Mitigating Greenhouse Gas Emission from Agriculture

Radiative forcing of Earth’s atmosphere is increasing at unprecedented rates, largely because of increases in the concentrations of atmospheric trace gases, mainly carbon dioxide (CO

2

), methane (CH

4

) and nitrous oxide (N

2

O) – collectively known as greenhouse gases (GHG). Concentrations of CO

2

, CH

4

and N

2

O have increased markedly as a result of human activities since 1750 and now far exceeded pre-industrial values as determined from ice cores spanning thousands of years (Table 15.1). The atmospheric concentrations of CO

2

and CH

4

in 2005 have exceeded the natural range over the last 650,000 years (IPCC 2007). The global atmospheric concentration of CO2 has increased at an annual growth rate of 0.5%, while that of CH

4

at 0.6% and nitrous oxide at 0.25%. Agriculture plays a major role in the global fluxes of each of these gases and is considered as one of the major anthropogenic sources (Fig. 15.1). Agriculture comprises several activities, contributing to GHG emissions and globally, the most significant activities identified include (i) deforestation and other land-use changes as a source of CO

2

, (ii) rice-based production systems (including rice-wheat rotation) as sources of CH

4

and N

2

O (and also source of CO

2

due to burning of agricultural residues) and (iii) animal husbandry as a source of CH

4

.