Water table management (WTM), consisting of controlled drainage and subirrigation, can significantly reduce nitrate losses through subsurface drainage. However, recent research showed that this system could increase phosphorus (P) losses in tile drains. The cause of this increase, whether related to enhanced P solubility due to shallow water tables seen with WTM or to the addition of P by the subirrigation water, has not been investigated. / The goal of this research was to evaluate the impact of WTM on P losses and on soil P concentration, soil P saturation and soil pH with a field study. Furthermore, a laboratory soil column study was conducted to better understand the results of the field study. / The field study was carried out in 2004 and 2005 in Coteau-du-Lac (Quebec). The WTM system, with a design water table set at 0.60 m below the soil surface, was compared to conventional free drainage (FD). The results showed that WTM had no effect on the soil P concentration and saturation. However, soil pH was slightly increased in WTM plots, which may demonstrate a greater P solubility. Total outflow volumes from WTM plots were reduced by 19% and 27% in 2004 and 2005, respectively. However, P loads in drainage water from plots under WTM were greater than from FD plots due to increased P concentrations, which always exceeded Quebec's surface water quality standard of 0.03 mg/L. Of the total P concentration, around 96% was dissolved P in both treatments. / The laboratory soil column experiment, in which the two drainage treatments were simulated, also showed that P concentrations were greater under WTM than FD. This suggests that the increased P losses in the field with WTM were most likely caused by the increased P solubility due to a shallow water table rather than by the addition of P by the water used for subirrigation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.98722 |
| Date | January 2006 |
| Creators | Hebraud, Caroline. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Bioresource Engineering.) |
| Rights | © Caroline Hebraud, 2006 |
| Relation | alephsysno: 002481607, proquestno: AAIMR24691, Theses scanned by UMI/ProQuest. |
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