Abstract: Disclosed is a liquid mulching agent composition, which is environmentally friendly due to use of seaweed, facilitates soil coating, and has high light blocking efficiency, making it possible to control heat retention and water content in the soil. The liquid mulching agent composition includes a seaweed extract, a first component including at least one selected from the group consisting of humic acid, fulvic acid, and charcoal, and a second component including at least one selected from the group consisting of sodium alginate, polyvinyl alcohol, keratin, and sodium silicate.