Effective management of saline soils requires rapid, reliable methods of monitoring both soil water content (theta) and salt concentration, the latter measured in terms of electrical conductivity (sigma). This thesis examines estimation of theta, and bulk soil sigma (sigmaa) and soil water sigma (sigmaw), using time domain reflectometry (TDR). Calibration experiments were conducted in soil columns and in a vineyard that were irrigated with saline water. Within a theta range of 0.025--0.490 m3/m3, the correlation between TDR theta (thetaTDR) and gravimetrically determined theta (theta g) was high (r2 = 0.979 in soil columns, r2 = 0.836 in the field). The error of estimate of thetaTDR was 0.020 m3/m3 or less. Field thetaTDR estimates were sensitive to high salinity (sigmaw > 10 dS/m). Using a dual pathway parallel conductance (DPPC) model, sigma a was derived from sigmaw of saturated paste extracts and theta g. The correlation of TDR sigmaa to DPPC sigmaa was good in the laboratory (r2 = 0.915), and moderate in the field (r2 = 0.791), indicating a functional relationship between sigmaw and theta and TDR sigmaa. Models, to estimate sigmaw, were built by regression between paste extract sigma w and TDR sigmaa and thetaTDR. In a sigma w range of 3.0--23.4 dS/m in the columns, error of estimate of sigma w was small at 1.50 dS/m (+/-12.4% relative error range). In a sigma w range of 2.2--25.2 dS/m in the field, error of estimate of sigma w was 3.37 dS/m (+/-37% relative error range), which was significantly higher than the acceptable error range of +/-10%. ANOVA tests indicated that both TDR sigmaa and sigmaw·theta changed significantly with respect to the same sources of variance. Error in field estimates of sigmaw was associated with effects of salinity on thetaTDR and variability of soil conditions, particularly with respect to depth and time of sampling.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.30374 |
| Date | January 2000 |
| Creators | Entus, Jonathan. |
| Contributors | Bonnell, Robert (advisor) |
| 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 Agricultural and Biosystems Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001744261, proquestno: MQ64350, Theses scanned by UMI/ProQuest. |
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