Processes Governing Phosphorus Availability in Temperate Soils

Abstract

Phosphorus losses from agricultural soil to water bodies are mainly related to the excessive accumulation of available P in soil as a result of long-term inputs of fertilizer P. Since P is a nonrenewable resource, there is a need to develop agricultural systems based on maximum P use efficiency with minimal adverse environmental impacts. This requires detailed understanding of the processes that govern the availability of P in soil, and this paper reviews recent advances in this field. The first part of the review is dedicated to the understanding of processes governing inorganic P release from the solid phase to the soil solution and its measurement using two dynamic approaches: isotope exchange kinetics and desorption of inorganic P with an infinite sink. The second part deals with biologically driven processes. Improved understanding of the abiotic and biotic processes involved in P cycling and availability will be useful in the development of effective strategies to reduce P losses from agricultural soils, which will include matching crop needs with soil P release and the development of appropriate remediation techniques to reduce P availability in high P status soils. SOILS contain between 100 and 3000 mg P kg" 1 soil, most of which is present as orthophosphate compounds. The proportion of total soil P present in organic forms ranges from 30 to 65% (Harrison, 1987). The soil solution in agricultural soils, which is the main source of P for plant roots, contains between 0.01 and 3.0 mg PL"1 . The quantity of P present in the soil solution represents only a small fraction of plant needs, and the remainder must be obtained from the solid phase by a combination of abiotic and biotic processes. The pro- cesses involved in soil P transformation are precipitation-dissolution and adsorption-desorption which control the abiotic transfer of P between the solid phase and soil solution, and biological immobilization-mineralization processes that control the transformations of P between inorganic and organic forms (Fig. 1).Phosphorus losses from soils occur by leaching at very low rates in undisturbed ecosystems (Walker and Syers, 1976; St. Arnaud et al., 1988; Frossard et al., 1989; Letkeman et al., 1996). The implementation of intensive agricultural production has markedly increased P losses from soils through increased runoff, erosion and leaching, which in turn can have adverse effects on water quality. These losses are further increased by the excessive accumulation of bioavailable P in the upper soil horizons, due either to application of inorganic and/or organic P fertilizers in excess of plant needs and/or to inappropriate fertilizer applications (Braun et al., 1994; Beaton et al., 1995; Sharpley et al., 1995; Sharpley and Rekolainen, 1997; Sibbesen and Runge-Metzger, 1995; Sibbesen and Sharpley, 1997; Daniel et al., 1998; van der Molen et al., 1998).It is the hypothesis of this paper that an efficient way of reducing P losses to the environment while maintaining an optimum plant production is to co...

Differences in Soil Physical and Chemical Properties of Rehabilitated and Secondary Forests

“…The concentrations of P in soils depends on a combination of factors including plant uptake, adsorption-desorption and dissolutionprecipitation of inorganic P, the mineralization of organic P and microbial immobilization and fertilizer addition (Perrott et al, 1990;Frossard et al, 2000).…”

Effects of Pig Slurry Application and Crops on Phosphorus Content in Soil and the Chemical Species in Solution

“…In soil, P is adsorbed to the functional groups of inorganic particles, forming an inner-sphere complex (Barrow, 1983) and therefore, P mobility and concentration in the soil solution are low (Frossard et al, 2000). However, when P is added successively and at high rates to the soil, for example by PS application in crop conservation systems such as no-tillage (NT), where the soil is not tilled, the total P content may increase (Berwanger et al, 2008;Lourenzi et al, 2014), and especially the content available to plants, which can be diagnosed by the method of Mehlich-1 (Gatiboni et al, 2008;Guardini et al, 2012).…”

Evaluating phosphorus loading from repeated manure applications to two Saskatchewansoils

“…Phosphorus is present in the soil primarily as orthophosphate compounds (Frossard et al 2000), many of which have low solubility and plant availability. Labile P may be defined as the inorganic and readily mineralized organic P fractions that are present in, and contribute to, soil solution P and its availability for plant uptake.…”