Let X be a Banach space and ${psi}$ a continuous convex function on ${Delta}_{K+1}$ satisfying certain conditions. Let $(X{igoplus}X{igoplus}{cdots}{igoplus}X)_{psi}$ be the ${psi}$-direct sum of X. In this paper, we characterize the K strict convexity, K uniform convexity and uniform non-$l^N_1$-ness of Banach spaces using ${psi}$-direct sums.