PROBLEM TO BE SOLVED: To overcome a problem that organic acid components such as acetic acid are known to be generated by an explosive-shattering treatment of wood chips, the organic component reduce pH of a ligneous crude fiber, inhabitation of microorganisms becomes difficult by effects of acidity when the wood chips are used as a soil improving material and soil improving performance is reduced.SOLUTION: There is provided a soil improving material containing fulvic acid or humic acid and a ligneous crude fiber.SELECTED DRAWING: Figure 1