Influence of long-term phosphorus fertilisation history on the availability and chemical nature of soil phosphorus
Date
2019
Authors
van der Bom, F.J.T.
McLaren, T.I.
Doolette, A.L.
Magid, J.
Frossard, E.
Oberson, A.
Jensen, L.S.
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Journal article
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Geoderma, 2019; 355:113909-1-113909-12
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F.J.T. van der Bom, T.I. McLaren, A.L. Doolette, J. Magid, E. Frossard, A. Oberson, L.S. Jensen
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Abstract
Data on the dynamics and fate of phosphorus (P) under low soil-test P (STP) conditions is essential for the development of cropping strategies with a high P use efficiency. This study examined the effects of long-term (20 years) mineral and organic fertiliser P applications on a P-depleted sandy loam soil in Denmark. The cycling of P was examined by use of P budgets (inputs-offtake), chemical P extractions, ³³P isotopic exchange kinetics (IEK), and solution ³¹P nuclear magnetic resonance (NMR) spectroscopy on NaOH-EDTA extracts. Recovery of applied P in the topsoil was smaller for animal slurry P compared with mineral fertiliser P. The budgets suggest deeper soil layers play an important role for the cycling of P. Resin-extractable P (2 to 17 mg kg⁻¹), Olsen-P (7 to 16 mg kg⁻¹) and E1min (1 to 6 mg kg⁻¹) were correlated with the P budgets. Between 63 and 77% of total inorganic P was not exchangeable in a period of three months (E>3months), with the lowest value observed in no-P treatment N₁K₁. The data show that a redistribution of exchangeable P had taken place under the influence of a strongly negative P budget. Microbial P (6 to 18 mg kg⁻¹) increased under animal slurry inputs compared with mineral fertiliser applications (p < 0.05). All soils were dominated by phosphomonoesters and orthophosphate (98 to 99% of the NMR signal). Concentrations of orthophosphate (86 to 135 mg kg⁻¹) varied significantly between treatments (p < 0.01), whereas forms of organic P remained largely unchanged. The results demonstrate that P applications increased the amount of P that is potentially available for plants, irrespective of input form. Nevertheless, most P applied in excess of crop uptake resulted in an increase of the amount of P that is slowly exchangeable. Under low soil test P conditions such as in the current trial, fertiliser P applied in excess of plant demand that accumulates in soil would thus only be partially available for crops in subsequent years. On the other hand the data suggests that soil P reserves may be utilised for crop growth, but at the low soil P intensity plant access to P will have to be managed carefully.
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© 2019 Elsevier B.V. All rights reserved.