Phosphorus Availability for Plant Uptake in a Phosphorus‐Enriched Noncalcareous Sandy Soil

Abstract

Mining soil phosphorus (i.e., harvesting P taken up from the soil by a crop grown without external P addition) has been proposed as a possible management strategy for P-enriched soils to decrease the risk of P leaching. We performed a pot experiment in a greenhouse where grass was cropped on a P-enriched noncalcareous sandy soil at zero P application over a period of 978 d. We determined the long-term availability of soil P and evaluated the effectiveness of mining soil P to decrease P in different pools. There were two treatments: soil layers in the pots of either 5 or 10 cm thickness. Soils were analyzed at various stages of the experiment. Phosphorus in soil solution and the total pool of sorbed P were estimated using 1:10 (w/v) 0.01 M CaCl2 extracts and acid ammonium oxalate (P(ox)), respectively. A desorption isotherm was constructed, which described the relationship between P in soil solution and the total pool of sorbed P for the soils of the 5- and 10-cm treatments. The Langmuir equation gave a very good description of the isotherm. In the long-term, 65% of P(ox) in the initial soil can be removed by plant uptake, as was calculated from the Langmuir equation and a critical P concentration in soil solution at which P uptake can just be maintained. Thus, P(ox) may be largely plant available. From the strong nonlinearity of the desorption isotherm, it can be understood why the relative decrease of the P concentration in the CaCl2 extracts was much larger than the relative decrease of P(ox). Mining soil P decreased the P concentration in soil solution effectively and, therefore, risk of P leaching from our P-enriched soil.

A quantitative phosphorus loss assessment tool for agricultural fields

“…They concluded that BrayeKurtz and Mehlich III extractable phosphorus were not affected by incubation time except at very high rates. Koopmans et al (2004) found strong indications that the total pool of stable sorbed P (sum of reversibly adsorbed P and quasi-irreversibly bound P) to be close to equilibrium with the faster reacting P in a long term P uptake study on noncalcareous soils, indicating rapid P stabilization reactions. These studies suggest that the transfer between the active and stable pools to regain equilibrium may be faster than what the current SWAT routines allow.…”

Phosphorus Desorption Dynamics in Soil and the Link to a Dynamic Concept of Bioavailability

“…To estimate the total amount of P available for plant uptake and leaching, a desorption isotherm, describing the long-term equilibrium relationship between P in soil solution and the total pool of sorbed P, can be used. In a long-term pot experiment, where grass was cropped on a P rich acidic sandy soil to lower the soil P content, Koopmans et al (2004a) determined a desorption isotherm, which was described by the Langmuir equation. The total pool of sorbed P (P ox ) appeared to be close to equilibrium with P desorption in 1:10 (w/v) 0.01 M CaCl 2 extracts used to simulate conditions in the soil solution.…”

Distributed hydrological modeling of total dissolved phosphorus transport in an agricultural landscape, part II: dissolved phosphorus transport

“…264 W. D. Hively et al: Phosphorus transport in an agricultural landscape Kleinman and Sharpley, 2003); grazing (Smith and Monaghan, 2003); plant uptake (Koopmans et al, 2004); P mass balance and soil accumulation (Cassell et al, 1989); soil moisture and hydrology (McDowell and Sharpley, 2002b); soil type (Needelman et al, 2004) and management (Ginting et al, 1998;Klatt et al, 2003;Sharpley and Kleinman, 2003); temperature and precipitation (Correll et al, 1999); sorption kinetics (Morel et al, 2000;Schoumans and Groenendijk, 2000); and preferential flow and soil structure (Akhtar et al, 2003).…”