Encyclopedia of Earth
Encyclopedia of Earth: Biogeochemistry: Phosphorus Cycle
Article explaining what the phosphorus cycle is, where it occurs, its place in the biotic world, and the environmental impact of human activities on the phosphorus cycle. (Published: October 8, 2009)
Other
Ed Hume Seeds: Testing Your Soil
Conduct a soil test to find out what nutrients your soil is lacking. This site gives directions on how to gather a soil sample and what nutrients you should test for to get the best soil.