The effect of soil type on phosphorus sorption capacity and desorption dynamics in Irish grassland soils

Abstract

Abstract. The phosphorus (P) sorption and desorption dynamics of eleven major agricultural grassland soil types in Ireland were examined using laboratory techniques, so that soils vulnerable to P loss might be identified. Desorption of P from soil using the iron‐oxide paper strip test (Pfeo), water extractable P (Pw) and calcium chloride extractable P (Pcacl2) depended on soil P status in all soils. However, soil types with high organic matter levels (OM), namely peat soils (%OM >30), had lower Pfeo and Pw but higher Pcacl2 values compared to mineral soils at similar soil test P levels. Phosphorus sorption capacity remaining (PSCr) was measured using a single addition of P to soils and used to calculate total P sorption capacities (PSCt) and degree of P saturation (DPS). Phosphorus sorption capacities correlated negatively with % OM in soils indicating that OM may inhibit P sorption from solution to soil. High organic matter soils exhibited low P sorption capacities and poor P reserves (total P, oxalate extractable P) compared to mineral soils. Low P sorption capacities (PSCt) in peat soils were attributed to OM, which blocked or eliminated sorption sites with organic acids, therefore, P remained in the soil solution phase (Pcacl2). In this work, peat and high organic matter soils exhibited P sorption and desorption characteristics which suggest that these soils may not be suitable for heavy applications of manure or fertilizer P owing to their low capacities for P sorption and storage.

The phosphorus transfer continuum: Linking source to impact with an interdisciplinary and multi-scaled approach

“…There is strong evidence to suggest that the potential for solubilisation increases with increasing concentrations of extractable soil P. In particular, there has been substantial interest in threshold soil P concentrations, above which transfer in drainage water increases at a much greater rate (Heckrath et al, 1995). These threshold concentrations have been termed dchange pointsT, and may be used to assess the potential for P transfer from soil in runoff water (Blake et al, 2002;Daly et al, 2001;Maguire and Sims, 2002). These findings indicate that soil test P concentrations and the degree of saturation can be used to predict the risk of transfer by surface or subsurface hydrological flow paths.…”

A review of phosphorus and sediment release from Irish tillage soils, the methods used to quantify losses and the current state of mitigation practice

“…The current agronomic optimum P m value for Irish soils is 6mg l −1 for grass production (Daly et al 2001 (Daly et al 2001). Maintenance of the P fertility of arable soils is important, as cereal crops perform better in soils with good P status (6.1-10.0mg l −1…”

Influence of Incubation Period, Temperature and Different Phosphate Levels on Phosphate Adsorption in Soil

“…Soluble P compounds when added to soil react rapidly with various compounds like CaCO 3 (Bertrand et al, 2003), sand (Leclerc et al, 2001), clay (Johnston et al, 1991;Toor et al, 1997), organic matter (Daly et al, 2001), iron and aluminum oxides (Toor et al, 1997) and are quickly converted to slowly available forms (Castro and Torrent, 1995). In addition to these properties, adsorption also depends on contact time between soil and P with temperature (Indiata et al, 1999).…”