To provide a novel technology capable of increasing yield in direct seeding cultivation.SOLUTION: A yield increasing agent included in a coating composition used for coating plant seeds, includes a porous substance, and one or two or more kinds of yeast decomposition products selected from a group comprising a yeast extract, a yeast cell wall and a decomposition product of the yeast cell wall which are adsorbed onto the porous substance. In the yield increasing agent, the yeast decomposition product is included as much as 1-15 wt% per yield increasing agent.SELECTED DRAWING: None【課題】直播栽培において収量を増加させることができる新規な技術を提供する。【解決手段】 植物種子の被覆のために用いられるコーティング用組成物に含有される収量増加剤であって、多孔質物と、多孔質物に吸着されている、酵母エキス、酵母細胞壁及び酵母細胞壁の分解物からなる群から１種または２種以上選択される酵母分解物と、を含み、酵母分解物が収量増加剤当たり１～１５重量％含有される収量増加剤。【選択図】 なし
