Effects of land use change on P bioavailability determined by chemical fractionation and 31P-NMR spectroscopy in a Nothofagus forest and adjacent grassland

• Published in: Journal of soil science and plant nutrition 2015-12, Vol.15 (ahead), p.1061-1070
• Main Authors: Redel, Y. D, Escudey, M, Alvear, M, Conrad, J, Borie, F
• Format: Article
• Language: English
• Subjects: SOIL SCIENCE
• ISSN: 0718-9516; 0718-9516
• DOI: 10.4067/S0718-95162015005000074

The aim of this study was to compare P bioavailability in a Nothofagus rainforest Andisol (FS) and an adjacent clear-cut grassland soil (GS) in southern Chile to evaluate the effects of land use change on P chemical forms determined by chemical fractionation and 31P-NMR spectroscopy. Total phosphorus (P), Olsen P, microbial P, different soil P fractions (determined using a modified Hedley procedure), 31P-NMR spectroscopy results, acid phosphatase (P-ase) activity, pH and organic C were analyzed and compared. Forest samples were collected from the mineral soil at a depth of 2-20 cm and were compared with those collected from grassland soil at the same depth. Total P ranged from 2028 mg kg-1 (FS) to 2157 mg kg-1 (GL)and total organic P ranged from 829 mg kg-1 (FS) to 1176 mg kg-1 (GL). On the contrary, Olsen P, microbial P, labile P and P-ase activity were higher in the evergreen forest soil than in the grassland, with the predominance of the moderately labile (NaOH-Po) fraction, which ranged from 668 to 720 mg kg-1 in both soils. Phosphorus was mainly present in monoester-P form in the NMR extract in both soils (67 % on average). Other 31P-NMR signals were identified as C2-myo-inositol phosphate and scyllo-inositol hexakisphosphate. The results suggest that land use change from forest to grassland will reduce P bioavailability and P-ase activity.