Fluorine Concentrations in Greenhouse Soils Sampled from Farms in Southern Kyushu, Japan

Phosphate fertilizer is thought to be the major source of F input in agricultural soils. We consider that F accumulation in Japanese agricultural soil is caused by excessive application of phosphate fertilizer, because Japan is one of the major chemical fertilizer consumer nations in the world. In this study, we analyzed the F concentration in greenhouse soils sampled from farms in southern Kyushu, Japan, and investigated the possibility of the F accumulation in the soils by comparing the concentrations in the greenhouse soils with those in neighboring non-cultivated soils. The total F concentration in non-cultivated soils and greenhouse soils ranged from 53 to 248 mg/kg and from 163 to 471 mg/kg, respectively. Almost all greenhouse soils had a higher total F concentration than the neighboring non-cultivated soils, which indicates that total F concentrations were generally higher in almost all greenhouse soils. The water-soluble F concentrations in non-cultivated soils and greenhouse soils ranged from 0.15 to 4.89 mg/kg and from 1.75 to 20.3 mg/kg, respectively. As well as total F concentration, almost all greenhouse soils had a higher water-soluble F concentration than the neighboring non-cultivated soils. A positive correlation was observed between the total F and the total P concentrations in greenhouse soils, which indicates that the F in the greenhouse soils is derived from phosphate fertilizers. The above results indicate that soil F accumulation is due to excessive application of phosphate fertilizers that are widely used on greenhouse soils throughout Japan, and water-soluble F concentrations are correspondingly elevated in these soils.