Geoscience Reference
In-Depth Information
Agronomy:
Improved agronomic practices such as using
improved crop varieties, extending crop rotations especially
with perennial crops (produce more below ground carbon),
rotation with legumes, growing 'cover' or 'catch' crops, effi-
cient fertiliser/nutrient, pesticides and other input management
and avoiding or reducing fallow which not only increases yields
but also increases soil carbon storage through higher residue
production (Follett, 2001; Izaurralde et al., 2001; West and
Post, 2002; Lal, 2003, 2004a; Barthès et al., 2004; Freibauer
et al., 2004; Paustian et al., 2004; Smith, 2004a,b; Alvarez,
2005). However, N benefits (also with legume-derived N) can
be offset by emissions of higher soil N
2
O and CO
2
from fer-
tiliser manufacture (Schlesinger, 1999; Pérez-Ramírez et al.,
2003; Robertson, 2004; Gregorich et al., 2005; Rochette and
Janzen, 2005). The catch or cover crops can extract available N
unused by the preceding crop, thereby reducing N
2
O emissions
(Barthès et al., 2004; Freibauer et al., 2004).
Nutrient management:
Crops cannot always use applied
nitrogen that emits out of the soil as N
2
O efficiently (Galloway
et al., 2003, 2004; Cassman et al., 2003; McSwiney and
Robertson, 2005). Nitrogen-use efficiency can be improved
by reducing leaching and volatile losses, applying the precise
crop need, using slow/controlled-release forms or nitrification
inhibitors (slowing the microbial processes leading to N
2
O for-
mation), applying just prior to plant uptake (least susceptible to
loss), placing precisely for accessibility to roots and avoiding
excess application during immediate plant requirements, which
will directly reduce N
2
O emissions and indirectly reduce GHG
emissions from N fertiliser manufacture (Cole et al., 1997;
Schlesinger, 1999; Dalal et al., 2003; Paustian et al., 2004;
Robertson, 2004; Monteny et al., 2006).
Tillage/residue management:
Minimal or zero tillage gen-
erally results in soil carbon gain and reduced CO
2
and N
2
O
emissions through enhanced decomposition of retained crop
residues and erosion due to less disturbance of soil and less
energy use (Marland et al., 2001, 2003b; West and Post, 2002;
Cassman et al., 2003; Cerri et al., 2004; Smith and Conen, 2004;
Alvarez 2005; Gregorich et al., 2005; Helgason et al., 2005; Li
et al., 2005; Madari et al., 2005; Ogle et al., 2005; Koga et al.,
2006). Residue burning should be avoided to prevent emissions
of aerosols and GHGs generated from fire (Cerri et al., 2004).
Water management:
Supplementary irrigation provides water
to 18% of the world's cropland (Anonymous, 2005a). Improving
the efficiency of this irrigation system supplementary through
delivery and drainage management along with further extension
