ooc: Good point, but there is still damage that may affect his movement. here is the RAW:
[sblock=RAW](D) Dismissible
If the Duration line ends with "(D)," you can dismiss the spell at will. You must be within range of the spell’s effect and must speak words of dismissal, which are usually a modified form of the spell’s verbal component. If the spell has no verbal component, you can dismiss the effect with a gesture. Dismissing a spell is a standard action that does not provoke attacks of opportunity.
here is the blarb I am concerned about:
duration does not have the "(D)" and . . . .
A successful attack by a caltrop deals 1 point of damage. If the target is Small, Medium, or Large, its land speed is reduced by one-half because of the injury. This movement penalty lasts for 24 hours, until the creature is successfully treated with a DC 15 Heal check, or until it receives at least 1 point of magical healing[/sblock]