Relation between soil P test values and mobilization of dissolved and particulate P from the plough layer of typical Danish soils from a long‐term field experiment with applied P fertilizers |
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Authors: | C Kjaergaard G H Rubæk J Magid |
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Institution: | 1. Department of Agroecology, Aarhus University, , DK‐8830 Tjele, Denmark;2. Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, , DK‐1871 Frederiksberg C, Denmark |
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Abstract: | Accumulation of phosphorus (P) in agricultural topsoils can contribute to leaching of P which may cause eutrophication of surface waters. An understanding of P mobilization processes in the plough layer is needed to improve agricultural management strategies. We compare leaching of total dissolved and particulate P through the plough layer of a typical Danish sandy loam soil subjected to three different P fertilizer regimes in a long‐term field experiment established in 1975. The leaching experiment used intact soil columns (20 cm diameter, 20 cm high) during unsaturated conditions. The three soils had small to moderate labile P contents, expressed by water‐extractable P (3.6–10.7 mg/kg), Olsen P (11–28 mg/kg) and degree of P saturation (DPS) (25–34%). Mobilization of total dissolved P (TDP) increased significantly (P < 0.05) from the intact soil columns with increasing labile P, whereas the increase in particulate P (PP) with increasing labile P content was modest and statistically insignificant. We found concentrations up to 1.5 mg TP/L for the plough layer of this typical Danish sandy loam soil. This highlights that even a moderate labile P content can be a potential source of TDP from the plough layer, and that a lower concentration margin of optimum agronomic P levels should be considered. |
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Keywords: | Dissolved phosphorus particulate phosphorus leaching mobilization labile phosphorus soil phosphorus status Olsen phosphorus water‐extractable phosphorus oxalate‐extractable phosphorus iron and aluminium |
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