Agriculture Reference
In-Depth Information
contribution towards the conservation and
protection of ecosystems. Of the many ser-
vices provided by ecosystems, soil carbon
sequestration and biomass carbon potential
are examples of ones that have been more
ambitious to date, as carbon markets have
been already been established.
Among the properties that most influ-
ence soil quality is the carbon content,
which is affected strongly by agricultural
management. Hence, appropriate soil man-
agement and the induced changes in soil
carbon stocks are critical aspects when an
agricultural productive scenario is con-
sidered. It is well recognized that under ap-
propriate production scenarios, agriculture
could impact much less in neighbouring
ecosystems, and the possible disservices
caused by its externalities could be minim-
ized. Recently, agricultural systems have
been envisioned as providing similar ser-
vices as ecosystems in addition to the prod-
ucts normally associated with agriculture,
which results in a win-win situation.
The challenge of modern agriculture is
that it should provide goods as well as eco-
system services such as climate regulation,
hydrological services, greenhouse gas (GHG)
mitigation and the improvement of bio-
diversity (GBEP, 2011). As many authors
have indicated, all these aspects are directly
related to soil organic carbon (SOC). Here,
we present some results pointing to the
benefits of maintaining or building up soil
carbon levels in Latin America.
generating approximately
27,670
million
litres (Ml) (CONAB, 2011).
Residue deposition in no-burning har-
vest areas is equivalent to 15% of the dry
matter productivity of sugarcane, with a
mean value of 13.9 Mg of dry matter ha
-
1
year
-
1
(Campos, 2003). No-burning harvest
systems have several benefits: for instance,
higher crop longevity and lower costs for re-
newing areas; recycling and gradual release
of nutrients by straw decomposition; de-
crease in gas emissions; and less nutrient
losses (Canellas
et al
., 2003). There is also
improvement of physical soil conditions,
such as moisture retention, which is espe-
cially important during drought periods
(Resende
et al
., 2006), increase in soil aggre-
gate stability (Szakács, 2007; de Luca
et al
.,
2008) and improvement in soil structure,
mainly in sandy soils with an original low
level of soil carbon (C) (de Luca
et al
., 2008).
Higher organic matter levels in soils
improve chemical and physical soil proper-
ties, as discussed above, and also contribute
to the mitigation of global warming by in-
creasing soil C stocks. Sugarcane crops
without burning accumulate more organic C
in the soil than those harvested with fire
(20% more C in 0-5 cm and 15% more in
0-10 cm soil depth). The main difference in
organic carbon levels between the two sys-
tems occurs in the 0-
2
μm fraction, where
there is 35% more C under no-burning man-
agement (Razafimbelo
et al
., 2006), indicat-
ing the stabilization of the accumulated C.
This was also shown by higher humification
indexes of soil organic matter (SOM) (Panos-
so
et al
., 2011) in no-burn sugarcane. SOM
under this management has up to four times
more C of aromatic compounds and less C
of carboxylic groups (Canellas
et al
., 2003).
However, the effect of the harvest manage-
ment system on the quality of soil C seems
to occur slowly. The results reported by
Canellas
et al
. (2003) occurred
55
years after
the adoption of green harvest, while Czycza
(2009), considering a period of
12
years
without burning, did not observe differences
in carboxylic and phenolic group concen-
trations of humic acids due to sugarcane
harvest management. Czycza (2009) also
compared
12-
and
19-
year-old areas and
Burned Versus Green
Harvested Sugarcane
Brazil is the main sugarcane producer
in the world; with nearly twice the har-
vested area and almost 2.5 times more
production than India, which ranks se-
cond (FAOSTAT, 2012). In 2010, the sug-
arcane harvested area in Brazil was more
than
8
million hectares (Mha) and produc-
tion close to 625 million tonnes (Mt), an
increase of 3.4% compared with the pre-
vious year. Around 54% of sugarcane pro-
duced in Brazil is for ethanol production,
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