Columbus, Ohio
April 16, 2004
Increase no-till farming practices
across the planet or face serious climate, soil quality and food
production problems in the next 20 to 50 years. That warning
from scientists appeared in the journal
Science
this week.
No-till farming helps soil retain
carbon. Healthy topsoil contains carbon-enriched humus –
decaying organic matter that provides nutrients to plants. Soils
low in humus can't maintain the carbon-dependent nutrients
essential to healthy crop production, resulting in the need to
use more fertilizers.
A lack of carbon in soil may
promote erosion, as topsoil and fertilizers are often washed or
blown away from farm fields and into waterways, said
Rattan Lal, the
paper's lead author and the director of the
carbon management and
sequestration center at Ohio State University.
In no-till agriculture, farmers
plant seeds without using a plow to turn the soil. Soil loses
most of it carbon content during plowing, which releases carbon
dioxide gas into the atmosphere. Increased levels of CO2 in the
atmosphere have been associated with global climate change.
Traditional plowing, or tilling, turns over the top layer of
soil. Farmers use it for, among other reasons, to get rid of
weeds, make it easier to use fertilizers and pesticides and to
plant crops. Tilling also enriches the soil as it hastens the
decomposition of crop residue, weeds and other organic matter.
Still,
the benefits of switching to no-till farming practices outweigh
those of traditional planting.
Since
the mechanization of agriculture began a few hundred years ago,
scientists estimate that some 78 billion metric tons – more than
171 trillion pounds – of carbon once trapped in the soil have
been lost to the atmosphere in the form of CO2.
Lal and
his colleagues estimate that no-till farming is practiced on
only 5 percent of all the world's cultivated cropland. Farmers
in the United States use no-till methods on 37 percent of the
nation's cropland, which results in saving an estimated 60
million metric tons of soil CO2 annually.
"If
every farmer who grows crops in the United States would use
no-till and adopt management practices such as crop rotation and
planting cover crops, we could sequester about 300 million tons
of soil carbon each year," said Lal, who is also a professor of
soil science at Ohio State.
"Each
year, 6 billion tons of carbon is released into the planet's
atmosphere as fossil fuels are burned, and plants can absorb 20
times that amount in that period of time," he said. "The problem
is that as organisms decompose and plants breathe, CO2 returns
to the atmosphere. None of it accumulates in the soil."
Lal
admits that full-scale no-till farming practices are a
short-term fix, but it's one that will give researchers enough
time to find alternatives to fossil fuels.
"There
needs to be a global effort to adopt no-till farming practices
soon. Governments need to mandate these practices or to provide
financial incentives to farmers to adopt them," said Lal, adding
no-till methods may reduce a farmer's annual crop yield by 5 to
10 percent, at least for the first few years.
It's
also tough to ask farmers who lack the necessary financial
resources to switch to no-till methods, especially in African
and Asian countries where no-till levels are the lowest, Lal
said.
"No-till
isn't readily practiced in most of these areas due to the lack
of available financial resources and government support," he
said. "Farmers often lack the seeding equipment necessary to
drill through crop residue. And many farmers use leftover
residue from the previous year's crops for fuel or animal
fodder. So the cultivated soil gets compacted or eroded by water
and wind."
Topsoil
is also a lucrative commodity – an acre of it can bring in
$1,300 for a farmer in India, where the first few feet of soil
are often removed for brick making.
"No-till
farming isn't a substitute for finding alternatives to fossil
fuels," Lal said.
"No-till
is definitely a short-term fix, but it may buy us up to 50 years
to find alternatives to fossil fuels. If we don't heed this
warning, our planet may change drastically. There's no other
choice."
Lal
co-authored the paper with Michael Griffin, Jay Apt, Lester Lave
and M. Granger Morgan, all with
Carnegie Mellon University. |