The adjective campestral is an uncommon way to describe something connected to the wide open countryside. You could describe a field full of wildflowers as campestral.
When you need an impressive or scholarly way to describe a rural scene, use the word campestral. Acres of prairie grasses are campestral, and so are rolling green hills and bucolic country fields. Campestral is rooted in the Latin word campester, which means "of a field," and which in turn comes from campus, or "field."