The grey mare (S) rode across (V) the field (Object D) with great care (Adv).

The grey mare (S) rode (V) across the field (Object prep) with great care (Adv).

Is the rode across (predicate) and the field (object direct) or should rode be alone as a predicate and across the field (object prepositional) ???

I'm confused when the preposition goes with the verb and when with the object. If a verb is a phrasal does it always have to be followed by an object direct????