On a complete Riemannian manifold (M, g), we consider \(L^{p}_{loc}\) distributional solutions of the differential inequality \(-\Delta u + \lambda u \ge 0\) with \(\lambda >0\) a locally bounded function that may decay to 0 at infinity. Under suitable growth conditions on the \(L^{p}\) norm of u over geodesic balls, we obtain that any such solution must be nonnegative. This is a kind of generalized \(L^{p}\) -preservation property that can be read as a Liouville-type property for nonnegative subsolutiuons of the equation \(\Delta u \ge \lambda u\) . An application of the analytic results to \(L^{p}\) growth estimates of the extrinsic distance of complete minimal submanifolds is also given.