Soil and land use effects on phosphorus in six streams draining small agricultural catchments in Scotland

Abstract

Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland.The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stockedlarable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.Larger mean annual concentrations were seen in the west (0.076-0.142 mg P04-P/l as molybdate-reactive phosphate-MRP) compared with the northeast (0.012-0.025 mg PO,-P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn.

Evaluating diffuse and point phosphorus contributions to river transfers at different scales in the Taw catchment, Devon, UK

“…These high concentrations could alternatively arise if at these times there were inputs of solute-rich, long residence time throughflow to the river, subject to only low rates of dilution (e.g. Hooda et al, 1997). There was however little evidence of such pathways and inputs in the Taw catchment, owing to its low storage capacity.…”

“…McGuckin et al, 1999;Viney et al, 2000;Wade et al, 2002) and field studies (e.g. Vighi and Chiaudani, 1985;Hunsaker and Levine, 1995;Smith et al, 1995;Heathwaite et al, 1996;Hooda et al, 1997) that diffuse P transfer significantly affect river P fluxes. However, the routing of P from the point of mobilisation to the point of delivery to water is complex.…”

Phosphorus species and fractionation – Why sewage derived phosphorus is a problem

“…As shown in Table 2, agricultural inputs to water bodies from field runoff contains a high percentage of PP, and TDP concentrations are significantly different from SRP (Jarvie et al, 2006;Hooda et al, 1997;Edwards and Hooda, 2008). This higher proportion of PP in agricultural source P, and the greater proportion of dissolved organic P within the TDP fraction, means overall a lower fraction of TP is bioavailable than that from STW derived TP where SRP is the dominant species.…”

Relation entre la richesse du sol en phosphore et la concentration en phosphore de l'eau de drainage dans deux agro-écosystèmes

“…La pédogènese pourrait également être impliquée. HOODA et al (1997) rapportent des pertes quatre fois plus faibles dans les podzols bien drainés que dans les gleysols. Les résultats de notre étude indiquent que les systèmes culturaux (type de culture, apports répétés de déjections animales, fréquence de labour) pourraient avoir une influence encore plus grande sur la teneur en P de l'eau de drainage.…”

“…La relation entre le DSPS 0X et P, n'est pas significative. Les faibles coefficients de corrélation observés entre les mesures de sol en P et la teneur en P t de l'eau de drainage montrent bien la difficulté de prédire celle-ci dans des sols contrastants (HOODA et al, 1997 ;BEAU-CHEMIN ef al., 1998). Des facteurs de gestion tels le nombre de jours depuis la fertilisation peuvent avoir un effet plus grand que la richesse du sol sur le P t de l'eau de drainage (NASH étal., 2000).…”