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Lal. Carbon Footprints 2026, 5, 10 Page 11 of 20

security on the other. In western Kenya, Piikki et al. suggested identification of hotspots for Achievable
[70]
Soil Carbon Sequestration and Soil Fertility Improvement, which indicates the primary benefits of soil C
sequestration for managing and enhancing soil fertility and productivity. In this context, Moinet et al. [71]
candidly remarked that it is pertinent to focus on “C for soils, not soils for C”, and suggested moving away
from global targets for SOC sequestration in agricultural soils.

NATIONAL AND GLOBAL POTENTIAL OF SOIL CARBON SEQUESTRATION
In addition to conducting plot-scale controlled studies for measuring the rate of soil C sequestration and
understanding the basic processes, practical aspects of potential of soil C sequestration at regional, national
and global scales have also been studied. Izumi and Wagai estimated that increasing drought tolerance of
[59]
the food production systems in global drylands could enhance sequestration by 4.87 Pg C and reduce decadal
mean global warming by 0.011 °C through achievement of multiple development goals by enhancing SOC
stock in C-poor or C-depleted soils especially in drier regions of the world. Paustian et al. reported that
[17]
4-5 Pg CO /year is the upper limit for global biophysical potential with complete adoption of BMPs, and the
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potential may be increased to 8 Pg CO /year on a long-term basis. Lessman et al. estimated global C
[72]
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sequestration potential of 0.44 to 0.68 Pg C/year and a more realistic rate of 0.28 to 0.43 Pg C/year compared
with an estimate of 3 Pg C/year by Bangroo et al. . The reasons for the general large range of estimates in
[73]
the literature of 0.1-2 Pg C/year must be understood. Thus, it is important to know the achievable rather
[73]
than potential level of SOC sequestration, and potential vs. actual capacity to sequester C.
The technical potential of the dryland cropping region of the Pacific Northwest part of the U.S. was assessed
by Brown and Huggins [74] , who reported that 75% of converted native land lost at least 0.14 to
0.70 MgC/ha/year over an average of 55 to 74 years. Thus, adoption of CA was predicted to increase SOC
stock by 0.12 to 0.21 MgC/ha/year (Mg = megagram = 10 gram = 1 metric ton) over 10 to 12 years. Brown
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and Huggins also reported that as compared to annual cropping, mixed perennial-annual systems would
[74]
sequester SOC at the rate of 0.65 MgC/ha/year. Follett and Reed outlined the importance of soil C
[75]
sequestration in global grazing land use of ~3.7 B ha and its policy implications. They estimated that
[75]
grazing land can remove 20% of the CO emitted from global deforestation and land use change and provide
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societal (environmental and economic) benefits including those on soil or water resources, air quality,
human and wildlife habitat and aesthetics. Economic benefits emerge from trading and exchanging goods
and services generated by grazing at local, regional and global levels. Follett and Reed argued that in-depth
[75]
discussions of U.S. policy issues are needed because of the importance of soil C sequestration in terrestrial
ecosystems. In another study, Follett estimated that tillage management and cropping systems in the U.S.
[76]
have soil C sequestration potential of 30 to 105 Tg C/year (Tg = teragram = 10 g = 1 million metric ton).
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There is a lot of variation in available rate of SOC sequestration, such as under the Conservation Reserve
Program or CRP , which needs to be understood in terms of the cause-effect relationship. Based on studies
[77]
on restoration of minelands in Ohio, USA, Shrestha and Lal reported the rate of SOC sequestration of 0.1
[78]
to 3.1 Mg/ha/year in grassland and 0.7 to 4 Mg/ha/year in forest lands. Shrestha and Lal also estimated that
[78]
restoration of mineland in the U.S. could offset 16 Tg CO /year.
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In China, Zuo et al. estimated that cropland soils (0-20 cm depth) store 4.5 to 5 Pg C, and between 1980
[79]
and 2010, total SOC stock increased from 29-35 Mg C /ha to 33-36 Mg C/ha with an annual rate of increase
of 113 kg C/ha/year. Soil C sequestration potential of Mediterranean region has also been estimated.
Vicente et al. reported that the highest soil C sequestration rate of 5.1 Mg C/ha/year was observed with
[80]
application of CA in olive orchards. In Australia, Viscarra Rossel et al. reported that the 0-30 cm soil layer
[81]
of the continent contains ~25 Pg C, and croplands provide significant potential for C sequestration.