Low Carbon Technologies for Agriculture

Abstract

Today, global warming is the most prominent environmental issue before the humanity. It is caused by the increase in concentration of greenhouse gases (GHGs) in the atmosphere. The GHGs, viz. carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O), trap the outgoing infrared radiations from the earth’s surface and thus raise the temperature. The accumulation of GHGs in atmosphere and the consequent rise in earth’s temperature is termed as ‘greenhouse effect’. According to a world agency, Inter-Governmental Panel on Climate Change (IPCC), due to greenhouse effect the global mean annual temperature was recorded higher by 0.40-0.76 °C at the end of the 20th century than was at the end of the 19th century (IPCC, 2007). This agency has projected a rise of 1.1 to 6.4 °C in temperature by the end of the 21st century. The global warming is leading to several other regional and global changes such as rainfall, soil moisture and sea level. Among different sources, agricultural soil is the major contributor to greenhouse effect. Globally, agriculture accounts for 54% of anthropogenic methane and 58% of nitrous oxide emissions. In soils, methane is produced during microbial decomposition of organic matter under anaerobic conditions. Rice fields submerged with water, therefore, are the potential source of methane. Continuous submergence, higher organic C content and use of organic manure in puddled soils enhance methane emission. Burning of crop residues also contributes to the global methane budget. Enteric fermentation in ruminants is another major source of methane. Nitrogenous fertilizers are the source of N2 O in fertilized soils, whereas the indigenous N contributes to its release in unfertilized soil. Soil water content and the availability of carbon enhance the production of N2 O, provided a suitable nitrate source is available. Generally, increase in N2 O emission is observed following irrigation and precipitation. Burning of crop residues also contributes to the global N2 O budget.