Four ponded depressional areas were selected in a cultivated field near Ste-Agnes de Dundee, Quebec. In 1988, land, soil, water and crop parameters were measured under ponding and non-ponding conditions in order to formalate a drainage investigation procedure for ponded depressions. / A sweet corn yield reduction of 39% was measured in depressions compared to ridges; this yield reduction occurred with 3 to 5 year interval of recurrence rainfalls. Loss of yield in depressional areas gave an overall reduction of 5% for the whole field. There was an additional loss in quality from poor uniformity of the corn cobs. The Ste-Agnes corn yield was estimated at 20% of the regional average. There was no significant difference between soil characteristics in depressions and ridges except for hydraulic characteristics such as infiltration and percolation rates as determined with the infiltrometer, and hydraulic conductivity as determined with the auger hole method. / The ponding runoff coefficients (mean PRC = 0.11) measured during the summer of 1988 were similar to the ones (mean PRC = 0.13) calculated using the CN curve method (USDA, SCS). / The low percolation rate of the subplow layer was found to be the main constraint to the subsurface drainage of the ponded depressions. / Soil survey and ponding study results were used to formulate a drainage investigation procedure for ponded depressional areas in the St. Lawrence Lowlands.

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The performance of a subsurface irrigation system in a clay soil was investigated under field conditions from 1989 to 1991. It was found that subsurface irrigation could be practised successfully in some clay soils of Quebec. The 10 m drain spacing was found to be better than the 20 m drain spacing in terms of keeping a uniform water table between the drains. The water table distribution between the drains was found to be a factor of the applied hydraulic head. The relationship between the applied hydraulic head and the midspan water table elevation could not be determined due to unfavourable weather conditions during the study period. The soil moisture content was found to follow the same behavior as the water table elevation, however, the relationship between these two parameters could not be properly established. It was also found that under the same applied hydraulic head, the drain spacing did not affect the soil moisture distribution. Subsurface irrigated plots were found to make better use of rain water than drained only plots since they did not permit the formation of well-defined pathways (macropores) allowing rainfall to move below the root zone without wetting it. It was also found that subsurface irrigation did not alter the soil structure appreciably and that autumn drainability was not affected in 1990 and 1991.

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No description available.

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Field experiments were conducted on St-Samuel sandy loam soil in 1982 and 1983, with eight replicates of irrigated and non-irrigated maize plots. Soil moisture regime, root density and maize yields were determined to demonstrate the effect of subsurface irrigation and drainage systems. / Laboratory experiments were conducted on large and small undisturbed soil cores to determine pertinent soil properties, relating drainable volume and steady upward flux to water table depth. / A water balance model was developed and used with a stress-day-index to predict water table depth, excessive and deficit soil moisture conditions and effects on corn yield. Economic analyses were made to identify subsurface irrigation/drainage designs which optimize the profit for a corn crop. / A simple method based on first and second order moments was proposed to determine the effects of parameter uncertainty in the relationship of steady upward flux vs water table depth on subsurface irrigation/drainage design parameters. / Based on the above information, a realistic subsurface irrigation/drainage design was proposed and operational recommendations were made for an example field.

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.