...From the pages of Agricultural Research magazine
Drought Survival With Conservation Tillage
Sometimes the adage that less is more certainly rings
true. That's the case with conservation tillage.
Conservation tillage reduces the amount of soil disturbance
on a field because it leaves crop residue on the soil surface. With
conventional tillage, plant residue is removed or incorporated into
the soil. Conservation tillage helps to reduce runoff and soil erosion,
a particular problem with the sandy soils of the southeastern United
Southeastern soils have been intensively cropped and are
prone to drought and erosion. While rainfall registers about 50 inches
per year, growers often have to irrigate their crops during extended
drought periods. Producers in this region face a major problem: maintaining
crop yields and water-use efficiency while addressing soil and water
quality concerns associated with sediment, fertilizer, and pesticide
losses to off-site areas.
Scientists at the Southeast Watershed Research Laboratory
in Tifton, Georgia, are evaluating conservation tillage systems to measure
how well they reduce runoff and erosion, increase plant-available water
in soil, and improve overall soil productivity. Conservation tillage
systems can either be no-till, in which crops are planted through the
previous crop's residue; or strip-till, in which crops are planted in
tilled rows 4-6 inches wide.
The research, led by soil scientist Clint Truman and hydraulic
engineer David Bosch, indicates that strip-till reduces runoff and erosion,
increases water infiltrating the soil, and improves soil quality. "This
research could conceivably help producers increase water-use efficiency
and reduce irrigation. By doing so, they could increase the profit margin
while maintaining water supplies and minimizing off-site environmental
contamination," says Truman.
Plant residue left on the ground acts as a barrier to
water evaporation from the field. It also keeps raindrops from falling
directly on the soil, which decreases movement of soil, pesticides,
and nutrients off the field.
The study site was on 4.6 acres on the University of Georgia
Gibbs Farm located in Tifton and was divided into six half-acre plots,
with a seventh 1-acre plot set aside for companion rainfall-simulation
studies. A crop rotation of cotton and peanutscommon crops in
the Southeastwas used.
The study, which began in 1999, makes a good case for
conservation tillage, in this case strip-till. In the first 3 years,
surface runoff from the conventional-till plots was considerably greater
than that from the strip-till plots. Strip-till plots showed 3 to 9
percent of rainfall ran off the surface, while in the conventionally
tilled plots 12 to 22 percent of rainfall ran off. Peak surface runoff
rates observed from the conventional-till plots were up to five times
greater than those observed from strip-till plots.
In simulated-rainfall studies, runoff characteristics
for strip-till and conventional-till systems changed during the study.
In the fall of 1999, no differences were observed in the runoff volumes
from the two tillage systems. In later simulations, researchers observed
about twice the runoff from the conventional-till plots as from the
Another plus for strip-till systems: soil loss from these
plots was consistently lower than from the conventional-till plots.
In the fall of 2000, soil loss from conventional-till plots was more
than four times that from the strip-till plots, increasing to five times
by the spring of 2001. "This data shows that strip-till systems
have the potential to substantially decrease sediment loss from fields,"
Strip-till systems may be catching on. Georgia farmers'
use of strip-till systems has increased about 35 percent since 1998,
with acreage approaching 950,000 acres in 2002about 28 percent
of the total cultivated acres for that year.By Sharon
Durham, Agricultural Research Service Information Staff.
This research is part of Water Quality and Management
(#201) and Soil Resource Management (#202), two ARS National Programs
described on the World Wide Web at www.nps.ars.usda.gov.
"Drought Survival With Conservation Tillage" was published in the May 2003 issue of Agricultural Research magazine.