1. Would you consider the weed species you selected to be an effective competitor? In what situations will your species be competitive and not be competitive?

2. What is competition, and why is it so difficult to define?

3. What type of competition would you expect to find in an agricultural field? How would this be altered by changing light patterns within the crop canopy or by the addition of fertilizer? Why?

4. Briefly explain Grime's and Tilman's views of competition. In what ways are they similar? In what ways do they differ?

5. Is allelopathy likely to be more important in agricultural or natural systems? Explain why.

6. Compare Baker's (1956, 1974) list of weed traits (Box 1.1) with Zimdahl's (1999) list of competitive weeds (Table 8.2). Explain their similarities and differences.

7. Design an allelopathy experiment.

8. Why is it so difficult to determine how competition and allelopathy occur (i.e. define the mechanism)?

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