Baugé, S. M. Y., Lavkulich, L. M. and Schreier, H. E. 2013. Serpentine affected soils and the formation of magnesium phosphates (struvite). Can. J. Soil Sci. 93: 161–172. The Sumas River watershed, located in the intensive agricultural region of the Lower Fraser Valley of British Columbia (Canada), contains serpentine asbestos from a natural landslide. Serpentinic soils have a high Mg to Ca ratio that can affect soil fertility, including soil-solution P relations. The objectives of the study were: (i) to evaluate some common methods of estimating plant available phosphorus in the surface horizons of the serpentine-affected soils and those receiving large quantities of livestock manure, and (ii) to determine if there is evidence for the formation of soluble Mg phosphates, e.g., struvite, a meta-stable P phase in these soils. Seven soil nutrient extractants were used to determine major and minor elemental concentrations. Acid ammonium oxalate, 1 M HCl and Bray P1 extractions were most effective for measuring available phosphorus in these soils. Manure and fertilizer applications appear to favor the formation of Mg-phosphates, and are considered to be more soluble in terms of phosphorus than either calcium-phosphates or aluminum/iron-phosphates. X-ray diffraction, scanning electron microscopy and nuclear magnetic resonance examinations gave positive evidence for the presence of struvite in the soils.

Baugé, S. M. Y., Lavkulich, L. M. and Schreier, H. E. 2013. Phosphorus and trace metals in serpentine-affected soils of the Sumas Basin, British Columbia. Can. J. Soil Sci. 93: 359–367. Soils of the Sumas watershed in the Lower Fraser Valley of British Columbia have contrasting P, Mg and trace elements contents arising from two major sources, periodic deposition of serpentine-rich sediments and intensive agricultural activities. Four study sites were examined for soil P by several extractants commonly used for P availability assessments. The results were compared with aqua regia to determine best estimates of extractable P. In addition, these extractants were evaluated as indices of associated trace metal amounts. Aqua regia, acid ammonium oxalate and 1 M HCl extracted similar amounts of P and trace metals. Acid ammonium oxalate was found to be closely related to the estimates of total P and recoverable elements, followed by 1 M HCl. There was clear separation of the sites by both P values and trace elements associated with serpentine (Cr and Ni) and those from agricultural activities (Cu and Zn). Results suggest that a single extraction, 1 M HCl, can be an effective measure of both available P and trace elements in serpentinitic soils.

Baugé, S. M. Y., Lavkulich, L. M., Wilson, J. E. and Schreier, H. E. 2014. Comparison of surface properties of synthetic and soil struvite. Can. J. Soil Sci. 94: 169–176. X-ray, Raman and nuclear magnetic resonance (NMR) analyses of intensively managed agricultural soils in southwestern British Columbia reported the presence of the Mg-phosphate mineral, struvite. Soils are heterogeneous, thus analytical techniques based on single minerals require calibration in order to provide reliable results. A synthetic struvite was used to compare the properties of the soil phosphate with struvite. The results confirmed the presence of struvite and possibly additional species of Mg. Time of flight–secondary ion mass spectroscopy (TOF-SIMS) revealed that the surface of struvite, to 2nm depth, is dominated by Mg with other cations, notably Fe and NH4 that were measured in minor amounts and were associated with the Mg rich surface layer. The results suggest that P is located within the struvite structure. Chemical reactions of struvite and phosphorus chemistry in these soils appear to be governed by the Mg surface layer.