Carbon Footprints of Selected Field Crops Grown in Diversified Cropping Sequences On the Northern Great Plains.

Carbon footprint is defined as the amount of greenhouse gas emissions associated with a product or a service, expressed in carbon dioxide equivalence (CO2e). There is an increasing demand for carbon footprint labeling of farm products. This paper compared carbon footprints of seven field crops grown on the northern Great Plains and determined the effect of crop sequences on the carbon footprint of a durum wheat. The values of carbon footprints were estimated based on emissions from the decomposition of crop straw, roots and seeds; the manufacture of N and P fertilizers and their application rates; the production of herbicides and fungicides; and miscellaneous farm field operations. Production and application of N fertilizers accounted for about 57 to 65% of the total footprints, those from crop residue decomposition 16 to 30%, and the rest of the footprints were associated with P fertilizers, pesticides, and field operations. One kg of crop product requires 0.7 kg CO2e for canola, 0.4~0.6 kg CO2e for mustard, flaxseed and spring wheat, and 0.17~0.26 kg CO2e for chickpea, lentil, and dry pea. Durum crop preceded by a pulse crop produced grains with a carbon footprint of 673 kg CO2e, 20% lower than when the crop was preceded by a cereal crop. Similarly, carbon footprint of durum preceded by an oilseed was 744 kg CO2e, 11% lower than when after a cereal. Carbon footprint intensity was 0.25 and 0.28 kg CO2e per kg of the grain of durum grown, respectively, after a pulse and oilseed crop, which was signif6icantly lower than 0.37 for the crop grown after a cereal. Crop choices and crop sequences significantly affected carbon footprint of field crops in the northern Great Plains.