Cover crops support the climate change mitigation potential of agroecosystems

Table 2. Calculation of the net climate change mitigation impact of cover crops during an annual cropping cycle. EU-27 average per hectare (ha) EU-27 total Unit Mean Low (-95% confidence level) High (+95% confidence level) Unit Mean Low (-95% confidence level) High (+95% confidence level) Area 1,000 ha 15,092.14 14,785.60 15,398.67 Average yield Mg ha-1 7.88 7.46 8.31 Relative yield gain % 8.8% 2.9% 14.8% Absolute yield gain Mg ha-1 0.70 0.21 1.23 Carbon opportunity cost maize kg CO2e kg-1 2.10 2.10 2.10 Carbon land benefit based on maize yield gain Mg CO2e ha-1 1.46 0.45 2.59 1,000 Mg CO2e 22,086.83 6,631.87 39,805.69 Carbon sequestration Mg CO2 ha-1 1.43 0.86 2.01 1,000 Mg CO2 21,632.51 12,701.51 30,915.61 Nitrogen fixation kg N ha-1 52.49 32.06 72.92 Reduced nitrogen leaching kg N ha-1 38.82 19.13 58.51 Total nitrogen fertilizer savings kg N ha-1 91.32 51.19 131.44 Nitrogen fertilizer emissions kg CO2e kg N-1 11.23 9.02 13.43 Carbon benefit based on nitrogen fertilizer savings Mg CO2e ha-1 1.03 0.46 1.77 1,000 Mg CO2e 15,474.08 6,830.39 27,187.04 Reduced N2O emissions due to less leaching Mg CO2e ha-1 0.10 -0.15 0.35 1,000 Mg CO2e 1,495.60 -2,218.43 5,362.37 Albedo change Mg CO2e ha-1 0.20 -0.37 0.78 1,000 Mg CO2e 3,087.10 -5,514.25 12,042.49 Total climate benefit Mg CO2e ha-1 4.22 1.25 7.49 1,000 Mg CO2e 63,776.11 18,431.09 115,313.18 N2O emissions Mg CO2e ha-1 0.04 -0.02 0.09 1,000 Mg CO2e 555.77 -306.57 1,453.41 Foregone benefits due to cover crop seed land use Mg CO2e ha-1

0.28 0.27 0.29 1,000 Mg CO2e 4,180.56 3,970.76 4,395.55 Production emissions cover crop seed Mg CO2e ha-1 0.39 0.08 0.70 1,000 Mg CO2e 5,920.55 1,194.38 10,837.69 Processing, packaging, and transport of cover crop seed Mg CO2e ha-1 0.08 0.08 0.08 1,000 Mg CO2e 1,182.71 1,158.69 1,206.74 Additional machinery operations l Diesel ha-1 45.29 32.44 58.13 Diesel emissions kg CO2 l-1 3.13 3.13 3.13 Additional machinery operations Mg CO2 ha-1 0.14 0.10 0.18 1,000 Mg CO2e 2,140.93 1,502.51 2,804.02 Total climate cost Mg CO2e ha-1 0.93 0.51 1.34 1,000 Mg CO2e 13,980.53 7,519.77 20,697.40 (Continued) PLOS ONE Cover crops support the climate change mitigation potential of agroecosystems PLOS ONE | https://doi.org/10.1371/journal.pone.0302139 May 8, 2024 6 / 20