PROBLEM TO BE SOLVED: To provide a plant growth base material helpful to effective use of sludge. SOLUTION: This plant growth base material comprises a mixture of dry sludge and soil or wood chips in the volume ratio of 1:1 or a mixture of dry sludge and soil, and wood chips in the volume ratio of 1:1. Alternatively, the other version of this base material comprises a mixture composed of the above- mentioned components in the above volume ratios and added with a soil- aggregate agent.