Reduction in tillage and especially no-till practices have been correlated with reductions in runoff and increased water infiltration. The mechanisms allowing increased infiltration rates have not been specifically identified. We conducted a series of investigations to determine the relative roles of carbon stratification, aggregate stability, macropores, and depth of tillage on ponded infiltration rates. Dye tracing techniques clearly indicated that, while the rate of water flow is highly heterogeneous through the soil matrix, flow through earthworm-size macropores did not make a significant contribution to infiltration. Water-stable aggregation did correlate to ponded infiltration rates and to surface runoff rates under field conditions. Soil under wheat stubble always had greater infiltration capacity than the preceding young crop. Surface residue, independent of tillage, did improve ponded infiltration. Our conclusions are that organic carbon concentration near the soil surface plays a major role in reducing surface sealing, and minimizing soil disturbance at deeper depths allows preservation of high velocity flow paths. This might explain why very weakly aggregated soils under low residue production sometimes demonstrate little improvement under no-till.