Forms of phosphorus transfer in hydrological pathways from soil under grazed grassland

Abstract

Summary Phosphorus (P) from soil can impair the water quality of streams and lakes. We have studied the forms and pathways of its movement from soil to water using 1‐ha plot lysimeters, managed as grazed grassland for 12 months in temperate South‐west England. The water flow through three pathways, namely (i) surface plus interflow to 30 cm (on undrained soil), (ii) surface plus interflow to 30 cm (on a mole and tile drained soil), and (iii) mole and tile drains (to 85 cm), were gauged. Samples of water from each path were treated with various combinations of 0.45‐μm filtration and sulphuric acid‐persulphate digestion and molybdate reaction, to determine the different forms of P. The total P (TP) concentration was greatest in the surface plus interflow to 30 cm paths (means 232 and 152 μg l–1), whereas the mean concentration in the drainage to 85 cm was 132 μg l–1. This reflects the substantial enrichment of the Olsen‐P extracts from the surface horizons, as extracts from the 0–2 cm layer were 10‐fold more than below 45 cm. In all paths, the dissolved P comprised the greatest proportion of the P transferred, with dissolved reactive P being the dominant form. Draining land reduced the transfer of TP by about 30% (≈ 1 kg–1 ha–1 year–1), because it can be sorbed as it flows through soil to drains. All these concentrations could cause eutrophication in surface waters.

Effects of soil type on leaching and runoff transport of rare earth elements and phosphorous in laboratory experiments

“…According to previous studies, soils had strong capacity in retention and immobilization of REEs and P. It was found that over 99.5% of REEs and P were retained by soil particles after the exogenous rare earth elements were applied to soils, and only a very small amount remained in the soil solution (Jones 1997;Sharpley et al 2001). The adsorption rate was affected by soil clay minerals, pH, oxidation-reduction potential, organic matter, and cation exchange capacity (Haygarth et al 1998). Zhu et al (1996) studied the migration of exogenous REEs through the leaching process in soil columns and performed numerical simulation.…”

“…Phosphates can be readily adsorbed by soil particles (clay mineral surfaces and amorphous oxy-hydroxides), precipitated by common soil cations (Al, Ca, Fe), or immobilized by microorganisms after a series of chemical, biological, and physical reactions. There are many studies on phosphorus losses from agricultural sources, their pathways, and rates (Haygarth et al 1998), but the key mechanisms of phosphorus transport in different types of soils remain unclear.…”

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

“…Phosphorus sources can be natural (indigenous soil P and atmospheric deposition) and anthropogenic (fertilizers and animal feed input to the farm, fertilizers and manure applied to the soil). Most research examining diffuse P sources has been conducted in intensively managed agro-ecosystems, where continued inputs of P as mineral fertilizers and imported animal feed result in the accumulation in topsoil (Condron, 2004;Haygarth et al, 1998a). Imported feed is particularly important in areas of intensive livestock production where large quantities of manure are applied to land (Sharpley and Tunney, 2000).…”

“…Further complexity arises because P is usually deposited and entrained during transport (Jarvie et al, 2002c;Neal et al, 2002) and can change form in space and time. While some plot scale work has examined the controls on the transport at scales up to 1 ha (Haygarth et al, 1998a), scaling-up this work to delivery to surface and groundwater at the hillslope or catchment scale is complex (Beven et al, 2005) and cannot be easily be quantified because of the nature and complexity of the flow paths . During delivery, the extent, nature, and dynamics of interactions between soluble and particulate forms in water and sediments play a critical role, and are an important consideration in developing effective strategies for mitigation of accelerated P transfer (Baldwin, 1996;McDowell et al, 2001McDowell et al, , 2004.…”

Impact of chemically amended pig slurry on greenhouse gas emissions, soil properties and leachate

“…This is in agreement with McDowell et al (2004), who found that more TP was lost as PP in overland than subsurface flow due to the higher kinetic energy and erosive power of high-frequency storms. Loss of P in subsurface flow is generally less than that in runoff, and will decrease as the degree of soil-water contact increases, due to sorption by P-deficient subsoils (Haygarth et al, 1998;McDowell et al, 2004). Although a soil with a low Pm (3.21±0.29 mg L -1 ) was used in this experiment, its high adsorption capacity for P (0.224 g P kg -1 ) and low EPC 0 (0.513 mg L -1 ) facilitated adsorption of P during leaching.…”