A field experiment was conducted on a homogeneous sandy soil and a layered soil of southern Quebec from 1988 to 1990. This was done in order to evaluate the yield response of indeterminate soybean to subsurface irrigation and to determine the performance of subsurface irrigation in a layered soil. It was found that indeterminate soybean varieties increase their yield by approximately 30% for two out of three years. Soybean are very sensitive to competition between themselves as well as with weeds. This sensitivity is increased during subsurface irrigation. Weeds were more prominent in the irrigated area. It was concluded that the soybean yields are functions of water table depth, percent weed and plant population density. The minimum allowable water table depth for soybean was found to be 45 cm. At a water table depth greater than 95 cm no yield response was observed. / Water table management is not only possible but very functional in the layered soils of southern Quebec. It was found that surplus water did not drain from the irrigated area until the water table anywhere in this area was 10 cm higher than the elevation of the overflow pipe in the control chamber. It was therefore concluded that a water table depth range of 10 cm should be included in the design of the water table control system to allow for the effects of rain.

No description available.

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.

The North American cranberry plant (Vaccinium macrocarpon Aiton) is a wetland crop species grown commercially in natural or constructed peat or sandy soil basins. Since production is highly water dependent, water requirements are very significant and have prompted growers to explore new water management practices to improve irrigation efficiency and protect water resources. One way of conserving and better managing water, given the infrastructure in place, would be to develop sub-irrigation. / The design of a subsurface irrigation system requires the evaluation of various soil properties. This was undertaken at four established cranberry production sites, situated near Saint-Louis-de-Blanford, Quebec. Two of the fields contained a sandy soil, and the other two were peat soils. Soil physical properties measured included: saturated hydraulic conductivity, bulk density, porosity, soil moisture characteristic curves and particle size distribution.

The overall goal of this study was to investigate the possibility of reducing NO3-- concentration in the lower soil horizon by promoting denitrification. The study looked at an inexpensive remediation practice for subsurface-drained fields in order to degrade N0j' and consequently diminish NO3-- pollution. The experiments were conducted on a corn field at the Macdonald Campus Farm. The field was composed of sandy loam soil underlined by a clay layer. / In this study, sucrose was injected at a concentration of 20 mg L --1 within the subirrigation water. Furthermore, the water table was maintained at approximately 70 cm from the soil surface in order to create an anaerobic environment that allows for denitrification. The purpose was to furnish dissolved organic carbon (DOC) to the resident microorganisms in order to carryout a higher amount of denitrification. / The NO3-- levels in ground water were monitored weekly. Gas samples were taken from the field to observe whether N2O emissions increased as a result of the treatment This was considered to be important since N2O is a greenhouse gas. / It was found that the addition of sucrose significantly resulted in a faster rate of denitrification. The higher biological activity severely damped the NO3-- peaks in the subsoil, which arose following major rainfall events. / The addition of sucrose at 20 mg L--1 was found to be significant in lowering the amounts of released N2O. Therefore, adding DOC in the subirrigation water not only helped remediate water contamination but also served as a remedy to atmospheric pollution. / In addition, the hydraulic conductivity of the soil was monitored to ensure that no bioclogging arose from an anticipated rise in the bacterial population due to the addition of sucrose. It was found that the addition of sucrose at 20 mg L--1 did not contribute in anyway to reduce the soil's hydraulic conductivity.

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.

Subirrigation systems are generally used in humid areas to provide suitable moisture conditions for plant growth. These systems can also be used to reduce pesticide loadings from agricultural lands, since they tend to keep the discharging waters within farm boundaries for extended periods of time. This allows for greater pesticide microbial and chemical degradation. / A three-year field lysimeter study was initiated to investigate the role of subirrigation systems in reducing the risk of water pollution from the three most commonly used herbicides in Quebec, namely atrazine (2-chloro-4[ethylamino]-6[isopropylamino]-1,3,5-triazine), metribuzin (4-am ino-6(1,1-di meth yl eth yl)-3-(meth yl thio)-1,2,4-tria zin-5(4H)-one), and meto lach lor (2-chlo ro-N-(2-eth yl-6-methyl phen yl)-N-(2-meth oxy-1-meth yl eth yl)acet amide). Eighteen PVC lysimeters, 1 m tall x 0.45 m diameter, were packed with a sandy soil. Three water table management treatments, i.e. two subirrigation treatments with constant water table depths of 0.4 and 0.8 m, respectively, and a free drainage treatment in a completely randomized design with three replicates were used. Grain corn (Zea mays L.) and potatoes (Solanum tuberosum L.) were grown on lysimeters, and herbicides were applied each year at the locally recommended rates at the beginning of each summer. Soil and water samples were collected at different time intervals after each natural or simulated rainfall event. Herbicides were extracted from soil and water samples and were analyzed using Gas Chromatography. / From the three years results (1993--1995), it has been concluded that all three herbicides were quite mobile in this sandy soil, as they leached to the 0.85 m depth below the soil surface quite early in the growing season. This suggests that if the drainage effluent or seeping waters from sandy soils of agricultural lands in southern Quebec drain freely, they may be considered to be a serious non-point source of pollution to the water bodies. The results have also shown that herbicide concentration decreased with soil depth as well as with time, meaning that the higher herbicide residues were found at top layers, and soon after the herbicide application. The herbicide mass balance study revealed that when the drainage effluent was kept within the lysimeters under the subirrigation setup, there was a statistically significant reduction of atrazine and metribuzin residues (shorter half lives) in the adsorbed and liquid phases. However, the reduction in metolachlor concentration under the subirrigation system was not statistically significant. These findings suggest that subirrigation, combined with certain herbicides can significantly reduce the herbicide loadings from corn and potato farms in southwestern Quebec, and become environmentally beneficial. / A computer simulation model (PRZM2), was used to simulate atrazine, metribuzin, and metolachlor leaching in the lysimeters, under subsurface drainage conditions. The simulated values for all three chemicals in most of the cases followed the leaching pattern of observed data. But the model either under- or over-estimated the herbicide concentrations in the soil. This could have been caused by simplistic instantaneous linear adsorption/desorption of herbicides, and inadequacy of conventional Darcian approach for the treatment of matrix flow.

Field water table measurements were taken at two sites in Southern Quebec in order to validate DRAINMOD, a field scale water table management model. Two growing seasons of data were collected on a loamy sand soil near Sorel, Quebec and one year of data on a clay soil to the south-west of Montreal. Several water table management schemes were investigated, ranging from conventional subsurface drainage to automated subsurface irrigation. / DRAINMOD was used to simulate the measured water table fluctuations and relative corn crop yields over the growing season. Verification of the model was needed to determine if it could be a useful tool in the design and operation of water table management systems for the Quebec region. / It was found that DRAINMOD output closely simulated the water table fluctuations for conventional drainage and subsurface irrigation plots provided no exceptional circumstances existed. More study is needed in some areas such as bedded fields and in the use of fluctuating water level control structures.