Effects Of Different Fertilizer Treatments On Nitrous Oxide Emission And GHGIs From Spring Maize Field

Nitrous oxide is one of the 3 most important greenhouse gases which cause greenhouse effect. Maize production inevitably generates nitrous oxide emissions which contribute to global warming. Agricultural managements and environment factors, especially fertilization were major management measures during maize growing season, which influenced nitrous emission directly. It was well known that urea, sulfur coated urea and dicyandiamide were typical kinds of chemical nitrogen fertilizer at present. The effect of the 3 nitrogen fertilizers mentioned above on nitrous oxide emission,grain yield and economic benefit was investigated to evaluate their potential of GHGs reduction and grain yield promotion, this study is also very important for the development of low-carbon maize production and the mitigation research of global warming.Taking spring maize as the project, 4 different fertilization treatments are: urea treatment(U); sulfur coated urea(SCU); urea added with dicyandiamide treatment(UDD)and non-fertilizer(CK). Static chamber and gas chromatography(GC) system was used to continuously monitor N2 O emission from maize cropland during 2009-2013, environment factors and soil properties were monitored simultaneously.Variation and characterization of N2 O emission, grain yield promotion and economic benefit of each treatment were analyzed comprehensively. Then, effective mitigation fertilization managements were selected considering yield, GHG emissions, and farmers income. The results showed as follow:(1) N2 O emission flux in different fertilizer treatments had an obvious seasonal variation law during maize cropping. Emission peaks mainly appeared when rainfall happened after fertilization. The emission peaks of SCU and UDD usually appeared 1-2 days latter than U. Average N2 O emissions from fertilization of 4 years ranked as: U>UDD>SCU>CK. SCU and UDD fluctuated smoother than U on daily N2 O flux, decreasing 36.8% and 27.8% N2 O emission, respectively.(2) Emission fluxes increases significantly when soil temperature higher than 20.0℃, WFPS higher than 60.0% at 5cm of soil layer..(3) There was very significant positive correlation between ammonium nitrogen content and N2 O emission of each treatment(P<0.01), but no significant correlation was observed between nitrate nitrogen content and N2 O emission of any treatment. N2 O mainly generates due to Nitrification.(4) SCU and UDD increased yield and net income by 15.6% and 5.6% while increased maize grain yield by 13.6% and 5.6% than U on average, respectively. They can be recommended as options for maize production. However, nitrogen fertilization application in this research was slightly less than requirement, which would decrease on maize grain yield.(5) Total Greenhouse Gas(GHG) emissions from different treatments ranged from 2.26 t/(hm2·a) to 2.89 t/(hm2·a), fertilizers made the greatest contribution to total GHG. Reducing unfavorable fertilization and N2 O emission is the key to decreasing GHG. The carbon footprints, Greenhouse gas Intensity(GHGI) of maize production and GHGI of economic benefit were all ranked as U>UDD>SCU. Compared with urea treatment, sulfur coated urea could reduce GHG emission per unit of yield and per 10,000-yuan net output by 19.5% and 23.3% respectively, while urea added with dicyandiamide treatment could reduce GHG emission per unit of yield and per 10,000-yuan by 12.5% and 16.0% respectively.