Carbon footprint of spring barley in relation to preceding oilseeds and N fertilization
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Carbon footprint of field crops can be lowered through improved cropping practices. The objective of this study was to determine the carbon footprint of spring barley (Hordeum vulgare L.) in relation to various preceding oilseed crops that were fertilized at various rates of inorganic N the previous years. System boundary was from cradle-to-farm gate.
Materials and methods
Canola-quality mustard (Brassica juncea L.), canola (Brassica napus L.), sunflower (Helianthus annuus L.), and flax (Linum usitatissimum L.) were grown under the N fertilizer rates of 10, 30, 70, 90, 110, 150, and 200 kg N ha−1 the previous year, and spring barley was grown on the field of standing oilseed stubble the following year. The study was conducted at six environmental sites; they were at Indian Head in 2005, 2006 and 2007, and at Swift Current in 2004, 2005 and 2006, Saskatchewan, Canada.
Results and discussion
On average, barley grown at humid Indian Head emitted greenhouse gases (GHGs) of 1,003 kg CO2eq ha−1, or 53% greater than that at the drier Swift Current site. Production and delivery of fertilizer N to farm gate accounted for 26% of the total GHG emissions, followed by direct and indirect emissions of 28% due to the application of N fertilizers to barley crop. Emissions due to N fertilization were 26.6 times the emission from the use of phosphorous, 5.2 times the emission from pesticides, and 4.2 times the emission from various farming operations. Decomposition of crop residues contributed emissions of 173 kg CO2eq ha−1, or 19% of the total emission. Indian Head-produced barley had significantly greater grain yield, resulting in about 11% lower carbon footprint than Swift Current-produced barley (0.28 vs. 0.32 kg CO2eq kg−1 of grain). Emissions in the barley production was a linear function of the rate of fertilizer N applied to the previous oilseed crops due to increased emissions from crop residue decomposition coupled with higher residual soil mineral N.
The key to lower the carbon footprint of barley is to increase grain yield, make a wise choice of crop types, reduce N inputs to crops grown in the previous and current growing seasons, and improved N use efficiency.
KeywordsCarbon footprint Life cycle assessment N use efficiency No-till practices
We gratefully acknowledge the excellent technical assistance provided by Cal McDonald, Lee Poppy, and Ray Leshures at Swift Current and Roger Geremia, Orla Willoughby, and Randy Shiplackand at Indian Head for conducting the field experiments, and the funding provided by Saskatchewan Canola Development Commission and the Matching Investment Initiative of Agriculture and Agri-Food Canada. We also thank Mr. Dirk Anderson for providing annual estimates of the growing season potential evapotranspiration rates for the experimental sites.
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