除塩された水田土壌の製鋼スラグ系肥料の施用による改善(津波被災水田の製鋼スラグ系肥料による復興−1)

抄録

Paddy fields located near the coast of northeastern Japan have suffered significant damage from the tsunami caused by the earthquake. The restoration of a damaged paddy field can be achieved with the washing out of Na by desalting treatment and fertilization with silica. The concentration of Na can be effectively reduced with Ca supplements. As steelmaking slag contains CaO and SiO₂, it has a strong potential to become an economic solution for the recovery of fields.
To evaluate the effect of fertilizer made of steelmaking slag, a new soil-filled column testing method was developed to simulate the paddy field conditions. The column was composed of a plow layer containing pore water and soil with fertilizer, along with a layer of surface water. Every day, water sample was collected from the bottom of the column and the same amount of fresh water was supplied for approximately 2 months. The original soil and the soil after desalting were used with and without fertilizer made of steelmaking slag. The influence of soil particle size was also investigated.
During the experiment, the pH increased, while the oxidation and reduction potential decreased day by day; thus, the typical changes under paddy field conditions were simulated. Supplementation with fertilizer made of steelmaking slag led to the increase in Ca content and pH. In contrast, most of the Na was washed out by water exchange during the experiment; however, an initial decrease in its content was observed by the addition of fertilizer made of steelmaking slag.