Climate Change Mitigation - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 124

it is recognized that the scarcity of available
information does not allow for precise agro-
nomic recommendation, and even more at-
tention needs to be paid to the availability
of the raw material and the time and energy
necessary for preparing the material.
Moreover, the benefit of CRW as com-
pared with non-woody amendments is poor-
ly documented, and thus the comparative
advantage in relation to more traditional in-
puts is not proved.
Recently, the World Bank (2012) pub-
lished a report containing a meta-analysis
that included more conventional agricul-
tural practices aimed at GHG mitigation, as
well as other technical solutions (e.g. bio-
chars), and using more resolved land man-
agement categories and focusing in Latin
America, Africa and Asia ( Fig. 9.2 ).
Other options that have been evaluated
recently for GHG mitigation potential in-
clude organic farming practices. Gattinger
et al . (2012) performed a quantitative as-
sessment based on pairwise comparisons
of organic versus non-organic farming systems
from 74 published studies. The authors found
significant higher values for organic sys-
tems of 0.350 ± 0.108 kg C m − 2 for stocks
and 0.045 ± 0.021 kg C m − 2 year − 1 for se-
questration rates. But they failed to iden-
tify clear drivers and when they used a
more restrictive approach, excluding data
sets with lowest data quality (e.g. excluding
studies lacking direct measurements of soil
bulk density), the sequestration rates were
non-significant. Moreover, Leifeld et al .
(2013) argued that the study by Gattinger
et al . (2012) was biased and that their con-
clusion that practices central to organic
farming could mitigate climate change
through C sequestration in soils was mis-
leading.

biomass at the field scale, achieving wide-
spread and broad improvements at re-
gional/national scales - so that meaningful
levels of mitigation can be achieved -
faces a variety of challenges. The most ob-
vious is that adopting best practices for
GHG mitigation will, in most cases, incur
additional costs to the land user, at least
in the short-term, and therefore land users
will need to be compensated to secure
their participation. Agricultural soils have
been largely excluded as mitigation options
within the Clean Development Mechan-
ism (CDM) 1 and the Kyoto Protocol (KP)
system, although there is growing interest
for inclusion of agricultural options in
several voluntary market registries, as well
as compliance markets in Australia and
California. In order to realize a greater par-
ticipation of agriculture in climate change
mitigation, further progress is needed in
emissions quantification, as well in meeting
common GHG accounting standards that
ensure that emission reduction and seques-
tration are real and verifiable. A brief discus-
sion of these issues is given below, and the
reader is referred to other chapters for a
more in-depth treatment.
For SOC accounting, well-developed
methods exist to measure SOC stocks and
have been applied routinely for many decades.
Automated dry combustion soil C analysers
are highly accurate and, with proper labora-
tory techniques, the error in estimating the
SOC contents of a soil sample is small. How-
ever, the relative scarcity of well-equipped
laboratories in developing countries is an
impediment. Near- or mid-infrared spectros-
copy is another method under development
that has considerable promise, particularly
in developing countries (Brunet et al ., 2007),
and it has the potential for significant reduc-
tions in cost and increased sample through-
put, if adequately calibrated (Kamau-Rewe
et al ., 2011).
The issue with relying on direct
measurements for soil C accounting is not
a lack of technology per se (as is some-
times believed), but rather cost and prac-
ticality. Because SOC exhibits significant
spatial variability at field scales, and
changes in stocks relative to background

Issues and Barriers to Implementing
Agricultural C Sequestration and
GHG Reductions

While a variety of agronomic practices
have been shown to reduce GHG emis-
sions and/or sequester C in soils and