Inhomogeneity effect on full energy peak (FEP) efficiency in a soil sample was determined using the Monte Carlo simulation technique. The dependence of the FEP efficiency on the homogeneity in the soil was obtained for some particular photon energies ranging from 60 keV to 2 MeV and, as a result, the corresponding correction factors were obtained. This effect was more significant at lower energies and for higher inhomogeneity rates.