Total and soluble fluorine concentrations in relation to properties of soils in New Zealand

Abstract

Summary Soil fluorine (F) concentrations continue to increase in agricultural soils receiving regular applications of phosphatic fertilizer. Continued accumulation of soil F poses a risk to grazing ruminants and may pose a future risk to groundwater quality. This paper examines the range of total F (Ft) concentrations and forms of soluble F species and their relationship to selected soil properties in New Zealand agricultural soils. The Ft and soluble F (soil F extracted with water (Fwater) and 0.01 m KCl (FKCl)) concentrations in 27 soil samples (0–75 mm depth) taken from predominantly pasture sites in the North and South Islands of New Zealand were much less than those reported in the literature for sites contaminated with F from industry. The Ft concentrations ranged from 212 to 617 µg F g−1 soil. The F‐toxicity risk to grazing animals in farms at these sites through soil ingestion is small at present, but farms with very large Ft concentrations (i.e. > 500 µg F g−1) need to adopt suitable grazing and fertilizer management practices to avoid future F‐toxicity risk. The Ft concentration had very strong positive correlations with both total soil P and total soil Cd concentrations, reflecting the link between P fertilizer use and F accumulation in the soils. It also had significant positive correlations with organic matter and amorphous Al oxides contents, indicating that F is strongly bound to Al polymers adsorbed to organic matter and amorphous Al oxides. The Fwater and FKCl concentrations and free F– ion concentrations in water (F–water) and 0.01 m KCl (F–KCl) extracts were generally two and three orders of magnitude, respectively, less than the Ft concentrations and were much less than the concentrations considered phytotoxic. The Fwater and FKCl concentrations were positively related to soil organic matter content and negatively related to soil pH. Regression models relating Fwater and FKCl concentrations to soil organic matter content and soil pH suggest that F can be very soluble in extremely acidic soils (pH(water) < 4.9) with large organic matter contents and therefore F potentially may contaminate groundwater if these soils are also coarse‐textured and the water table is shallow.

Soil Properties and Trace Elements Contents Following 40 Years of Phosphate Fertilization

“…A significant increase in total F was not found where the values were near or within the world's average (Helmke, 2000, Gladney and Burns, 1985; Chen et al, 1991). On the other hand, the amount of water‐soluble F showed a consistent and significant increase in the 0‐ to 30‐cm interval with increasing P application, which is presumably influenced by the decrease of soil pH ( r = −0.92, p < 0.01) (Table 6) (Pickering, 1985; Barrow and Ellis, 1986; Loganathan et al, 2006).…”

Pasture Soils Contaminated with Fertilizer-Derived Cadmium and Fluorine: Livestock Effects

“…Adriano (2001) reported that in soils where the Cd is present at background level the residual Cd fraction is usually dominant, whereas in most highly contaminated soils this fraction may not account for a large proportion of the total soil Cd. On the other hand, soil aging may also lead to increases in Cd The quantity of Cd and F in soil solution represents <1% of their total soil contents (Gray et al 1999b;Loganathan et al 2006;Taylor and Percival 2001). In soil solution, Cd and F occur both as free ionic forms and complexed with other ions (see Fig.…”

Phosphorus: Chemism and Interactions

“…But it should be noted that P affects the availability of F only in case of very high amounts of P in soil. Therefore, in our experiments a statistically significant increase of soluble F was detected in the both soil depths in accordance with the rates of the applied fertilizer, which presumably were induced by the decrease of soil pH (r=-0.92 p < 0.01) (Pickering, 1985;Barrow & Ellis, 1986;Loganathan et al, 2006). The significant increase of the amount of soluble F in the subsurface soil might be due to its leaching from the upper soil layer.…”

“…They can maintain or improve crop yields, but they can also cause changes in the chemical and physical properties of the soil, both directly and indirectly (Hera & Mihaila, 1981;Acton & Gregorich, 1995;Aref & Wander, 1998;Belay et al, 2002). By affecting the basic soil properties (pH, organic C and N, cations, CEC, granulometic composition), phosphate fertilization may influence the solubility of certain elements, such as Al, F, Ca, and Mg (Lindsay, 1979;Kabata-Pendias & Pendias, 2001;Loganathan et al, 2006). On the other hand, mineral phosphate fertilizer could provide an abundance of available phosphorus in soil and increase the efficiency of metal-phosphate mineral formation (Ma et al, 1993;Berti & Cunningham, 1997;Hettiarachhchi et al, 1997;Cooper et al, 1998).…”