Qs about old exams

1. Under what circumstances can phosphate leaching become a problem? 1st review the P cycle. Consider why P leaching is seldom a problem (i.e. what happens to PO4 in soils)? Hint consider why available PO4 in soil solution is low. 2nd under what circumstances can phosphate leaching be an issue? Hints: consider inputs and pH.

2. Nematodes (threadworms) are micro-fauna (<0.2 mm). There are 2 major "types" of nematodes - what are they? To answer your question, consider their food sources and their role(s) in soils.

3. Ahb horizon. 1st give definitions for h and b (and consider the processes their associated processes). 2nd think about the environmental conditions which may commonly lead to the formation of an Ahb horizon. Note that erosion implies the removal of soil (not deposition) but you are on the right track.

4. Sources of P and S. Review the P and S cycles AND slide 16 of lecture 25 (soil as a source of plant nutrients). Sulfide minerals, phosphate minerals and SOM are important sources.