Characteristics of Raindrop Throughfall Under Corn Canopy

ABSTRACT A laboratory rainfall simulator was used to study the raindrop size and velocity under a corn canopy. Drop sizes were measured by using a dye-paper technique, and drop velocities were measured photographically. Stemflow was calculated on the basis of rainfall under the canopy and incident rainfall above the canopy. Up to 49% of incident rainfall appeared as stemflow. Drops that directly penetrated the crop canopy accounted for much of the throughfall kinetic energy; drips from leaf margins also contributed greatly to throughfall kinetic energy. Drops that splashed from leaves were quite small and contained little kinetic energy. The ratio of the kinetic energy at ground level to kinetic energy at the top of the canopy was compared with the ratio predicted by Wischmeier and Smith (1978) for use in the Universal Soil Loss Equation. The comparison indicated little difference between what we observed and that predicted.