Environmental Engineering Reference
In-Depth Information
10.2 SOC Changes in Relation to Cropping Systems
and Management in Mediterranean Semi-arid Areas
Understanding SOC changes in relation to ecosystem management is needed to
develop C accounting models and future policies, oriented at attenuating the GHG
warming effect. In arable lands, optimum levels of SOC could be mainly managed
through crop rotations, tillage methods, inorganic fertilizers and organic manures
(Kundu et al.
2007
; Lal
2004
). To mitigate the universally admitted deleterious
effect of conventional cropping on SOC, several studies suggested to increase the
frequency in the rotation of high biomass production and crops with elevated C/N
ratio residue, as well as fertilize, apply organic manure, irrigate, and/or reduce
tillage intensity (Su et al.
2006
; Studdert and Echeverria
2000
; Lal
2004
; Sainju
et al.
2006
; Morari et al.
2006
). However, the magnitude in SOC change following
such usually recommended practices is soil and site specific. The potential of dif-
ferent eco-regions of the world to sequester C is in fact climatic dependent, being
higher in tropical and temperate regions where crop growth conditions are more
favourable.
The Italian territory encompasses a wide range of orographic and climatic
conditions, ranging in latitude from about 47° to 36°N. In particular, most of the
coastal areas of central and southern Italy, including the major islands, are affected
by a typical Mediterranean climate. In this area, the interaction between land
management and climate change is particularly critical due to frequently severe
drought conditions and soils, which are inherently low in C and more susceptible
to degradation.
The Island of Pianosa (see Sect.
2.2.18
) is an interesting case study for SOC
evolution related to land use change, as it was intensively cultivated for sev-
eral centuries and completely abandoned since the end of 1990s. Vaccari et al.
(
2012
) conducted a medium-term campaign of CO
2
fluxes measurement with
Eddy Covariance from 2002 to 2009, showing that the abandoned ecosystem
was able to rapidly recover the SOC depleted during agricultural exploitation by
about 30 % above the 1990s value. Furthermore, the authors calibrated the SOC-
ecosystem model Century (Parton et al.
1988
) with the measured data, in order
to perform some scenario analysis. The results suggested that re-cultivation of
these soils may potentially cause a SOC loss ranging from 41 to 58 t C ha
−
1
in
the next 90 years, if appropriate soil conservation management practices are not
implemented.
The interaction between tillage practices (conventional vs. no-tillage) with
different rates of N fertilizer was measured and modelled by (de Sanctis et al.
2012
) in another typical Mediterranean environment: the experimental farm of
University of Sassari in Agugliano (4821339 m N, 368026 m E). In this study the
DSSAT model satisfactorily matched the measured data, showing SOC increase
with no till and moderate to high N fertilization rates compared to conventional
tillage. The application of these techniques suggested a steadily increase of SOC
over a 50-year period at a rate of about 0.3 t ha
−
1
y
−
1
.
