A spectroscopy system measuring inelastic neutron scattering and thermal neutron capture induced gamma-rays is being developed for in-situ soil analysis. Because a pulsed fast D-T neutron source is utilized, fast neutron induced inelastic neutron scattering reactions are separated in time from thermal neutron capture events. Models utilizing the MCNPX code have been developed to study the time and energy variations of the neutrons in the soil matrix.