Using No till Practices to Reduce Nitrous Oxide (N2O) Emissions During Conversion of Conservation Reserve Program (CRP) Land to Biofuel Crops.

High commodity prices and expanding biofuel production increases demand for cropland, which is expected to induce Conservation Reserve Program (CRP) land to return to production. We studied the impacts of tillage on N2O emissions during the initial phase of CRP land conversion to either corn, switchgrass, or restored prairie. Either tilled or no-till soybean was planted into replicated plots at three sites in southwestern Michigan in 2009, and in 2010 the sites were subsequently planted to corn, switchgrass, or native prairie, respectively. Conversion substantially increased N2O fluxes, exacerbated by tillage: in 2009 total emissions of N2O were three times higher under conventional tillage (CT) than under no-till (NT) (7.03 vs. 2.37 kg N2O-N ha-1; p<0.01) and were 4.6 times higher in the no-till (NT) soybeans than in an unconverted CRP reference site (2.37 vs. 0.51 kg N2O-N ha-1; p<0.01). In 2010 N2O fluxes were also higher under CT across all three crops: corn, switchgrass, and prairie (3.77 vs. 1.45 kg N2O-N ha-1; p<0.01). In 2011, we found no significant differences in N2O emissions between the tilled and no-till plots. Additionally, there were no significant yield difference between till and no-till treatments in any of the 3 years. Using no-till practices during CRP conversion years can considerably reduce N2O emissions.