Application of fertilizer made of steelmaking slag in the recovery of paddy fields damaged by the Tsunami of 2011

The great earthquake of 2011 triggered a tsunami that damaged large areas of paddy fields in northeastern Japan. In an effort to address the salt damage, supplementation of Ca-containing materials to exchange Na adsorbed on soil surface has been recommended. In addition, Si has also been shown to enhance paddy growth. Steelmaking slag, which contains a water-soluble solid solution phase of 2CaO•SiO₂, can supply Ca and Si for soil remediation. In this study, the dissolution behaviors of nutrient elements from fertilizer made of steelmaking slag were investigated using the column test. In addition, crop cultivation experiments were also conducted using tsunami-damaged paddy fields. In column test, Ca content in soil solution increased by the application of fertilizer made of slag, but the Na content did not change significantly. These trends were also observed in the pore water of the actual paddy in crop cultivation experiments. In addition, the incremental trend of silicate content in the pore water by the application of fertilizer made of slag was more apparent than that in the column test. Paddy growth was enhanced and the yield of brown rice was increased by the application of fertilizer made of slag. In conclusion, the fertilizer made of steelmaking slag has the following three effects: (1) mitigating the damage caused by the Na ion through the supplementation of Ca, (2) enhancing the mineralization of soil N by increasing the pH, and (3) accelerating photosynthesis by the supplementation of silicate.