Pulses are a low carbon footprint food
- Many studies have shown that greenhouse gas emissions can be reduced by incorporating pulses into cropping systems1, 2, 3, 4.
- In a review of carbon footprints from Canadian prairie crop production, pulse crops (peas, lentils and chickpeas) produced 65% less emissions than canola and spring wheat and had the lowest carbon footprints.
- A review paper by Lemke et al. (2007)1 shows that inclusion of one pulse crop (peas) in a four year rotation with wheat and flax can reduce greenhouse gas emissions by 13%.
- Cereals grown in diversified cropping systems including pulses also can have a lower carbon footprint, as the same amount of yield can be achieved with less inputs like nitrogen fertilizer. In one example, durum grown after a pulse crop has a 17% lower carbon footprint than durum grown after a cereal4.
- A life cycle analysis by the Saskatchewan Research Council (2011) shows that including one year of pea or lentil in a four-year crop rotation, reduces the non-renewable energy use of the entire rotation by 25 and 21%, respectively. This is again due to the reduced energy requirement of the nitrogen-fixing pulses, and the reduced fertilizer requirement of the wheat grown after the pulse crop5.
- A replication of Keystone Field to Market sustainability indicators in Western Canada shows 25% improvement in the greenhouse gas index for peas from 1981 to 2006 and a 32% improvement for lentils from 1981 to 20066.
||Lemke, R.L., Zhong, Z., Campbell, C.A. and Zentner, R. 2007. Can Pulse Crops Play a Role in Mitigating Greenhouse Gases from North American Agriculture? Agronomy Journal. 99: 1719–1725.
||Dusenbury, M.P., Engel, R.E., Miller, P.R., Lemke, R.L. and Wallander, R. 2008. Nitrous Oxide Emissions from a Northern Great Plains Soil as Influenced by Nitrogen Management and Cropping Systems. Journal of Environmental Quality. 37: 542-550.
||Gan, Y., Liang, C., Hamel, C., Cutforth, H. and Wang, H. 2011. Strategies for reducing the carbon footprint of field crops for semiarid areas. A review. Agronomy for Sustainable Development.
||Gan, Y., Liang, C., Wang, X. and McConkey, B. 2011. Lowering carbon footprint of durum wheat by diversifying cropping systems. Field Crops Research. 122: 199–206.
||Life Cycle and Socio-Economic Analysis of Pulse Crop Production and Pulse Grain Use in Western Canada. Saskatchewan Research Council Publication No. 12135-1E11, March 2011. (not published as of February 2012)
||Application of Sustainable Agriculture Metrics to Selected Western Canadian Field Crops. 2011. Serecon Management Consulting.
Can Pulse Crops Play a Role in Mitigating Greenhouse Gases from North American Agriculture?
This article summarized many different experiments investigating the impact of pulse crops on greenhouse gas emissions. It was published in the peer-reviewed Agronomy Journal in 2007. Pulse crops affect the amount of carbon dioxide, nitrous oxide, and methane emitted from the soil they are grown in.
Research shows that crop rotations containing a pulse crop have lower overall greenhouse gas emissions than those that do not include a pulse crop. This is because up to 70% of the non-renewable energy used in Western Canadian cropping systems is due to the use of fertilizers, particularly nitrogen. Pulses supply their own nitrogen, reducing the need for added nitrogen fertilizer. Research on nitrous oxide emissions specifically is limited, but shows that emissions tend to be lower for pulse crops compared to fertilized cereal crops. The more often a pulse crop is grown, the more greenhouse gas emissions are reduced. For example, a 17-year study at Swift Current, SK showed that greenhouse gas emissions were decreased by 31% annually when lentils were included in rotation with spring wheat. A similar study at Indian Head, SK showed an 18% reduction in yearly greenhouse gas emissions when peas were included in rotation with spring wheat, winter wheat, and flax.
Nitrous Oxide Emissions from a Northern Great Plains Soil as Influenced by Nitrogen Management and Cropping Systems
In this peer-reviewed article published in the Journal of Environmental Quality in 2008, the authors measured the amount of nitrous oxide gas emitted from agricultural soils in Montana. The objective of the study was to determine how crop rotation and nitrogen fertilizer use affect nitrous oxide emissions.
Three different crop rotations were studied over two years. Crop rotations included a wheat-pea rotation and a wheat-wheat rotation, both grown under zero tillage conditions. The crops were grown with three different amounts of nitrogen fertilizer.
Nitrous oxide emissions were minimal while the pea crop was growing. The study also looked at nitrous oxide intensity, which is the amount of nitrous oxide emitted for each kilogram of harvested crop. The nitrous oxide intensity was lower for the wheat-pea rotation than for the wheat-wheat rotation. In other words, the wheat-pea rotation had less nitrous oxide emitted per kilogram of crop harvested. Traditionally, cropping systems in Montana include a fallow year where no crop is produced. This research shows that by replacing the fallow year with a pulse crop, more grain can be produced without a significant increase in nitrous oxide emissions.
Strategies for reducing the carbon footprint of field crops for semiarid areas. A review.
This peer-reviewed article was published in the journal Agronomy and Sustainable Development in 2010. The study compared the carbon footprint of canola, mustard, flax, spring wheat, chickpea, pea, and lentil. In addition, the effect of crop rotation on the carbon footprint of a durum wheat crop was determined.
The carbon footprint was measured as the amount of carbon dioxide emitted per kilogram of grain produced. For each crop, carbon footprints were calculated by adding the greenhouse gas emissions from the decomposition of crop residue, the manufacture and use of fertilizers and pesticides, and other miscellaneous farm operations. The amount of nitrogen contributed by various pulse crops was also estimated.
The production and application of nitrogen fertilizer accounted for up to two-thirds (57% to 65%) of the carbon footprint of each crop. The three pulse crops studied (chickpea, pea, and lentil) had the lowest carbon footprints – an average of two-thirds lower than canola or spring wheat. When durum wheat was grown after a pulse crop, it had a carbon footprint that was 46% lower than if it was grown after spring wheat. Worldwide, it was calculated that pulses produce about 21 million tonnes of nitrogen per year. The article concludes that better farming practices (including the use of pulse crops) can lower the average carbon footprint by 24 to 37%.
Lowering carbon footprint of durum wheat by diversifying cropping systems.
This 2011 article in the peer-reviewed Field Crops Research Journal studied the carbon footprint of durum wheat. Durum wheat was grown under zero tillage conditions in nine different crop rotations. Each three-year rotation included two years of pulses, oilseeds, or spring wheat. This was followed by durum wheat in the third year. The pulses studied were lentils, chickpeas, and peas.
The carbon footprint of each rotation was calculated by adding the greenhouse gases from: 1) farming operations including seeding, spraying, and harvesting; 2) the production, transportation, storage, delivery, and application of fertilizers and pesticides; and 3) the decomposition of crop residues.
The study concluded that including pulses in crop rotations can substantially lower the carbon footprint of a subsequent durum wheat crop by up to one-third. When durum was grown after a pulse crop, the carbon footprint was 28% less than when grown after spring wheat. When durum was grown after two consecutive years of pulse crops, the carbon footprint was 34% lower than when durum was grown after two years of cereal crops. The lower carbon footprint was primarily due to the reduction in nitrogen fertilizer requirement when durum was grown after a pulse crop. Pulses can also lower the carbon footprint by diversifying the crop rotation, leading to fewer weed and pest problems.
Life Cycle and Socio-Economic Analysis of Pulse Crop Production and Pulse Grain Use in Western Canada
Not published as of February 2012. Link and summary to be added once available
Application of Sustainable Agriculture Metrics to Selected Western Canadian Field Crops