The use of dry grass mulch in cotton furrows substantially increased irrigation efficiency in recent tests at the U. S. Cotton Field Station, Shafter. The millet and sudangrass used in these tests was seeded in 8-inch bands down the furrows and then desiccated by oil-spraying when growth reached 10 to 18 inches high. Time required for irrigation water to flow down the furrows was nearly doubled by the sudangrass mulch. Infiltration rates were substantially increased by the grass mulches and a greater soil water content, following irrigation, was obtained. While cotton seed yields showed no significant differences in these tests, data indicated that both crop uniformity and yield improvements could result from use of grass mulches on soils with low infiltration rates.