Journal Article N762921K75 Nitrogen Soil 7664-41-7 Ammonia nitrification nitrogen addition 142M471B3J 7440-44-0 Carbon Carbon Dioxide Grain Proteins K50XQU1029 Meta-Analysis Nitrous Oxide Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. ammonia oxidizers biological and chemical processes carbon cycle-climate feedbacks carbon losses climate change climate change adaptation climate change impact denitrification field in situ observation food security global change factors grain protein