1. What are the five processes in the nitrogen cycle?
2. What are the two principle forms of nitrogen used by plants?
3. What environmental problems are associated with excess nitrogen?
4. What are the primary natural sources of sulfur?
5. List three major sources of gains and three losses of available sulfur in soils.
6. Why is phosphorus often limited in soils?
7. What environmental problems are associated with phosphorus?
8. What are the benefits of potassium to plants?
9. What problems are associated with potassium in soils?
10. List the pools of calcium within soils.