Nitrous Oxide (N2O) Emisisons On Conversion of Conservation Reserve Program (CRP) Land to Biofuel Crops Under till and No-till Practices.

Returning land enrolled in the Conservation Reserve Program (CRP) to crop land can be an option to meet the demand for expanding biofuel production. However, failing to consider GHG emissions caused by crop activities such as tillage and fertilization will overestimate the ability of biofuels to reduce GHG emissions. We studied the impacts of tillage and fertilization on N₂O emissions during the first two years of CRP conversion to either corn, switchgrass, or restored prairie. Soybean was planted as the conversion year crop on all three sites in southwestern Michigan in 2009. For 2009 total emissions of N₂O were three times higher under conventional tillage (CT) than under no-till (NT) (6.69 vs. 2.72 kg N₂O-N ha^-1; p<0.01). In 2010 N₂O fluxes were also higher under CT across all three plants corn, switchgrass, and prairie (3.77 vs. 1.45 kg N₂O-N ha^-1; p<0.01). Among corn, switchgrass, and prairie plantings, averaged cumulative soil N₂O emissions from corn (4.58 kg N₂O-N ha^-1), which was fertilized, were three times larger than emissions from the two unfertilized cellulosic crops (1.63 kg N₂O-N ha^-1; p<0.05); there were no significant differences between the switchgrass and prairie plots. Using no-till practices during the conversion year can substantially reduce the N₂O cost of CRP conversion to biofuel crops, as can converting to perennial cellulosic crops rather than corn.