LAUSR

Nitrogen (N) management in cropping systems needs adjustments because constraints to crop production are mostly related to high inputs and low recovery of N fertilizers. We used the DayCent model to predict regional N inputs, outputs, and balances of Swiss soils under (1) a range of N fertilizer input levels (0–300% of recommended crop-specific rates) and (2) organic fertilization, reduced tillage or cover cropping at the recommended input of N. The crops included wheat, maize, and root/tuber crops and legumes. Decreasing N inputs reduced the environmental impact by 13.5–51.3 kg N ha-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-1}$$\end{document}, but it also reduced the yield by 6.8–44.8 kg N ha-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-1}$$\end{document}. Increasing N inputs led to an increase in yield by 5.6–29.5 kg N ha-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-1}$$\end{document}, but with additional losses of 14.9–181.8 kg N ha-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-1}$$\end{document} into the environment. Harvested crop N and NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {NO}_3^{-}$$\end{document} leaching accounted for 30–59% and 27–62% of fertilizer-derived changes in total N output, respectively. Converting conventional to organic cropping led to a mean increase in soil N balance by 0.3–62.6 kg N ha-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-1}$$\end{document}. The soil N balance increased the most by using partially decomposed organic fertilizer in combination with cover cropping and reduced tillage. However, this positive N balance was mainly due to a reduction in N removal with harvest and NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {NO}_3^{-}$$\end{document} leaching. The use of highly decomposable organic matter and cover cropping did not lead to any N yield penalty while decreasing NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {NO}_3^{-}$$\end{document} leaching. These results highlight that organic practices combined with reduced tillage and cover cropping can optimize the use and recovery of N resources.