Summary: We obtain a characterization of totally geodesic horizontally conformal maps by a method which arises as a consequence of the Bochner technique for harmonic morphisms. As a geometric consequence we show that the existence of a non-constant harmonic morphism \(\phi\) from a compact Riemannian manifold \(M^m\) of nonnegative Ricci curvature to a compact Riemannian manifold of non-positive scalar curvature, forces \(M^m\) either to be a global Riemannian product of integral manifolds of vertical and horizontal distributions or to be covered by a global Riemannian product.