A review of the N2O-N emission from crop residues was conducted based on new data published during the last decade. The result indicated that factors as type of crop, biochemical quality of residues, agricultural management, climate and season of the year, soil properties and soil moisture play a significant role in the rate of N2O-N emissions. An emission factor (EF) equal to 1.055% of N applied in plant residues – derived from a simple linear regression of emitted N2O-N (kg ha−1) on N applied in crop residues (kg ha−1) – represent an estimate that explains about 60% of emission variations. However, the EF of N applied in plant residues is not a constant but a variable coefficient that depends on environmental and management variables. The following two linear models – that estimate emitted N2O-N (kg ha−1) as a function of the variables N (kg ha−1) applied in plant residues (NPR), rain (mm), temperature (°C) and temperature2(°C2) – were fitted to the dataset with 45 observations obtained from the reviewed literature.
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\begin{document}$$\hskip1.5pc\hbox{N}_{2}\hbox{O}\hbox{-}\hbox{N}=-4.154+0.00955\hbox{ NPR}+1.7278\hbox{ ApM}+0.003996\hbox{ Rain }+0.6242\hbox{ Tem }-0.0230\hbox{ Tem}^{2}$$\end{document}and
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\begin{document}$$\hbox{N}_{2}\hbox{O}\hbox{-}\hbox{N}= 0.6535 + [-0.0404 + 0.0078\hbox{ ApM }+ 0.000044\hbox{ Rain }+ 0.00567\hbox{ Tem }-0.0001975\hbox{ Tem}^{2}]\hbox{ NPR }$$\end{document}
Both models provided almost equally good statistical fit to the data, with R2=0.832 and R2=0.829, respectively, and most regression coefficients being significant at \documentclass[12pt]{minimal}
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\begin{document}$$P < 0.01$$\end{document}. Because of its internal structure, the second model is more appealing as it represents N2O-N emission as a transformation that is affected by management and environmental variables. The following expression – that correspond to the quantities in the square bracket at the right hand side of the second model – is the coefficient for the variable N applied in crop residues, and represent the emission factor as a function of application method of plant residues, rain, temperature and temperature2.
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\begin{document}$$\hskip3.5pc\hbox{EF }=-0.0404+0.0078\hbox{ ApM }+0.000044\hbox{Rain }+0.00567\hbox{ Tem }- 0.0001975\hbox{ Tem}^{2}$$\end{document}
