The type of fertilizer used, and the manner in which it is applied, can make or break reduced tillage’s ability to control greenhouse gases, Agricultural Research Service (ARS) scientists report.

No-till and reduced tillage are promoted as a way farmers can reduce greenhouse gas concentrations in the atmosphere by storing more carbon in soil. But there has been limited information on how tillage or other farm practices affect soil emissions of greenhouse gases other than carbon dioxide.

A study conducted by ARS soil scientist Rod Venterea on the effects of long-term tillage techniques and fertilizer practices has shown that, if not done with care, reduced tillage practices can increase emissions of more powerful greenhouse gases, particularly nitrous oxide. At 300 times the strength of carbon dioxide, nitrous oxide can easily offset the benefit of carbon dioxide reduction. Venterea works at the ARS Soil and Water Management Unit in St. Paul, Minn.

Farm fields are the biggest source of nitrous oxide emissions in the United States, with up to one-third of the agricultural emissions coming from farms in the north central region of the country.

Venterea and colleagues have shown that farmers using no-till should inject nitrogen fertilizer more than 4 inches below the soil surface, beneath the layer of soil that is most conducive to nitrous oxide production.

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