|December 8, 2005:
When it comes to greenhouse gases, reduced tillage has
been heralded as the messiah for its ability to increase
soil carbon by capturing carbon dioxide from the air.
New work by USDA Agricultural Research Service personnel
in Minnesota may lead us to re-think this assumption.
For sometime now researchers in Michigan (Robertson
et al., 2000) have been suggesting that nitrous oxide—with
nearly 300 times the greenhouse potency of carbon dioxide--needs
to be factored into greenhouse gas calculations. Nitrous
oxides are associated with fertilizer nitrogen use and,
like soil carbon levels, can be influenced by tillage
regimes. Now, USDA-ARS soil scientist Rod Venterea and
colleagues have shown that over a two-year period, the
combination of anhydrous ammonia fertilizer use and
no-till can lead to alarmingly high nitrous oxide emissions.
The Minnesota study found that fields treated with
anhydrous ammonia had two to four times the nitrous
oxide losses compared to urea ammonium nitrate or pelleted
urea. If the ammonia was injected more than four inches
below the soil surface, however, nitrous oxide emissions
were lower in no-till fields than in conventional- or
A distinctly unfriendly side of conventional no-till
agriculture is its dependence on high rates of ammoniated
fertilizer and herbicides. Dr. David Pimentel of Cornell
University has estimated that 75 percent of conventional
no-till's fossil fuel dependence for corn production
is related to use of ammoniated fertilizer. In addition
to high energy costs, the use of synthetic nitrogen
can contribute to environmental and health problems.
In Iowa, Dr. Weyer and co-workers (2001) have associated
increased water nitrates with hyperthyroidism, increase
of insulin-dependent diabetes and bladder cancer.
According to Townsend et al. (2003), human activity
is responsible for most of the reactive nitrogen in
the biosphere, surpassing all natural processes combined.
A significant portion is related to the production of
fertilizers. This review links the global changes in
the nitrogen cycle with excessive air and water nitrogen
levels, leading to increased respiratory disease, cardiac
abnormalities and cancer.
The Rodale Institute's Farming System Trial® shows
that the high yields associated with the use of anhydrous
ammonia can be readily achieved through the use of legume
cover crops. In a legume-based organic cropping system,
high corn yields can be maintained without the high
energetic, environmental and health costs associated
with ammoniated fertilizer use (Pimentel et al., 2005).
We need to provide interested people with details of
this more regenerative system of farm production. We
need to come to the aid of farmers and consumers alike
to help improve our land, the food it produces and our
In this regard, The Rodale Institute's work on a biologically
based no-till system using mechanically killed cover
crops offers a real alternative to conventional no-till
systems based on intensive use of fertilizers and herbicides.
This is why we are so enthusiastic about our No-Till+
project, which offers real hope of regenerative agriculture
with its multiple benefits.