1) Add this as the first line of your script:
#!/bin/sh
Your terminal might understand how to interpret your script, but crond can't, so the system will have to depend on this line to know how to execute it.
2) I recently learned a good lesson (
) on paths. System applications will probably always work, but in other cases it might be a fine idea to specify the entire path which you'd get when using "whereis application".