MADISON, WI, SEPTEMBER 6, 2011 -- Measuring the emission of greenhouse gases from croplands should take into account the crops themselves.
That's the conclusion of a study in the Sept.-Oct. issue of the Journal of Environmental Quality, which examined the impact of farm practices such as tillage on the greenhouse gas, nitrous oxide. Expressing emissions per unit of crop yield rather than on a more conventional per area basis produced very different results, says the study's leader, Rod Venterea, research soil scientist with the United States Department of Agriculture's Agricultural Research Service.
In particular, his team found that total nitrous oxide emissions were not significantly affected by tillage practices when expressed on an area basis. When they were calculated per unit yield of grain, however, emissions were significantly greater under no-tillage compared with conventional tillage. A byproduct of many agricultural systems, nitrous oxide is a potent greenhouse gas (GHG) with a heat-trapping potential more than 300 times that of carbon dioxide.
The findings have important implications for how the greenhouse gases generated by agriculture are reported, evaluated, and potentially mitigated. Nitrous oxide emissions were slighter higher under no-till on a per area basis in the study, Venterea explains, but not high enough to differ statistically from those under conventional tillage. "But when we added in the fact that no-tillage also reduced yields, the effect of tillage did become significant," he says. "The point is that you need to look at both nitrous oxide emissions and yield together."
While previous studies have shown that practices like fertilizer and tillage management can affect nitrous oxide emissions, relatively few have reported the effects of these practices on crop performance at the same time. In addition, GHG emissions are commonly expressed with respect to area of field: for example, kilogram nitrou
|Contact: Sara Uttech|
American Society of Agronomy