The transport of a solute in a soil column is considered for zero-order kinetics. The visible displacement of the solute is affected by dispersion. The dispersion coefficient enters both the transport equation and the boundary condition. It is shown that the latter is the most important effect and a simple equation is proposed to describe solute transport, which takes into account the influence of dispersion in the boundary condition, but not in the transport equation. Validity and limitations of this equation are discussed in some detail by comparison with the complex but exact solution for zero-order kinetics.