A Hedge with an Edge for Erosion Control
By Ann Perry
August 21, 2009
One way farmers can preserve soil and
protect water quality is by planting grass hedges to trap sediment that would
otherwise be washed away by field runoff. Agricultural Research Service (ARS)
scientists at the agencys
Sedimentation Laboratory in Oxford, Miss., have calculated how much soil
erosion these hedges prevent and verified predictions of the
Universal Soil Loss Equation version 2 (RUSLE2).
Wilson and agricultural engineer
Cullum collaborated with retired agricultural engineer Keith McGregor in a
series of studies over 13 years to assess the effectiveness of grass hedges for
erosion control in wide or ultra-narrow-row conventional tillage or no-till
The researchers established single-row continuous swaths of miscanthus, a
tall perennial grass, across the lower ends of 72-foot-long plots with a 5
percent slope. Then they tracked how much sediment was trapped by the
vegetation from both the wide and ultra-narrow-row conventional tillage and
no-till fields. The hedges eventually became a yard wide and were clipped two
to three times every year after the grass was 5 to 6.5 feet tall.
The scientists found that the ability of the hedges to trap sediment
increased as the hedges matured. The hedges were more effective at intercepting
sediments that washed out of conventionally tilled fields, possibly because the
eroded materials from no-till fields were composed of smaller particles.
The hedges captured approximately 90 percent of eroded sediment from
ultra-narrow-row conventionally tilled fields, and only about 50 percent of
sediment from no-till fields. Nevertheless, the actual soil loss from the
no-till plotseither with or without grass hedgeswas much less than
the conventionally tilled plots with or without grass hedges, because no-till
production helps mitigate erosion.
The team also found that hedge effectiveness was enhanced when clippings
were allowed to accumulate uphill of the hedges. But even if all the clippings
from grass hedges over 1.5 feet tall are removed for livestock feed or
bioenergy production, the hedges can still help protect against field erosion.
Hedges could be especially valuable if highly erodible lands in the
U.S. Department of Agriculture (USDA)
Program are brought back into production.
Results from this study were published in the Soil Science Society of America
ARS is the principal intramural scientific research agency of USDA.