Conservation Conversation: Environmental benefits of conservation tillage
As strip-till acreage expands, farmers are able to recreate soil and water cycles more closely resembling characteristics of prairies and woodlands before settlers first put plows to the soil.
The residue from the harvested crop is left on the soil surface. This layer of leaves and stems mimics the layer of litter that once covered native soils, protecting the soil from heat, preserving soil moisture and preventing erosion.
Decaying root channels and burrows from earthworms serve as macropores, which aerate the soil and improve water infiltration.
Other attendant benefits, including a return of soil organisms, birds and mammals, also are being realized.
This week’s column will focus on two of the benefits: reduced soil erosion and less sedimentation. Conservation tillage is one of the most practical and economical ways to reduce soil erosion.
Reducing or eliminating tillage operations leaves more crop residue on the soil surface, protecting the soil from the erosive impacts of wind and rain.
Reductions in erosion are proportional to the amount of soil covered by crop residue.
No-till systems, which leave nearly all plant surface residue in place, can reduce erosion by 90 percent or more. There have been dramatic decreases in erosion in the United States since 1982.
There has also been a big decrease in Kleberg County in my 26 years in South Texas. Much of this reduction can be credited to the adoption of conservation tillage by farmers.
Sheet and rill (water) erosion on cultivated cropland fell from an average 4.4 tons per acre per year in the early 1980s to 3.1 tons per acre per year in 1997, a 30 percent decrease. There has been even more of a decrease since that time. Average wind erosion rate dropped 31 percent.
Almost one billion tons per year of soil savings have occurred due to these changes in management. However, erosion is still occurring at a rate of 1.9 billion tons per year, and 108 million acres (29 percent of cropland) is still eroding at excessive rates.
A 1998 National Water Quality Inventory reports that sedimentation is the most prevalent pollutant in streams that have been identified as environmentally impaired. Unacceptable levels of sediment occur in 40 percent of impaired stream miles.
Bacteria was the second most prevalent pollutant present in 38 percent of impaired miles, followed by nutrients, occurring in 30 percent of impaired miles. Conservation tillage reduces the runoff of all these pollutants to surface water systems. Tons and tons of sediment have been kept out of Baffin Bay in Kleberg County due to high residue farming such as strip-till.
Sediment decreases the storage capacity of reservoirs and interferes with the navigational and recreational uses of water. According to a U.S. Department of Agriculture study, the annual cost of damage to water quality from sediment originating on farmers’ fields was $4 billion to $5 billion in the mid-1980s.
Damage values were calculated considering the cost of maintenance due to erosion, such as dredging rivers, cleaning road ditches and treating drinking water, as well as economic losses.
As mentioned above, soil erosion rates fell 30 percent between 1982 and 1997, largely due to the adoption of conservation tillage by U.S. farmers and land enrolled in the Conservation Reserve Program (CRP).
The offsite erosion damage ($8.78 billion) was calculated in the 1980s and is much more today. If offsite damages are proportional to erosion rates, an estimated $2.6 billion annual savings has resulted due to the erosion reduction achieved by farmers largely through conservation tillage.
If adjusted for inflation, this would represent a $3.5 billion in annual savings in 2002 and again would be more today. More will be forthcoming in future columns.
For more information, contact the Natural Resources Conservation Service in Kingsville or call at 592-0309 Ext. 3.