PROBLEM TO BE SOLVED: To provide an application method for a water area environment conservation material capable of effectively and continuously supplying iron ions to a water area.SOLUTION: The application method for the water area environment conservation material includes: a humic acid supply substance fermentation step for generating a humic acid by fermenting a humic acid supply substance； a water area environment conservation material manufacturing step for manufacturing the water area environment conservation material by mixing the humic acid supply substance containing the humic acid prior to the fermentation step with an iron containing substance； and an application step for applying the water area environment conservation material to the water area. A secular change in the content of the humic acid is measured in the humic acid supply substance fermentation step and while utilizing a relation between a fermentation period and the content, the humic acid supply substance before the content of the humic acid reaches a maximum content is mixed with the iron containing substance in the manufacturing step.SELECTED DRAWING: Figure 1【課題】鉄イオンを効果的、且つ、持続的に水域に供給することを可能とする水域環境保全材料の施用方法を提供する。【解決手段】腐植酸供給物質を発酵させて腐植酸を生成させる腐植酸供給物質の発酵工程と、前記発酵工程後の前記腐植酸を含む前記腐植酸供給物質を、鉄含有物質と混合して水域環境保全材料を製造する水域環境保全材料の製造工程と、前記水域環境保全材料を水域に施用する施用工程とを備える、水域環境保全材料の施用方法であって、前記腐植酸供給物質の発酵工程にて、前記腐植酸の含有量の経時変化を測定し、発酵期間と前記含有量との関係を利用して、前記腐植酸の含有量が最大量に到達する以前の腐植酸供給物質を、前記製造工程にて、前記鉄含有物質と混合する。【選択図】図１
