Cropping, soil type and manure application effects on phosphorus export and bioavailability

Abstract

Michaud, A. R. and Laverdière, M. R. 2004. Cropping, soil type and manure application effects on phosphorus export and bioavailability. Can. J. Soil Sci. 84: 295-305. A simulated rainfall study was conducted on an array of 36 runoff plots (6 m 2 each) deployed on three benchmark soil series of the Missisquoi region in southwestern Québec. The split-plot experimental design tested the effects and interactions of pig slurry treatment as main plots (check vs. 59 kg P ha -1 ) and cropping (tilled vs. hay) as subplots, on runoff volume and concentrations in total suspended sediment (TSS), total phosphorus (TP), dissolved reactive soluble P (DRP), particulate P (PP) and bioavailable P (BioP). TP concentration in runoff ranged from a low of 1.17 mg L -1 average on non-amended Bedford hay, to a peak concentration average of 9.55 mg L -1 on manured and tilled Saint-Sébastien plots. Variance analysis indicated significant contributions of treatments in explaining TP concentration in runoff as follows: Soil type effect > Cropping effect > Soil × Cropping interaction > Manure effect. Erosion and sediment transport processes were identified as prime vectors of TP export. Manure effect alone accounted for 35% of overall DRP variability, while soil type alone accounted for 70% of variability in particulate P bioavaibility (BioP/PP). Among practical implications of this study is the importance of assessing PP bioavaibility to adequately predict the adverse impact of runoff on aquatic ecosystems. The high level of interaction among cropping and manure treatment and the site-specific influence of soil physical and chemical properties also calls for a holistic approach to nonpoint P risk assessment and management, that focusses on timely manure P management, control of soil P build-up and agricultural practices minimizing surface runoff.Key words: Phosphorus, P-index, rainfall simulation, runoff, erosion, bioavailability, sediment Michaud, A. R. et Laverdière, M. R. 2004. Effets de la couverture végétale, de l'apport de lisier et du type de sol sur l'exportation de phosphore et sa biodisponibilité. Can. J. Soil Sci. 84: 295-305. Une étude faisant intervenir une simulation de pluie fut conduite sur un réseau de 36 parcelles expérimentales de 6 m 2 distribuées sur trois séries de sol caractéristiques de la région de Missisquoi, au Québec. Le dispositif expérimental en tiroirs a mis en relief les effets et les interactions des traitements d'apport de lisier de porc en parcelle principale (témoin vs. 59 kg P ha -1 ) et de couverture du sol en parcelle secondaire (sol nu vs. prairie) sur le volume de ruissellement et ses concentrations en matières en suspension (MES), phosphore total (PT), P réactif dissout (PRD), P particulaire (PP) et P biodisponible (Pbio). Les concentrations observées en PT ont varié d'un minimum de 1.17 mg L -1 sur le loam argileux Bedford en prairie, non amendé, à un maximum de 9.55 mg L -1 sur le loam Saint-Sébastien en condition de sol nu et amendé à partir de lisier de porc. L'analyse de variance indiqua que l...

Simulated impacts of climate change and agricultural land use change on surface water quality with and without adaptation management strategies

“…Approximately 70% of the TP loads from the annual crops were in the form of particulate P which is easily transported by surface runoff (Sharpley et al, 2002) and corresponded to periods of snowmelt. In southern Québec, snowmelt also corroborates with the peak TP transport (Michaud and Laverdière, 2004). The NO 3 À -N loads, on the other hand, were not correlated to streamflow but rather to months with the greatest increases in percolation.…”

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“…In fact, the Missisquoi Bay catchment was the source of nearly 25% of all P entering Lake Champlain during 2001 (Troy et al, 2007), 70% of which was derived from agricultural practices that emphasize high density feedlots, importation of nutrient-fortified grains, use of fertilizers in the production of silage, extensive drainage tiling, and application of manure directly to crop fields (LCBP, 2003;Sims et al, 1998). At present,~65% of nonpoint P influx to Missisquoi Bay is associated with livestock and manure application (Michaud and Laverdière, 2004). The St. Albans Bay catchment has experienced similar changes in agricultural practices, but has evolved to specialize more in regional hay and corn production than in direct milk production.…”

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“…In the soil, P combines with other ions to form insoluble compounds that can precipitate out of solution. This characteristic allows P to be available for transport, primarily by surface runoff (Michaud and Laverdière, 2004). Soluble forms of P that are plant available are the inorganic forms known as orthophosphates (H 2 PO 4 − or HPO 4 2− ).…”