This is an excellent presentation by Jay Fuhrer, who works for the Natural Resource Conservation Service in North Dakota, USA. He uses case studies to explain how innovative use of cover crops can boost soil health and productivity, and dramatically reduce the use of artificial fertilizers.
Watch the global carbon cycle! The link below takes you to a NASA page that loads a 90 megabyte animated GIF file showing chlorophyll concentration (in the oceans) and Normalized Difference Vegetation Index (NDVI, on land) as the seasons change. Note: this page requires a fair bit of computer memory and good internet connection to load the image. It may step around slowly until the image is fully loaded.