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Submitted to: MethodsX
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/23/2017 Publication Date: 7/7/2017 Publication URL: https://handle.nal.usda.gov/10113/5763049 Citation: Sainju, U.M. 2017. Nitrogen balance in agroecosystems. MethodsX. 4:199-208. doi:10.1016/j.mex.2017.06.001. Interpretive Summary: A major nutrient applied in large amounts to sustain agricultural productivity and crop quality is nitrogen. Although nitrogen fertilization can increase crop yields, excessive application of nitrogen fertilizers can have detrimental effects on soil and environmental quality, such as increased soil acidification, nitrogen leaching, and emissions of nitrous oxide, a highly potent greenhouse gas that contributes to global warming. Crops can use only 50 to 60% of applied nitrogen, while the remaining portions result in the accumulation of residual soil nitrogen that comprised mainly of nitrate-nitrogen after crop harvest. Such residual nitrate-nitrogen can be lost through leaching, denitrification, surface runoff, soil erosion, and nitrous oxide emissions. An increase in soil nitrogen storage by using improved management practices can reduce N losses through leaching, volatilization, denitrification, surface runoff, erosion, and nitrous oxide emissions compared with traditional management practices. Nitrogen balance in agroecosystems provides a quantitative framework of nitrogen inputs and outputs and retention in the soil that examine sustainability of agricultural productivity and soil and environmental quality. Nitrogen inputs include nitrogen additions from manures and fertilizers, atmospheric depositions including precipitation and dry deposition, irrigation water, and biological nitrogen fixation. Nitrogen outputs include nitrogen removal in crop grain and biomass and nitrogen losses through leaching, denitrification, volatilization, surface runoff, erosion, gas emissions, and during plant senescence. Nitrogen balance, which is the difference between nitrogen inputs and outputs, can be reflected in changes in soil total (organic + inorganic) nitrogen from the beginning to the end of the experiment due to nitrogen immobilization and mineralization. While increased soil nitrogen retention may improve soil quality by increasing crop yields and reducing nitrogen fertilization rate, increased nitrogen losses through leaching and gas emissions (primarily nitrous oxide emissions) deteriorate water and air quality. This chapter discusses measurements of all inputs and outputs of nitrogen as well as changes in soil nitrogen storage during the course of the experiment for calculating nitrogen balance that will be used to evaluate the sustainability of agroecosystems. Technical Abstract: Nitrogen balance in agroecosystems provides a quantitative framework of N inputs and outputs and retention in the soil that examine sustainability of agricultural productivity and soil and environmental quality. Nitrogen inputs include N additions from manures and fertilizers, atmospheric depositions including precipitation and dry deposition, irrigation water, and biological N fixation. Nitrogen outputs include N removal in crop grain and biomass and N losses through leaching, denitrification, volatilization, surface runoff, erosion, gas emissions, and during plant senescence. Nitrogen balance, which is the difference between N inputs and outputs, can be reflected in changes in soil total (organic + inorganic) N from the beginning to the end of the experiment due to N immobilization and mineralization. While increased soil N retention may improve soil quality by increasing crop yields and reducing N fertilization rate, increased N losses through leaching and gas emissions (primarily N2O emissions) deteriorate water and air quality. This chapter discusses measurements of all inputs and outputs of N as well as changes in soil N storage during the course of the experiment for calculating N balance that will be used to evaluate the sustainability of agroecosystems. |
