Dr. Paul's Research Perspectives
New reasons to perfect organic no-till
USDA study finds conventional no-till is no panacea when it comes to greenhouse gas emissions.

By Paul Hepperly

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 conservation-till fields.

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 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 benefits.