Geoscience Reference
In-Depth Information
place or a higher water table be re-established. If not, emissions
can be reduced to some extent by avoiding deep ploughing, dis-
couraging row crops and tubers and maintaining a shallower
water table (Freibauer et al., 2004).
Resto ration of
degraded lands
Degraded agricultural lands can be partially restored and car-
bon storage can be improved by re-vegetation, nutrient amend-
ments, application of organic substrates (manures, biosolids,
composts), minimum/zero tillage, retaining crop residues and
water conservation (Batjes, 1999; Bruce et al., 1999; Lal,
2001a,b, 2003, 2004b; Olsson and Ardö, 2002; Paustian et al.,
2004; Foley et al., 2005). Where these practices involve higher
nitrogen amendments, the benefits of carbon sequestration may
be partly offset by higher N
2
O emissions (Smith et al., 2007a).
Livestock
management
The practices for reducing CH
4
and N
2
O emissions from live-
stock (cattle and sheep) rearing are categorised as improved
feeding practices, use of specific agents or dietary additives and
long-term management changes and animal breeding (Monteny
et al
.,
2006; Soliva et al., 2006).
Improved feeding practices:
Improving pasture quality (in
less developed regions to improve animal productivity), replac-
ing forages with concentrates, supplementing certain oils or
oilseeds to the diet and optimising protein intake (reduce N
excretion) can reduce CH
4
and N
2
O emissions, but may increase
daily methane emissions per animal (Blaxter and Claperton,
1965; Leng, 1991; Johnson and Johnson, 1995; McCrabb et al.,
1998; Machmüller et al., 2000; Phetteplace et al., 2001; Lovett
et al., 2003; Beauchemin and McGinn, 2005; Clark et al., 2005;
Alcock and Hegarty, 2006; Jordan et al., 2006a-c).
Specific agents and dietary additives:
Dietary additives fed
to the animals can suppress methanogenesis to reduce CH
4
emissions. These are ionophores (antibiotics—banned in the
EU); halogenated compounds (inhibit methanogenic bacte-
ria—can have side effects such as reduced intake); novel plant
compounds such as condensed tannins, saponins and essential
oils (side effect—reduced digestibility); probiotics (yeast cul-
ture); propionate precursors (fumarate or malate—expensive);
vaccines (against methanogenic—not yet commercially avail-
able) and bovine somatotropin and hormonal growth implants
(Wolin et al., 1964; Benz and Johnson, 1982; Rumpler et al.,
1986; Johnson et al., 1991; Bauman, 1992; Schmidely, 1993;
Van Nevel and Demeyer, 1995, 1996; McCrabb, 2001; Newbold
et al., 2002; Lila et al., 2003; Pinares-Patiño et al., 2003;
McGinn et al., 2004; Wright et al., 2004; Newbold et al., 2005;
