From Potential to Implementation: An Innovation Framework to Realize the Benefits of Soil Carbon - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 49

position regarding the role of mineral and
organic fertilizers (Manlay et al ., 2007).
Knowledge of the biogeochemical cycles
of carbon and nitrogen advanced rapidly
during the beginning of the 19th century
when the role of microorganisms in the
turnover of carbon and nitrogen was dis-
covered. The appreciation of the integrative
function of SOM was initiated with further
insights into the role of clay in forming or-
ganomineral complexes and aggregate for-
mation. This cumulated in the works of
Waksman, who characterized humus as a
'source of Human wealth on this planet'
(Waksman, 1938).
The widespread industrial production
of chemical fertilizers improved crop yields
tremendously, but also led to serious envir-
onmental degradation. The demand for food
from the explosively growing cities created
new carbon pathways from the rural pro-
duction areas to the urban centres of con-
sumption, breaking the traditional approaches
of recycling organic matter. The dust bowl
of the 1930s painfully showed the unin-
tended consequences of new agricultural
practices that were unsustainable. Severe
drought combined with the conversion of
grasslands to cropland, simplified crop rota-
tion and deep ploughing of virgin soil con-
tributed to the destruction of soil aggregates,
loss of organic matter and wind erosion of
topsoil, illustrating the significant relation-
ships between soil, land surface and cli-
mate. In the 1940s, the environmental deg-
radation legacy of the industrial era led to
renewed interest in SOM research for im-
proving understanding of nutrient cycling
and ecosystem functioning. The emergence
of ecosystem science, founded on the con-
cept of energy and nutrient cycling, gave
momentum to a more holistic approach to
material and life sciences.
It was during the Industrial Revolution
that the 'greenhouse gas effect' was pro-
posed as a mechanism for controlling the
temperature of the planet (Arrhenius, 1896;
Callendar, 1938). The idea was controver-
sial until Keeling et al . (1976) observed a
rapid rise of CO 2 concentration in the at-
mosphere. The recognition of the linkage
between atmospheric and soil carbon came

even later when the exchange between these
carbon stocks was identified.
With the Millennium Ecosystem As-
sessment (MA, 2005), ecosystem services
became one of the core issues of modern
ecology. Ecosystem services comprise the
wide range of benefits that humans derive
from ecosystems and provide a conceptual
framework for sustainable management
(MA, 2005). The MA distinguishes between
provisioning, regulating, supporting and
cultural services. Soils fulfil a wide variety
of environmental services as a foundation
for biomass production, a filter and buffer
for water, an archive of natural and human
history and an important store of carbon. In
1997, Daily et al . suggested six major ser-
vices associated with soil organic matter
(SOM), including physical support, water
buffering, nutrient retention, waste/OM re-
cycling, soil fertility renewal and regulation
of element cycling. Schmidt et al . (2011)
mentioned soil fertility, water quality, ero-
sion resistance and climate mitigation as
important ecosystem services related to
SOM. Soil biodiversity is seen as an import-
ant prerequisite for providing high-quality
soil ecosystem services (Brussaard et al .,
2007). The concept of ecosystem services
facilitates the assessment of the impacts of
management (e.g. past innovations such as
mineral fertilizer use) in an integrated, hol-
istic way.

What Ought to be Done?
A Summary of Best Practices

Figure 4.1 presents a conceptual model
change in SOC over time based on the 'soil
carbon transition curve' (Chapter 3, this
volume). It shows the decline in SOC dur-
ing conventional agricultural land use and
its degree of restoration depending on the
chosen carbon sequestration techniques. As
a result of unsustainable land-use practices
or disturbance (Fig. 4.1 , arrow 1), the con-
tent of soil organic carbon will decrease
substantially in conventional agricultural
systems until a lower stable situation, where
C input ~ C output , is reached ( Fig. 4.1 , arrow 2)