|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
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 own health.
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