N Cycle Animated
N Cycle, Dr. Robert Mullen
N Cycle (dial)
NASA, Global Warming (current CO2 level)
We do not have a "companion earth" to test this against.
We have to get it right the first time.
Bumper Sticker, Nitrogen Cycle and Global
Nitrogen Cycle Poem (2014)
Raun et al. (1997).
Nitrogen cycle ninja, a teaching
exercise. J. Nat. Resour. Life Sci. Educ.
Carbon-Nitrogen Cycles, SOIL 5813 Class
2015, USA (source USDA ISSN 1949-1522)
World Nitrogen Use Efficiency for Cereal Production is 33%,
Agronomy Journal 91:357
NITROGEN Publications from Oklahoma State University