Organic Carbon Sequestration Potential and the Co-Benefits in China’s Cropland - Principles of Sustainable Soil Management in Agroecosystems - page 515

(2006), Feng et al. (2006) and Li et al. (2007) demonstrated also enhanced diversity
of weeds in the field and the seed bank in soil with SOC accumulation under the
good fertilization schemes. Using soil samples from the same experiment, a study
by Han et al. (2009) indicated decreased content but increased degradation of PAHs
with SOC accumulation under different fertilization practices. Thus, SOC sequestra-
tion in croplands, particularly in rice paddies, would offer multiple win-win effects
for crop productivity, mitigation of GHG emission, as well as ecosystem health in
agriculture, thus ensuring food security and sustainability of agriculture for China
(Pan and Zhao 2005).
We have developed a hypothesis as a concept model for characterizing the mutual
co-benefits of SOM's role in enhancing productivity and ecosystem functioning
(Figure 18.10). The input of OM to soil may at first act as single particulate mate-
rial, which could have chemical reactivity during the first time. With time, OM gets
into soil organomineral complexes through physical and chemical binding, which
could further form microaggregates within which soil microbes could colonize. The
microaggregates could then be transformed into macroaggregates, which offer a
wide range of microhabitats for different species and communities of soil organ-
isms. In this way, a functional entity is developed with mutual interaction of mineral,
chemical, biological, and ecological forces. Therein, the soil processes and function-
ing could be magnified to enhance soil capacity for nutrient, moisture, and biotic
conservation. Therefore, the soil activity with accumulation of SOM in topsoil would
be a linear response not to the content of SOM but to the interaction of SOM with soil
attributes. In such a framework, soil crop productivity and ecosystem functioning
can be harmonized for ensuring sustainability.

Pedological
and ecological

Physical, chemical
and microbiological

(a)

Physical and
chemical

Microaggregate

(b)

Functional aggregates

Chemical

500 nm

Microaggregates

50 nm

Organomineral
complex

SOM particulate

Increase in scale and dimension

FIGURE 18.10 Concept model of the role of SOM in enhancing ecosystem functioning.