Dirt: The Erosion of Civilizations - Kootenay Local Agricultural Society

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No-till farming is very effective at reducing soil erosion; leaving the
ground covered with organic debris can bring soil erosion rates down close
to soil production rates—with little to no loss in crop yields. In the late
1970s, one of the first tests of the effect of no-till methods in Indiana
reported a more than 75 percent reduction in soil erosion from cornfields.
More recently, researchers at the University of Tennessee found that no-till
farming reduced soil erosion by more than 90 percent over conventional
tobacco cultivation. Comparison of soil loss from cotton fields in northern
Alabama found that no-till plots averaged two to nine times less soil loss
than conventional-till plots. One study in Kentucky reported that no-till
methods decreased soil erosion by an astounding 98 percent. While the
effect on erosion rates depends on a number of local factors, such as the
type of soil and the crop, in general a 10 percent increase in ground surface
cover reduces erosion by 20 percent, such that leaving 30 percent of the
ground covered reduces erosion by more than 50 percent.
Lower erosion rates alone do not explain the rapid rise in no-till agriculture’s
popularity. No-till methods have been adopted primarily because
of economic benefits to farmers. The Food Security Acts of 1985 and 1990
required farmers to adopt soil conservation plans based on conservation
tillage for highly erodible land as a condition for participating in popular
USDA programs (like farm subsidies). But conservation tillage has proven
to be so cost-effective that it also is being widely adopted on less erodible
fields. Not plowing can cut fuel use by half, enough to more than offset
income lost to reduced crop yields, translating into higher profits. It also
increases soil quality, organic matter, and biota; even earthworm populations
are higher under no-till methods. Although adopting no-till practices
can initially result in increased herbicide and pesticide use, the need
declines as soil biota rebound. Growing experience in combining no-till
methods with the use of cover crops, green manures, and biological pest
management suggests that these so-called alternative methods offer practical
complements to no-till methods. Farmers are adopting no-till methods
because they can both save money and invest in their future, as increasing
soil organic matter means more fertile fields—and eventually lower outlays
for fertilizer. The lower cost of low-till methods is fueling growing interest
even among large farming operations.
No-till agriculture has another advantage; it could provide one of the
few relatively rapid responses to help hold off global warming. When soil
is plowed and exposed to the air, oxidation of organic matter releases carbon
dioxide gas. No-till agriculture has the potential to increase the
dirty business