I will present an effective version of a result due to Einsiedler, Mozes, Shah and Shapira who established the equidistribution of primitive rational points on expanding horospheres in the space of unimodular lattices in at least 3 dimensions. Their proof exploits measure classification results. We pursue an alternative approach, based on Fourier analysis, additive twists of automorphic forms, spectral theory and Weil’s bound for Kloosterman sums in order to quantify the rate of equidistributionfor a specific horospherical subgroup.