Phosphorus Forms Determined By 31P-NMR in Grassland Soil.

Different techniques can be used to determine the forms of soil phosphorus (P), but the preferred technique is ³¹P nuclear magnetic resonance (NMR) spectroscopy. This study was conducted to assess the effects of P fertilization on P forms as determined by ³¹P-NMR. The experimental site is located at the Harlaka Experimental Farm of Agriculture and Agri-Food Canada near Québec City, Canada. The soil is a Kamouraska clay. Four P rates (0, 10, 20, and 40 kg P ha^-1) replicated four times have been applied each year since 2010 to a previously established timothy sward. Only three replications and three P rates (10, 20, and 40 kg P ha^-1) were considered in this study for a total of nine plots.  Soil samples (0-10 cm) were collected in fall 2013 and were analysed for different parameters including P as extracted by Mehlich 3  (PM3, the recommended method) and with solution ³¹P-NMR. Results indicated that PM3 was greater with P fertilization (29.36 mg kg^-1) that without (12.33 mg kg^-1). Other results will be presented and discussed.