Researchers at the non-profit Environmental Defense Fund reveled that management of irrigated rice paddies may lead to double-fold emission of greenhouse gases
Rice is a major staple food for majority of the population worldwide. However, the management of irrigated rice paddies has significant effects on the climate. The researchers at the non-profit Environmental Defense Fund observed the emissions of nitrous oxide, which is a long-lasting atmospheric pollutant and is more potent compared to methane or carbon dioxide. Nitrous oxide rises when rice fields are allowed to dry before being wetted again. The process of intermittent flooding commences when water falls below the soil level several times annually. The process is encouraged by some agricultural organizations affiliated with the United Nations Food and Agriculture Organization for saving water and reducing methane, which is another major greenhouse gas emitted by rice paddies. However, no data is available about the number of implications of the process done by farmers.
The frequent wetting and drying of soil offers an ideal environments for microbes that produce nitrous oxide, whereas methane is produced by microbes that require soils to be submerged in water. According to the researchers, it is generally assumed that majority of irrigated farms worldwide are continuously flooded and such continuous flooding in farms reduces the production of nitrous oxide. However, not all farms are continuously flooded, which suggests that total climate impact of rice farming has been significantly underestimated. According to the research the amount of unaccounted-for nitrous oxide global emissions from rice may be as high as the annual climate pollution from about 200 coal power plants.
The study was conducted across five intermittently flooded rice fields in India and the researchers stated that nitrous oxide emissions could be 30-45 times higher than reported under continuous flooding, in India. The calculated nitrous oxide per hectare was around three times higher than previous reports. The researchers suggest shallow flooding of paddy fields, which can maintain the water level within five to seven centimeters of the soil level. The research was published in the Proceedings of the National Academy of Sciences on September 10, 2018.