Emission, effects and mitigation of greenhouse gases (GHGs) in agriculture

The main sources of Green House Gases (GHGs) emission are burning of fossil fuels (for industrial use,transportation, electricity etc.), clearing the land to produce wood (domestic, industrial, or crop husbandry etc.), industrial developments, energy sector and agriculture. Carbon dioxide, methane, nitrous oxide, ozone and Chlorofluorocarbons (CFCs) are the primary GHGs in our atmosphere. GHGs absorb and emit the solar radiations within thermal infrared range which is the basic cause of greenhouse effects. It is reported that since pre industrial, there is an increase of ۳۱%, ۱۵۱% and ۱۷% in CO۲, CH۴ and N۲O, respectively. Land clearing for crop husbandry is responsible for high CO۲ in atmosphere. Land clearing disturbs the soil and increases the organic matter decomposition which results in release of high quantity of CO۲. It enhances the soil erosion which limits the soil’s ability to uptake carbon. Crop husbandry includes the slash and burning the residues which further add up CO۲ in the atmosphere. Methane (CH۴) is produced as by product in several agricultural activities. Rice culture, livestock and termite mounds are the main sources of methane emissionwhile biomass burning also contributes significantly. Standing water with a lot of organic water creates anaerobic conditions where anaerobic bacteria utilize CO۲ as source of O۲ and release huge amount of methane. In traditional rice culture, rice crop is submerged for four months a year. This practice adds ۵۰-۱۰۰ million tons of methane in atmosphere and reported to be the largest anthropogenic source of methane. Termite mounds are a significant methane release process in tropics due to abundant plant residues. The bacterial activity in the animal’s stomach and intestine (particularly the cows and buffalos) is another source of methane emission (about ۱۰۰ million tonnes per year) to atmosphere. Further the decomposition of livestock wastes is another significant source of methane emission. N۲O is the third important GHG released by agriculture. Bacteria in low/zero-oxygen environments convert nitrite (NO۳) to nitrogen gas (N۲) and nitrous oxide (N۲O) under anaerobic conditions. Inorganic fertilizers and animal manure are the main source of N۲O release in the soil. Among the cereals, rice is the main staple food more than half of world population, mainly in Asia and Africa.To feed ۹ billion world population, ۲۵ % increase in rice yield is required in ۲۰۵۰. Tropics contribute ۷۵ % of world rice production. The effects of climate change are expected to be more severe in tropics. Intergovernmental Panel on Climate Change (IPCC) reported an increase in global temperature (۰.۶ °C) during last century and predicted a further increase about ۵ °C during this century. This climate change will affect the rice productivity severely due to sensitivity of critical stages of rice crop. The optimum temperatures for germination, tillering, pollination and ripening are ۱۸-۴۰ °C, ۲۵-۳۱ °C, ۳۰-۳۳°Cand ۲۰-۲۹ °C, respectively. The current temperatures are already approaching critical levels in different countries e.g. Pakistan/ India (September, October), South India (April, August), East India/Bangladesh (March–June) in subcontinent.Several researchers reported negative effects at different growth stages which resulted poor rice productivity due to low germination, poor tillering, high panicle sterility etc. Water shortage, increased soil salinity, flooding, increased risk of disease infestation and pest attack and enhanced rice-weed competition are the others outcomes of climate change. These factors will affect the rice productivity severely. To face the future challenges in rice productivity, development of tolerant varieties to environmental stresses (temperature, salinity, lodging, and drought) and biotic stresses (disease and insect-pest resistance) is only option either through hybridization or genetic transformation. Climate smart agriculture (CSA) is an integrated approach to manage landscapes, croplands, livestock, forests, and fisheries that address the interlink challenges of food security and climate change with aim to achieve simultaneously achieve three outcomes; increased productivity, enhanced resilience and reduced emissions. Emission of methane may be reduced by keep low numbers of animals with high productivity of milk and meat, establishment of rangelands for grazing, generation of biogas and biofertilizer form the animal wastes. Similarly, dry rice culture may be adopted by introducing the climate resilient varieties with tolerance to biotic and abiotic stresses. The nitric oxide emission may be reduced by intruding the organic fertilizers, optimum dose and right time for application of chemical fertilizers, increasing the soil organic matter, use of slow-release fertilizers. However, CO۲ may be managed by AGRO FORESTORY, encouraging the home gardening, rooftop gardening, urban farming etc. Last but foremost, a comprehensive awareness campaign may be initiated worldwide to raise such a generation who can be CLIMATE GUARDIANS, as mindset and attitudes would be the key elements in mitigation process.