Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 318

silage than by feeding dry corn. In China, the
proportion of silage and ammoniated straw feed-
ing is only 44 % at present. Feed saving, improve-
ment of feed conversion effi ciency, and reduction
in CH 4 emission can all be achieved by constantly
increasing the proportion of silage to ammoni-
ated straw. The potential for CH 4 emission reduc-
tions is also tremendous.

hence, soil carbon storage (Conant et al. 2001 ).
Adding nitrogen, however, often stimulates N 2 O
emissions (Conant et al. 2005 ) thereby offsetting
some of the benefi ts. Irrigating grasslands, simi-
larly, can promote soil carbon gains (Conant
et al. 2001 ). The net effect of this practice, how-
ever, depends also on emissions from energy use
and other activities on the irrigated land
(Schlesinger 1999 ).

13.2.4 Grazing Land Management

13.2.4.3 Nutrient Management
Practices that tailor nutrient additions to plant
uptake, such as those described for croplands,
can reduce N 2 O emissions (Dalal et al. 2003 ).
Management of nutrients on grazing lands, how-
ever, may be complicated by deposition of feces
and urine from livestock, which are not as easily
controlled nor as uniformly applied as nutritive
amendments in croplands (Oenema et al. 2005 ).

Grazing lands occupy much larger areas than
croplands (FAOSTAT 2006 ) and are usually man-
aged less intensively. Several management tech-
niques can be identifi ed that will support climate
change mitigation efforts:
• Grazing intensity management
• Increased productivity
• Nutrient management
• Fire management
• Species introduction
The total mitigation potential of grazing land
management techniques is substantial.

13.2.4.4 Fire Management
On-site biomass burning (not to be confused with
bioenergy, where biomass is combusted off-site
for energy) contributes to climate change in sev-
eral ways. Firstly, it releases GHGs, notably CH 4
and, and to a lesser extent, N 2 O (the CO 2 released
is of recent origin, is absorbed by vegetative
regrowth, and is usually not included in GHG
inventories). Secondly, it generates hydrocarbon
and reactive nitrogen emissions, which react to
form tropospheric ozone, a powerful GHG. Thirdly,
fi res produce a range of smoke aerosols which can
have either warming or cooling effects on the
atmosphere; the net effect is thought to be positive
radiative forcing (Venkataraman et al. 2005 ).
Fourth, fi re reduces the albedo of the land surface
for several weeks, causing warming (Beringer
et al. 2003 ). Finally, burning can affect the pro-
portion of woody versus grass cover, notably in
savannahs, which occupy about an eighth of the
global land surface. Reducing the frequency or
intensity of fi res typically leads to increased tree
and shrub cover, resulting in a CO 2 sink in soil
and biomass (Scholes and van der Merwe 1996 ).
This woody plant encroachment mechanism
saturates over 20-50 years, whereas avoided CH 4
and N 2 O emissions continue as long as fi res are
suppressed.

13.2.4.1 Grazing Intensity
The intensity and timing of grazing can infl uence
the removal, growth, carbon allocation, and fl ora
of grasslands, thereby affecting the amount of
carbon accrual in soils (Conant et al. 2001 , 2005 ).
Carbon accrual on optimally grazed lands is often
greater than on ungrazed or overgrazed lands
(Liebig et al. 2005 ). The effects are inconsistent,
however, owing to the many types of grazing
practices employed and the diversity of plant
species, soils, and climates involved (Derner et al.
2006 ). The infl uence of grazing intensity on emis-
sion of non-CO 2 gases is not well-established,
apart from the direct effects on emissions from
adjustments in livestock numbers.

13.2.4.2 Increased Productivity
(Including Fertilization)
As for croplands, carbon storage in grazing lands
can be improved by a variety of measures that
promote productivity. For instance, alleviating
nutrient defi ciencies by fertilizer or organic
amendments increases plant litter returns and,