We explore the deconvolution of waternitrate correlations by the first-order difference approach involving neutron diffraction of heavy- and null-aqueous solutions of KNO3 under N-14/N-15 and O-nat(N)/O-18(N) substitutions to achieve a full characterization of the first water coordination around the nitrate ion. For that purpose we performed isobaricisothermal simulations of 3.5 m KNO3 aqueous solutions at ambient conditions to generate the relevant radial distribution functions required in the analysis (a) to identify the individual partial contributions to the total neutron-weighted distribution function, (b) to isolate and assess the contribution of NO3-.....K+ pair formation, (c) to test the accuracy of the neutron diffraction with isotope substitution based coordination calculations and X-ray diffraction based assumptions, and (d) to describe the water coordination around both the nitrogen and oxygen sites of the nitrate ion.