Dirt: The Erosion of Civilizations - Kootenay Local Agricultural Society

mulching, which can triple the mass of soil biota, and application of manure,
which can increase the abundance of earthworms and soil microorganisms
fivefold. Depending on the particular crop and circumstances, a
dollar invested in soil conservation can produce as much as three dollars’
worth of increased crop yields. In addition, every dollar invested in soil and
water conservation can save five to ten times that amount in costs associated
with dredging rivers, building levees, and flood control in downstream
areas. Although it is hard to rally and sustain political support for treating
dirt like gold, American farmers are rapidly becoming world leaders in soil
conservation. Because it is prohibitively expensive to put soil back on the
fields once it leaves, the best, and most cost-effective strategy lies in keeping
soil on the fields in the first place.
For centuries the plow defined the universal symbol of agriculture. But
farmers are increasingly abandoning the plow in favor of long-shunned notill
methods and less aggressive conservation tillage—a catchall term for
practices that leave at least 30 percent of the soil surface covered with crop
residue. Changes in farming practices over the past several decades are revolutionizing
modern agriculture, much as mechanization did a century
ago—only this time, the new way of doing things conserves soil.
The idea of no-till farming is to capture the benefits of plowing without
leaving soils bare and vulnerable to erosion. Instead of using a plow to turn
the soil and open the ground, today’s no-till farmers use disks to mix
organic debris into the soil surface and chisel plows to push seeds into the
ground through the organic matter leftover from prior crops, minimizing
direct disturbance of the soil. Crop residue left at the ground surface acts
as mulch, helping to retain moisture and retard erosion, mimicking the
natural conditions under which productive soils formed in the first place.
In the 1960s almost all U.S. cropland was plowed, but over the past
thirty years adoption of no-till methods has grown rapidly among North
American farmers. Conservation tillage and no-till techniques were used
on 33 percent of Canadian farms in 1991, and on 60 percent of Canadian
croplands by 2001. Over the same period conservation tillage grew from
about 25 percent to more than 33 percent of U.S. cropland, with 18 percent
managed with no-till methods. By 2004, conservation tillage was practiced
on about 41 percent of U.S. farmland, and no-till methods were used on
23 percent. If this rate continues, no-till methods would be adopted on the
majority of American farms in little more than a decade. Still, only about
5 percent of the world’s farmland is worked with no-till methods. What
happens on the rest may well shape the course of civilization.
dirty business 211