Greenhouse Gases from Crop Fields

A rapid increase in atmospheric concentrations of the three main anthropogenic greenhouse gases (GHGs), like carbon dioxide (CO

2

), methane (CH

4

) and nitrous oxide (N

2

O), is evident from measurements taken over the past few decades as well as ice-core records spanning many thousands of years (IPCC 2007). The global increases in CO

2

concentration are due to fossil fuel and land-use change, while those of CH

4

and N

2

O are primarily from agriculture (Cole et al. 1997; IPCC 2007). Despite large annual exchanges of CO

2

between the atmosphere and agricultural lands, the net flux is approximately balanced (IPCC 2007). Arable and permanent crops occupy 1,540Mha in 2003 which is about 12% of the Earth’s land surface (FAOSTAT 2006). In 2005, agriculture contributes about 47 and 58% of total anthropogenic emissions of CH

4

and N

2

O, respectively, with a wide range of uncertainty in the estimates of both the agricultural contribution and the anthropogenic total.