Sustainable Agriculture Literature Review - Boulder County

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Agricultural systems in Boulder County are particularly prone to erosion because of
frequent high winds. Areas in Boulder County where vegetation has been removed, for
example annual cropland, overgrazed areas, and burn areas, are even more exposed
and vulnerable to wind erosion than sheltered lands. 355 Certain farming practices, such
as stubble mulch, reduced tillage, no-tillage, strip cropping, leaving a rough tilled soil
surface, and treatment of exposed areas by re-seeding and planting can help to reduce
the extent of both wind and water erosion on cropping and grazing systems.
Tillage Methods
There are two general types of tilling practices, conventional-till or intensive-till and
conservation-till. Conventional-till plows all residues from the prior harvest into the soil,
as opposed to conservation-till, which leaves at least 30 percent of the crop residue on
the surface undisturbed. No-till leaves all crop residue and does not till at all before
planting the following crop. 356 According to the Conservation Technology Information
Center, in 2008, conservation tillage methods totaled 113,764,677 acres in the U.S.,
intensive-till totaled 101,339,774 acres, while all other tillage methods totaled only
58,983,025 acres. 357
Soil erosion is the main concern with the use of intensive tillage practices. To avoid
erosion, farmers may employ conservation tillage, which is broadly defined as any tillage
method that leaves sufficient crop residue in place to cover the soil surface. 358
The benefits of conservation tillage include: 359
- Reduced wind erosion
- Improved soil moisture management
- Increased carbon sequestration
- Reduced water erosion
- Increased options for multiple cropping
- Improved soil structure
- Weed suppression
- Reduction of the volatilization of organic matter from tillage
The benefits of higher carbon sequestration rates go beyond reducing carbon dioxide
emissions. Higher levels of soil organic carbon (SOC) actually help bind the soil particles
together causing the near surface soil to be more stable and less susceptible to water
erosion. Raindrops can be more erosive than runoff or flowing water because they have
a higher velocity, particularly in arid locations. High levels of SOC are important in areas
where annual precipitation is low and evaporation is high, such as the Great Plains, to
decrease erosion. A study conducted in the Great Plains region, including a site in
Akron, Colorado, concluded that under no-till soil practices, the increase in SOC content
was “partly responsible for the greater aggregate water repellency, stability, and
resistance to raindrops.” 360
No-till is a type of conservation agriculture and is a growing trend according to the
USDA. 361 No-till can be used on almost any crop. Beyond protecting soil from erosion,
increasing water retention, 362 and decreasing energy use, no-till agriculture can also
increase the soil’s ability to absorb carbon, decreasing carbon dioxide in the
atmosphere. 363 No-till practices can also decrease farmer’s fuel costs. The USDA
Natural Resources Conservation Service estimates that a farmer can save 3.5 gallons of
fuel per acre by changing from conventional-till methods to no-till. 364
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