Healthy soil and sustainable growing

["TradingPostPaul" <tradingpost@riseup.net>]

Less is more: No-till agriculture helps mitigate global warming
U.S. Department of Energy
http://www.eurekalert.org/features/doe/2005-09/dnnl-lim091605.php

Using research, technology and tractors, farmers around the world are
plotting and carrying out a small revolution-a revolution that has the
potential to transform agriculture and use it as a tool to mitigate global
warming.

The concentration of greenhouse gases—mainly carbon dioxide, CO2—is
increasing in the atmosphere at unprecedented levels. No-till agriculture
offers one way of slowing further increases in atmospheric CO2.

No-till agriculture produces crop yields similar to or better than those
obtained with conventional tillage practices, protects soil against
erosion, and results in increased storage of carbon in the soil.
Researchers at Pacific Northwest National Laboratory are contributing to
the no-till revolution by increasing understanding of the soil carbon
sequestration process.

The buildup of CO2 in the atmosphere is a result of burning fossil fuels
for energy production as well as the historical and current conversions of
forests and grasslands to agricultural use.

Plants remove CO2 from the atmosphere through photosynthesis and release
part of it back via respiration. This carbon cycling results in a net
accumulation of plant biomass. When crops are harvested, the organic carbon
in the plant residue and roots is decomposed by soil microbes, resulting in
the release of CO2 back to the atmosphere. Not all the carbon is released,
however. In aggrading natural ecosystems and well-managed agroecosystems, a
portion of the added carbon is slowly converted into soil organic matter.
Conversely, intensive tillage, erosion, inadequate nutrient management and
the conversion of forests and grasslands to agriculture have led to carbon
losses of up to 50 percent from that present in native ecosystems.

Carbon accumulation in agricultural soils can be greatly improved by
various forms of conservation practices such as no-till agriculture,
optimal nutrient management, crop rotations and converting marginal
agricultural land back to native vegetation. Carbon sequestration occurs
mainly when more carbon is added to the soil or when there is a decrease in
soil disturbance.

"The central idea behind soil carbon sequestration is that most of the soil
carbon lost worldwide due to past agricultural practices can be recovered
during the next 30 to 40 years with the application of advanced
agricultural technologies," said Cesar Izaurralde, senior scientist at
PNNL's Joint Global Change Research Institute. "There is increasing
experimental evidence to support this assertion. The challenge resides in
providing incentives on a global scale for farmers to adopt no-till and
other technologies. It also is necessary to develop monitoring systems to
demonstrate that the accumulation of soil carbon occurs because of the
adoption of these practices."

Researchers estimate that the extensive adoption of no-till agriculture,
diversified rotations, cover crops, fertility management, erosion control
and irrigation management can lead to the recovery of two thirds of the
carbon that has been lost from the soil due to conversion of native
ecosystems to agriculture and the use of conventional management practices.
That amounts to 40 to 50 billion tons of carbon. As a reference, fossil
fuel emissions of carbon to the atmosphere exceed six billion tons a year.

Izaurralde and colleagues at JGCRI and at PNNL's Richland, Wash., campus
have developed models to better understand how carbon is sequestered in the
soil. One program, supported by the U.S. Department of Energy, is Carbon
Sequestration in Terrestrial Ecosystems, CSiTE; the other, supported by the
U.S. Department of Agriculture, is the Consortium for Agricultural Soils
Mitigation of Greenhouse Gases, CASMGS.