N2O Emissions Essay

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The N2O emissions depend upon the type of crop such as, in a study by Smith et al. (1998) comparing different grassland and arable soils, it was observed that emissions were in the order of grassland as the highest followed by grassland cut for conservation, potatoes and lowest from cereal crops. There was high variation in emissions from one year to another depending on rainfall at the time of fertilization. There was exponential relationship between N2O flux and water-filled pore space and temperature where soil N was not limiting factor (Smith et al., 1998). Exponential increases in N2O flux was observed with increasing soil water-filled pore space, temperature and increase in soil mineral N content. It differs with the type of crop, type of soil, weather patterns and agricultural management practices (Dobbie et al., 1999). In Alberta, emissions were high when N fertilizer was applied in fall as compared to that applied in spring. Straw removal at harvest in fall increased N2O emissions when fertilizer was applied in fall, but emissions decreased when fertilizer was not applied. Fall plowing also increased N2O emissions compared to spring plowing or direct seeding (Hao et al., 2001). In silty loam soil, the highest N2O flux was observed from organically managed soil after manure and legume cover crop incorporation and in conventionally managed soil after inorganic N fertilizer application. Elevated N2O emissions occurred at a Water-filled pore space of more than 60% and lasted less than 2 days after wetting (Burger et al., 2005). According to a review by Barnard et al. (2005), in field and laboratory N addition significantly increased N2O emissions due to gross and net in nitrification, but the effect of N addition on field N2... ... middle of paper ... ...he total world fiber use. In the year 2011, the U.S. (15,573,000 pound bales) was the third largest producer of cotton in the world after China (33,100,000 pound bales) and India (27,500,000 pound bales), and accounts for 14% of the total world’s cotton production (NCCA, 2011). In addition, U.S. is the largest exporter of cotton with 11,714,000 pound bales of cotton exported in the year 2011(NCCA, 2011). Furthermore, in the U.S., California’s SJV is among the major producers of cotton in the U.S. In the last decade, the total area under cotton in California was decreasing, but now the downward trend in plantings is shifting with the increase in acreages from 76, 890 ha in 2009, to 123,429 ha in 2010. This upswing continued in 2011 with total planting of 182,109 ha. In California cotton is also grown in the Palos Verde valley and Sacramento Valley (NASS USDA, 2012).

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