But I'm always looking for more resources to help students understand the relevance of Nitrogen and its cycle. I recently discovered a wonderful episode on Hulu Plus (requires a subscription) which is perfect. It is from a BBC Earth show called The Great Rift: Africa's Wild Heart.
The episode (Season 1, Episode 3) is simply called Grass.
Throughout this episode the narrator draws a lot of attention to Nitrogen. He explains the importance of Nitrogen to the living things of the area, and it made the relevance of this element crystal-clear, without being too pedantic. Highly recommended when studying Chemistry, Ecology, or Agriculture!
P.S. I just finished watching Episode 2 Water and it's actually about Plate Tectonics. Wonderful for Geology or World Geography: Africa!!!