Bio-char can be obtained from plant biomass through energy-yielding processes, and is a promising soil amendment that could benefit crop production and carbon sequestration. We report on data obtained from ongoing bio-char amendment studies at a field site on a Colombian Oriental savanna Oxisol. While single bio-char applications 8 and 20 Mg ha-1 did not have a significant effect on maize yield in the first year, maize yields increased on average by 15 and 23 %, respectively, in both the second and third year relative to the control. All plots including those not receiving bio-char were fertilized with NPK. Apart from reported improvements in soil fertility, bio-char may have lead to an increase in crop growth through an alteration of water relations, as measured by field-installed tensiometers and zero-tension lysimeters. In plots that had received a 20 Mg ha-1 bio-char addition in 2002 and that were cropped to maize in 2005, rain infiltration was slower when compared to the unamended control at all monitored depths of 15, 30, 60, 120 and 200 cm. Such infiltration and percolation patterns may have implications for nutrient leaching and the export of nutrients from the root zone of crops. This presentation will focus on hydrological and leaching data collected from this Colombian savanna experiment.