Page 245 - Environment: The Science Behind the Stories

at Kansas State University. Nate became one of 27 farmers Contour farming Water running down a hillside with lit-
working with extension agents from Iowa State University to tle plant cover can carry soil away, so farmers have developed
use his own land to experimentally test the effectiveness of no- methods for cultivating slopes. Contour farming (Figure 9.15b)
till farming versus several types of tilling. After three years, consists of plowing furrows sideways across a hillside, per-
his no-till fields produced as much corn as his conventional pendicular to its slope and following the natural contours of
fields while requiring less time and money. Ronsiek says he the land. In contour farming, the side of each furrow acts as a
can clearly see how water infiltrates better in the no-till fields small dam that slows runoff and captures soil. Contour farm-
and how those fields suffer less erosion. “If there is a way to ing is most effective on gradually sloping land with crops that
do it, [the extension agents] know it,” he says. “NRCS keeps grow well in rows.
me up-to-date with the latest in conservation techniques, prac-
tices, and ways to save money.”
Terracing On very steep terrain, terracing (Figure 9.15c)
is the most effective method for reducing erosion. Terraces
are level platforms, sometimes with raised edges, that are cut
Soil conservation is thriving worldwide into steep hillsides to contain water from irrigation or precipi-
The SCS and NRCS have served as models for efforts else- tation. Terracing transforms slopes into series of steps like a
where in the world. In South America, no-till agriculture has staircase, enabling farmers to cultivate hilly land without los-
exploded in popularity and now covers a majority of farm- ing huge amounts of soil to water erosion. Farmers have used
land in Argentina, Brazil, and Paraguay. The shift to no-till terracing for centuries in mountainous regions, such as the
farming across this vast region came about largely through foothills of the Himalayas and the Andes. Terracing is labor-
local grassroots organization by farmers, with the help of intensive to establish but in the long term is likely the only
agronomists and government extension agents who provided sustainable way to farm in mountainous terrain.
them information and resources. Southernmost Brazil alone
boasts thousands of “Friends of the Land” clubs in which Intercropping Farmers also minimize erosion by inter-
local farmers collaborate with trained experts. cropping, planting different crops in alternating bands or other
From Argentina to Iowa, no-till agriculture is one of many spatially mixed arrangements (Figure 9.15d). Intercropping
approaches to soil conservation. Hugh Hammond Bennett helps slow erosion by providing more ground cover than does
advocated a complex approach, combining techniques such a single crop. Like crop rotation, intercropping reduces vul-
as crop rotation, contour farming, strip cropping, terracing, nerability to insects and disease and, when a nitrogen-fixing
grazing management, and reforestation, as well as wildlife legume is used, replenishes the soil. In southern Brazil, some
management. Such measures are now widely applied in many no-till farmers intercrop cover crops with food crops such as
places around the world. maize, soybeans, wheat, onions, cassava, grapes, tomatoes,
tobacco, and orchard fruit.

Farmers protect soil in many ways Shelterbelts A widespread technique to reduce erosion
from wind is to establish shelterbelts, or windbreaks (Figure
A number of farming techniques can reduce the impacts of 9.15e). These are rows of trees or tall shrubs that are planted
conventional cultivation on soils (Figure 9.15). Some of these along the edges of fields to slow the wind. On North Amer-
have been promoted by the SCS since the Dust Bowl. Oth- ica’s Great Plains, fast-growing species such as poplars are
ers, like no-till farming in Iowa, have found popularity more often used. Shelterbelts can be combined with intercropping
recently. Still others have been practiced by some cultures for by planting mixed crops in rows surrounded by or interspersed
centuries. with rows of trees that provide fruit, wood, or protection from
wind.
Crop rotation In crop rotation, farmers alternate the type
of crop grown in a given field from one season or year to the
next (Figure 9.15a). Rotating crops returns nutrients to the soil, Conservation tillage Conservation tillage describes an
minimizes erosion from letting fields lie fallow, and can break array of approaches that reduce the amount of tilling rela-
cycles of disease associated with continuous cropping. Many tive to conventional farming; one common definition is any
U.S. farmers rotate their fields between wheat or corn and method of limited tilling that leaves more than 30% of crop
soybeans from one year to the next. Soybeans are legumes, residue covering the soil after harvest. No-till farming is the
plants with specialized bacteria on their roots that fix nitrogen ultimate form of conservation tillage.
(p. 144), revitalizing soil with nutrients. Crop rotation also
reduces insect pests; if an insect is adapted to feed and lay No-till farming has many benefits
eggs on one crop, planting a different type of crop will leave
its offspring with nothing to eat. In a practice similar to crop To plant using the no-till method (Figure 9.15f), a tractor pulls
rotation, many no-till farmers, like the Nielsens in Iowa, plant a “no-till drill” (Figure 9.16) that cuts furrows through the O
cover crops such as clover (a nitrogen-replenishing legume) horizon of dead weeds and crop residue and the upper levels
to prevent erosion during times of year when the main crops of the A horizon. The device drops seeds into the furrow and
are not growing. closes the furrow over the seeds, minimizing disturbance to
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