturbing Trend

Disturbance of all types — physical, biological and chemical – is gradually being reduced in American agriculture

Editor’s note: This is the second in a series of five explanations of the principles of soil health, as described by Jay Fuhrer, who was one of the first to define these principles as a whole. Each article will include a description of the principle along with a profile of a farm that is successfully implementing it.

Driving through a landscape allows you to observe fields with and without soil disturbance. Physical disturbance or tillage is the easiest to see. Biological soil disturbance — limited photosynthetic time and limited plant diversity, along with chemical soil disturbance or pesticide use — is more difficult to see. 

Let’s look at a few terms we’ve used to describe how we manage soil over the years. These are listed in roughly chronological order, although there is of course much overlap.  

Tillage

Tillage is as old as crop production and is well recorded in historical documents. Now fast forward to the present and ask yourself a simple question: How much soil loss can you tolerate per acre or per bushel you produce? For myself, as a long-time conservationist, the answer is zero. 

The reasons people give for tillage are lengthy, but they usually have little to do with managing wind and water erosion, water quality and quantity, building soil aggregates, or carbon. Early best management practices for erosion control consisted of strip cropping, contour cropping, windbreaks, terraces, diversions and waterways, to name a few. These were attempts to slow soil degradation with narrow fields and structural practices — basically treating symptoms instead of the problem. For example, the government might install a waterway to reduce water erosion, instead of helping farmers improve water infiltration in the drainage area. That said, this was the early start of natural resource conservation. 

Biological disturbance was lower during this period, as we had more plant diversity, perennials and livestock on the landscape. Chemical disturbance was lower during this period, too, but was starting to increase. Overall, soil degradation was significant during this era. 

Conservation tillage

This agricultural term was commonly used for decades. Usually, this effort consisted of tillage implements that left more residue on the soil surface and used less plowing. Field size expanded, and tractor speeds increased. 

Biological disturbance increased due to a loss of plant diversity, perennials and livestock, resulting in less photosynthesis and less plant exudate diversity. Chemical disturbance also increased, with more fertilizer and pesticide use. However, it was a step in the right direction from the viewpoint of emphasizing the importance of conservation. Soil degradation slowed but continued. 

No-till

When no-till was introduced, we started to see a significant drop in erosion and related natural resource concerns. My first monitored soil organic matter gain was recorded in an early 1990s no-till cropping system. More farms soon followed. Thanks to the work of scientists like Dr Dwayne Beck, the retired research manager at Dakota Lakes Research Farm in Pierre, South Dakota, we also started to understand that no-till systems are designed to work with diversified crop rotations. 

While physical disturbance decreased in this time period, biological and chemical disturbance continued to increase. Simplified crop rotations used chemical disturbance to offset limited plant diversity. Conservation was now a partner with the no-till planting concept. While imperfect, this was another step in the right direction. 

Soil health

In the soil health era, dynamic soil properties became important indicators — soil aggregates, infiltration, soil organic matter, water and nutrient holding capacity, and bulk density, to name a few. Plant physiology helped further unravel the carbon cycle. Soil demonstrations like slake, the wind erosion model, and the rainfall simulator were commonplace. 

Again, physical disturbance decreased, but biological disturbance also decreased with the use of cover crops, which restored photosynthesis activity and plant diversity. Chemical disturbance continued to increase, though. Conservation was now a partner with soil health. 

Regeneration

Here today, greenhouse gases (carbon dioxide, methane, and nitrous oxide) are in the forefront. The soil health principles are used to rebuild our soils. Farmers and agronomists are starting to focus on carbon (the food) and are asking whether more carbon is coming into our system than is leaving it, understanding that an overall balance is needed to regenerate or rebuild the soil. 

More emphasis is now placed on nutrient density, both in crop production and in grass-finishing meat. People are realizing that agriculture is an extraction business and are asking what we are willing to do to offset nutrient export. Physical disturbance is decreasing, biological disturbance is improving, and even chemical disturbance is decreasing due to some amount of pesticide reduction.