Sustainable Agriculture Literature Review - Boulder County

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by switching from conventional tillage continuous corn to no-till corn–bean farmers would
increase annual average net returns by $228 per hectare while reducing annual net
GWP by 929 kg CO2 equivalents per hectare. 118
Adopting reduced or limited tillage practices may also affect N2O emissions but the net
effects are not well-quantified across different agricultural systems, climatic conditions,
and soil types. 119, 120, 121 Reviewed literature relevant to the agricultural ecosystem in
Boulder County showed that overall there is a net decrease in N2O emissions associated
with minimal tillage practices. 122, 123, 124 While this seems to be the case in Boulder
County, it is important to note that in other areas nationally, reduced tillage may increase
N2O emissions, while elsewhere it may have no measurable influence. 125
While the majority of the scientific community sees the potential of no-till agriculture and
organic farming methods to sequester more carbon, there have been some objections
raised about the longevity of the benefits. Of particular concern is the depth at which the
carbon is preserved, as the majority of studies have only measured soil organic carbon
in the top 20 centimeters (cm) of the soil profile. A study reviewing 11 different soils
across the United States found carbon sequestration in the top 20 cm, but did not find
significant carbon reserves below that 20 cm profile. 126 This means that if that soil were
to be tilled again, most of the sequestered carbon would be released, negating potential
benefits. More research is being conducted on soil carbon sequestration to determine at
what depth carbon is stored. It is likely that carbon, like topsoil, can be accumulated at
greater and greater depths as more material is applied, however, this is an area for
further research.
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