Andisols are characterized by a high phosphorus (P) fixation capacity, which is a limiting factor for plant production.Continuous application of P fertilizer may result in an accumulation of P associated with soil organic matter (SOM), which further acts to reduce the availability of the added P. The objectives of this study were (1) to evaluate the impact of P fertilizer inputs on the quantities and chemical forms of P, and (2) to investigate relationships between P forms SOM and land use.Topsoil (0-20 cm) and subsoil (20-40 cm) samples were taken from two Andisols series under grassland and arable cropping.Soil P forms were determined using sequential fractionation, while SOM analysis involved a combination of 13 C nuclear magnetic resonance (NMR) spectroscopy and pyrolysis-GC-mass spectrometry.Fertilization increased total P, total organic P, organic carbon, and inorganic P fractions, mainly in arable soils.Labile P was higher in grassland (3% of total P) than in arable soils (1% of total P).A clear effect of fertilization was observed on organic matter compounds measured by pyrolysis in both soil depths.Interestingly, the polysaccharide-derived compounds increased in fertilized soils and lipidderived compounds decreased.Thus fertilization principally affected labile P and labile SOM forms, whereas recalcitrant forms of P and SOM remained unchanged.
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Velásquez et al. (2016) studied this question.