Papers by Suzanne Allaire
Preferential flow processes, such as crack flow (CF), burrow flow (BF), finger flow (FF) and late... more Preferential flow processes, such as crack flow (CF), burrow flow (BF), finger flow (FF) and lateral flow (LF) are known as factors enhancing phosphorus (P) transport from agricultural soils to water bodies. The objective of this study was to develop a methodology for predicting the likelihood of preferential flow processes in agricultural soils at the landscape scale and their potential occurrence around the Canadian Great Lakes. The methodology considered climate, soil and crop parameters and a water budget that calculated surface runoff and drainage. Crack flow largely depended upon soil clay content, BF on soil texture and climate, FF on layering in sandy soils and LF on the presence of trees, slope and soil restricting layers. Crack flow had a high likelihood to occur southern Lake Ontario and all around Lake Erie. A high likelihood of FF could be found in the area where CF was low (i.e., in the sandy soils north of Lake Huron and Lake Ontario). Burrow flow had a medium likelihood to occur on Manitoulin Island and close to the shoreline north of Lake Ontario. Medium to high likelihood of lateral flow might occur in the area south of Lake Ontario, west of Toronto in a narrow band towards Lake Huron, and to a lesser extend in a large area northeast of Lake Huron. Lateral flow may transport soluble P in areas where P was previously carried downward by FF from inland (in soils) to surface water bodies. In several areas, tile drainage may transport all forms of P carried downward from the soil surface to the subsurface by CF and BF to lake tributaries. Preferential flow distribution maps could be used as tools for supporting the identification of agricultural lands where management might enhance subsurface processes of P transport toward groundwater or surface water bodies.
The indicator of risk of water contamination by phosphorus (IROWC_P)
was designed to estimate the... more The indicator of risk of water contamination by phosphorus (IROWC_P)
was designed to estimate the level of risk of P contamination in water and how the level of risk has changed over 25 yr
(19812006) in agricultural watersheds of Canada. IROWC_P allows for a qualitative assessment of this risk in
comparison with other regions of eastern and western Canada, and the identification of high to very high risk watersheds
may require on-site assessment and the development of remedial action plans. This study presents an in-depth analysis of
IROWC_P results in the major Great Lakes watersheds of Canada. The risk of water contamination by P remains
acceptable (very low to moderate) in most Great Lakes watersheds, but better management practices (e.g., reduced
fertilization and manure application rates) and improved control of surface runoff may be required in watersheds which
are at increased risk. The Canadian watersheds of the Great Lakes basin showed a 39% reduction in their P applications in
excess of crop requirements between 1981 and 2006 bringing the Ontario provincial P-balance close to equilibrium in 2006.
Vulnerable areas were found south of Kitchener in the Lower Grand River watershed and east of Lake Simcoe.
Finger flow (FF) and lateral flow (LF) are key pathways connecting sub-surface contaminant transp... more Finger flow (FF) and lateral flow (LF) are key pathways connecting sub-surface contaminant transport
from soils to water bodies. The objectives of this study were to develop methodologies for predicting
the likelihood of FF and LF occurrence in agricultural soils across Canada at the landscape scale, and to 29
use them as input parameters for risk indicators of water contamination. Both FF and LF consider the vol-
ume of infiltrating water. FF considers soil texture, layering, and content in coarse fragments, while LF
considers restricting layers, trees, slope, and soil depth. High risk of LF in British Columbia is associated
to shallow soils over compacted till in steep areas with higher density of trees. South of the St. Lawrence
River shows the largest region at high risk of LF due to much water infiltration, compacted till and shal
low soils. Eastern provinces have higher risk of FF, due to layered sandy soils and abundant precipitations.
LF and FF distribution maps can also be used as simple tools for supporting the identification of land sur
faces where management should consider subsurface contaminant transport processes and to warn
potential water pollution from inland agricultural contaminants.
Le mouvement de gaz dans les sols a un rôle important à jouer en environnement, entre autres, dan... more Le mouvement de gaz dans les sols a un rôle important à jouer en environnement, entre autres, dans les écosystèmes tant urbains que naturels, les productions agricoles, horticoles et forestières, la décontamination de sites, les changements climatiques (gaz à effet de serre (GES)), etc. Les échanges gazeux sol-atmosphère dépendent en partie de la dynamique des mouvements de gaz dans les sols. En horticulture comme en agriculture, ces échanges gazeux jouent un rôle écologique important notamment pour la croissance des plantes, pour les cycles de l'eau, de l'oxygène, du carbone et de l'azote. Le mouvement de gaz dans le sol et les échanges sol-atmosphère sont influencés par la capacité du sol à stocker et à transporter le gaz : 1) La capacité de stockage, qu'on appelle la porosité en air, fait référence aux particularités du système poral telles que taille, tortuosité, continuité des pores et est fonction des caractéristiques physiques du sol telles que la densité et l'humidité. 2) Les capacités de transport et d'échanges sol-atmosphère sont fonction de deux mécanismes physiques majeurs: la convection et la diffusion. Le mouvement convectif, souvent négligeable, dépend des variations de pression barométrique, de température, de la teneur en eau et du vent à la surface du sol, alors que le mouvement diffusif est essentiellement dépendant du gradient de concentration entre le sol et l'atmosphère, lui-même fonction de la production et de la consommation des gaz par la biomasse du sol. Actuellement au Québec, des recherches impliquant le mouvement de gaz dans les sols sont menées à l'Université Laval en collaboration avec l'Université de Sherbrooke, l'Université de Montréal, Agriculture et Agroalimentaire Canada, les villes de Québec et de Saint-Nicéphore ainsi que l'entreprise Patates Dolbec de Saint-Ubalde. Une partie de ces recherches vise à caractériser la variabilité spatio-temporelle des émissions de GES par des sols agricoles. Les résultats permettront une gestion améliorée des pratiques culturales (fertilisation, travail du sol, etc.) et une amélioration conséquente de l'évaluation des quantités de GES émises par les sols agricoles. Un autre projet de recherche consiste à diminuer les émissions de méthane par les sites d'enfouissements en optimisant les conditions physiques du sol de recouvrement afin d'oxyder ce gaz par la flore bactérienne. En effet, les sols contiennent des microorganismes qui peuvent aussi bien dégager du méthane ou en consommer en le transformant en dioxyde de carbone. Un autre projet traite de la quantification des émissions de GES par des gazons urbains afin de choisir la gestion des espaces verts minimisant la production de gaz à effet de serre. Les émissions de gaz par les sols étant directement reliées aux mouvements et au stockage de gaz dans les sols, il faut donc, tant pour l'environnement que pour les plantes, affiner nos connaissances sur les processus physiques et les phénomènes naturels responsables des mouvements de gaz.
Passive methane oxidation biocovers (PMOB) have been recently proposed as a viable option for mig... more Passive methane oxidation biocovers (PMOB) have been recently proposed as a viable option for migration residual emissions. The efficiency of a PMOB depends on the degree of saturation, which controls the migration of molecular O2; a necessary element in the CH4 oxidation process. The evolution of the degree of saturation Sr is regulated by the unsaturated flow of moisture across the PMOB, which can only be describe with the water retention curve (WRC) and hydraulic conductivity function (k-fct) of the material. This paper discusses the reliability of laboratory-obtained WRCs as input parameter in the prediction of the hydraulic behavior of PMOBs in the field. Three WRC were determined based on field data and in the laboratory using a tension plate. The field data was obtained from an experimental PMOB constructed at St-Nicéphore landfill, Quebec, Canada, where tensiometers and water content probes were installed.
This research compared four turfgrass lawn management approaches on CO2 emissions: (1) fertilized... more This research compared four turfgrass lawn management approaches on CO2 emissions: (1) fertilized and frequently mowed with clippings removal, and unfertilized with clippings left on site and mowed 2) weekly, 3) three times, or 4) once during the growing season. CO2 emissions were measured weekly with flux chambers. Mowing frequency had higher impact on CO2 flux than fertilisation and soil characteristics. Frequently mowed sites emitted CO2 at a maximum rate of 0.63 mg m-2 s-1 and annually up to 2.0 kg m-2, an emission four times higher than lawns mowed infrequently. Differences between treatments mostly occurred during warm weeks.
Methane oxidation within a passive methane oxidation barrier (PMOB) and the downward migration of... more Methane oxidation within a passive methane oxidation barrier (PMOB) and the downward migration of molecular O 2 , whose presence is necessary for the oxidation reaction to occur, were simulated using the finite element simulator TOUGH2-LGM. The goals of the study were to validate the use of TOUGH2-LGM by reproducing real field profiles obtained under different conditions and to evaluate the depth of O 2 penetration under several conditions. TOUGH2-LGM handles both advective and diffusive gas fluxes. The oxidation reaction was simulated by imposing a Neumann condition, i.e. CH 4 was extracted from predetermined elements. The main variables of concern were the degree of water saturation of the PMOB, the pressure differential between its base and the surface, the position and thickness of the oxidation front and, finally, the oxidation rate, i.e. the rate at which CH 4 was removed from the system. Other important variables, such as the gas permeability and diffusion coefficient were obtained in the laboratory. Inspection of the results shows that TOUGH2-LGM was able to quite accurately reproduce the field profiles. The simulator also makes it possible to predict the depth of O 2 penetration as a function of pressure differential and humidity within the PMOB. This type of information is fundamental for the design of effective biocovers.
The greenhouse industry needs renewable, cheap, and available substitutes for rockwool. The physi... more The greenhouse industry needs renewable, cheap, and available substitutes for rockwool. The physical properties and performance of rockwool substitutes such as low grade peat, composted bark white spruce and fir, shavings, sawdust, and peat-bark mixtures were compared during two greenhouse experiments with tomato grown in plastic bags. Air and water filled porosities greatly differed between substrates, particularly for sawdust and shavings. Relative gas diffusivity (Ds/Do) and the hydraulic conductivity were less different between substrates. The physical properties of the substrates changed over a production cycle but the changes were small compared to treatment differences. Yields in peat-bark substrates were similar to rockwool substrates during both the short and long experiments but were lower in sawdust and shavings during the long experiment. The yield differences expected between media were less than the differences between some substrate physical properties of the various media. Yields were positively related to easily available water (EAW) and negatively related to Ds/Do and airfilled porosity (AFP). This indicated excessive drainage for the low-yielding substrates. In plastic bags, media properties related to aeration were not good indicators of production because the plants adapted to the lack of aeration by modifying their root distribution. White spruce and fir bark alone or mixed with low grade peat showed high potential for greenhouse tomato production and represent an environmental sound alternative to rockwool.
Aeration is a critical factor of substrate performance for container grown plants. In a 14-mo nur... more Aeration is a critical factor of substrate performance for container grown plants. In a 14-mo nursery study, although air filled porosity dropped below optimum values, the gas relative diffusivity was unaffected, as a result of an increase in pore effectiveness. This indicates that, contrary to the general belief, aeration properties of potting substrates may not deteriorate with time.
Large quantities of gases emitted by landfills move through their cover material mainly by convec... more Large quantities of gases emitted by landfills move through their cover material mainly by convection and diffusion. Diffusion is important for lateral flow of gas and is primordial for O2 movement to support CH4 oxidation. Five laboratory methods used for measuring the relative gas diffusion coefficient (Ds/Do) were compared. All methods gave similar Ds/Do. Long soil columns in closed system result in slightly higher Ds/Do, probably due to boundary effect. Methods with transient boundary conditions are simpler. Larger cores allow the study of heterogeneity in gas movement, important in landfill cover materials, but initial and boundary conditions are more difficult to control. When macropores are involved, the Millington-Quirk model (1960) better predicted the Ds/Do measured with the different methods. However, the Moldrup et al. (2000) model best predicted all Ds/Do when macropores were not considered. There were no obvious trends of model performance relative to specific measuring methods.
The impact of macropore description on solute transport predictions in soils is not well understo... more The impact of macropore description on solute transport predictions in soils is not well understood. A 2-D Galerkin finite element model was used to compare different approaches for describing macropore flow in soil. The approaches were: a modification of the hydraulic conductivity function (Hydraulic function), the lumping of all macropores into one single straight macropore (Lumping), the use of an exchange factor between microporosities and macroporosities that occupy the same area (Dual porosity), and a detailed description of each macropore (Full description, base case). Simulated breakthrough curves were obtained with domains that contained one or more macropores of different shapes under both steady state and transient flow conditions. The Hydraulic function approach was not sensitive to macropore continuity and tortuosity. When the macropores were open at the soil surface and the solute was surface applied, the first three approaches underestimated both breakthrough curves and solute distribution in the profile compared to the Full description approach. When the solute was initially incorporated in the soil, the first three approaches overestimated the breakthrough curves compared to the Full description approach. The first three approaches also underestimated the heterogeneity of solute distribution in the profile compared to the Full description approach, mostly when the macropores were tortuous. The differences between predicted breakthrough curves with different approaches decreased with an increase in tortuosity and a decrease in surface continuity. To simplify macropore description, the Dual porosity approach was the better of the first three approaches for predicting breakthrough.
Models developed for solute transport vary in their assumptions on macropore continuity and tortu... more Models developed for solute transport vary in their assumptions on macropore continuity and tortuosity. It is unclear how much simplification can be made in computer models to characterize macropore effects on water and solute transport through soils. The objectives of this study were to assess how the importance of macropore continuity and tortuosity varies (1) with various initial and boundary conditions (this paper) and (2) with simplifying model assumptions for macropore description (companion paper). The above assessments were made with a computer model based on 2- D Galerkin finite element solution of Richards’ equation for water flow and convective–dispersive equation for solute transport. The model can simultaneously handle macropores of varying length, size, shape, and continuity. Model predictions were in agreement with laboratory data for different macropore shapes and continuities under transient flow conditions. Simulations for various initial and boundary conditions showed that surface connected macropores under ponded conditions and under high intensity rainfalls favored the rapid transport of solutes. However, solute transport was delayed if the solute was initially incorporated in the soil even when macropores were connected to the soil surface. Macropores not connected to the soil surface only slightly accelerated solute transport for any boundary conditions. Macropore tortuosity did not influence breakthrough curves as much as the continuity but greatly influenced solute distribution in the profile. The importance of macropore continuity and tortuosity on preferential transport increased with an increase in solute retardation. General guidelines for simplifying continuity and tortuosity for modeling solute transport are presented for various initial and boundary conditions.
The use of organo-mineral fertilisers (OMFs) in agriculture is expected to increase in large part... more The use of organo-mineral fertilisers (OMFs) in agriculture is expected to increase in large part due to their advantages over mineral fertilisers and organic additives. However, the physical properties of pig slurry-based OMF required for storage, handling, and mechanical blending are still unknown. The objectives of this study were to determine the OMF physical properties in relation to 1) increasing the proportion of pig slurry compost and 2) changing the source of compost in the mixture. Twenty four mixtures of differing proportion of compost, monoammonium phosphate (MAP), and diammonium phosphate (DAP) were granulated. Increasing the compost proportion affected most OMF physical properties by increasing granule porosity, water content, and hygroscopicity and by decreasing the mean granule weight diameter, granule density, and crushing strength. Low-iron composts weakened the physical resistance of OMF in relation to storage whereas differences in OM content were not major factors affecting OMF physical properties. Increasing compost proportion increased water sorption from porous media, which might be beneficial for OMF field application. It is envisaged that this study could help commercial companies develop their own optimum OMF mixtures. However, determining the optimum compost proportion in OMF may depend on many other factors such as mineral fertiliser prices, compost availability, and crop response.
Some granulated organo‐mineral fertilizers (OMF) are made with peat and their utilization is expe... more Some granulated organo‐mineral fertilizers (OMF) are made with peat and their utilization is expected to increase mostly because of their advantages over mineral fertilizers. However, peat is a non‐renewable resource and could be replaced by sustainable organic materials such as stabilized composted pig slurry. The objectives of this study were to determine the changes of OMF physical properties when 1) substituting peat by composted pig slurry mixtures, 2) changing source of composted mixtures, and 3) increasing the level of organic material in the OMF. Thirty‐four mixtures of compost, monoamonium phosphate (MAP), diammonium phosphate (DAP), and peat were granulated in OMF at different proportions. The increase of the compost proportion and the decrease of organic material input (30% vs. 60% of organic materials) improved most physical properties of OMF granule such as bulk and granule densities, total and granular porosities, water content, abrasion fragility, crushing strength, critical relative humidity, and water sorption from moist porous media. In addition, most compost types resulted in similar physical properties of OMF granules. Finding the appropriate organic matter content requires more research and the optimum OMF mixture should be chosen as a function of its combined physical, chemical, and plant response properties.
The physical properties of organo-mineral fertilizers (OMF) are poorly understood, but must be me... more The physical properties of organo-mineral fertilizers (OMF) are poorly understood, but must be measured because they affect OMF transport, storage, handling, and soil behaviour. The aim of this study was to determine the relationships among physico chemical properties so that the number of measurements required by the industry during manufacturing is reduced. Organo-mineral fertilizers were granulated into 50 mixtures of composts, peat, and mineral fertilizers. Fifteen physical properties and 12 chemical properties were measured following standard and modified methods. Bulk density, easy and inexpensive to measure, significantly affected other physical properties (R20.74), such as tapped and granule densities and porosities, and crushing strength. In addition, concentrations of Fe, Mg, organic matter, and Na significantly affected many physical properties of OMF granules, whereas other chemical properties had a limited effect. These findings will directly affect OMF manufacturing by reducing time and costs needed for property measurements related to product development and quality control.
Propargyl bromide (3-bromopropyne, 3BP) is a potential alternative for methyl bromide. Little inf... more Propargyl bromide (3-bromopropyne, 3BP) is a potential alternative for methyl bromide. Little information is available about its efficiency in controlling pests. The purpose of this paper is to estimate the 3BP dose required for killing three pests and to compare the efficiency of watermanagement approaches to that of fumigation. The pests, Fusarium oxysporum Schlecht (fungus), Echinochloa crus-galli (L) Beauv (grass) and Tylenchulus semipenetrans Cobb (nematode) were exposed to different 3BP concentrations in a sandy loam at 30 ◦C in a closed system. The lethal dose for killing 90% of the population (LD90) was calculated from the total applied mass, and varied from 0.3 μgg−1 soil for the nematode, 3 μgg−1 for the grass, and 9 μgg−1 for the fungus. The concentration–time index for killing 90% of the population (CT90) was 11 μgg−1 h for the nematode, 112 μgg−1 h for the grass and 345 μgg−1 h for the fungus. 3BP seems as efficient as other fumigant alternatives in controlling these pests. Using an open system, it was shown that the volume of soil in which the pests were controlled varied for different irrigation managements. Even 96 h after fumigation (with a concentration 10 times higher than would potentially be applied in the field), more than 20% of the soil volume had not reached the fungus and grass CT90 of the non-irrigated soil. The soil underneath the furrow and the bed reached CT90 only slowly in all irrigated treatments even though techniques for increasing efficiency were used (tarping, surface sealing with water and high application rate).
The physical properties of organic-based fertilisers are not well known. The main objective of th... more The physical properties of organic-based fertilisers are not well known. The main objective of this study was to evaluate the range of granule size distributions of organic-based fertilisers and compare five approaches used to describe their size distribution: (1) the size guide number NSG and uniformity index; (2) the size range variation coefficient; (3) the uniformity coefficient; (4) the geometric standard deviation of the particle size diameter; and (5) the Rosin–Rammler function. Six mineral (MF), four bulk-blended organic-based (BOF), and ten compound organic-based fertilisers (COF) were studied. Standard NSG boxes and Tyler sieves were used to measure their granule size distribution. The size guide number ranged from 200 to 246 for MF, from 204 to 216 for BOF and from 99 to 255 for COF. The uniformity index was higher for slow release MF and for COF with NSG>210. All five distribution parameters separated the fertilisers into similar groups. The coefficient of uniformity was the least discriminating approach in grouping the fertilisers, while the geometric standard deviation and size range variation provided similar results and the Rosin–Rammler approach was the most discriminating. The NSG and uniformity index were estimated with the Rosin–Rammler function. Comparisons between estimated and measured size guide numbers indicated that the Rosin–Rammler function performs better for MF and for spherical granule shapes. Differences between the uniformity index values were greater for BOF, COF, and for cylindrical-shaped granules. The Rosin–Rammler function was not accurate for homogeneous and binomial particle size distributions, or for cylindrical granule shapes. However, in all other cases, this function was more precise and presented many advantages over the other methods, including the fact that it covers the entire range of particle sizes and can be used to estimate other parameters.
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Papers by Suzanne Allaire
was designed to estimate the level of risk of P contamination in water and how the level of risk has changed over 25 yr
(19812006) in agricultural watersheds of Canada. IROWC_P allows for a qualitative assessment of this risk in
comparison with other regions of eastern and western Canada, and the identification of high to very high risk watersheds
may require on-site assessment and the development of remedial action plans. This study presents an in-depth analysis of
IROWC_P results in the major Great Lakes watersheds of Canada. The risk of water contamination by P remains
acceptable (very low to moderate) in most Great Lakes watersheds, but better management practices (e.g., reduced
fertilization and manure application rates) and improved control of surface runoff may be required in watersheds which
are at increased risk. The Canadian watersheds of the Great Lakes basin showed a 39% reduction in their P applications in
excess of crop requirements between 1981 and 2006 bringing the Ontario provincial P-balance close to equilibrium in 2006.
Vulnerable areas were found south of Kitchener in the Lower Grand River watershed and east of Lake Simcoe.
from soils to water bodies. The objectives of this study were to develop methodologies for predicting
the likelihood of FF and LF occurrence in agricultural soils across Canada at the landscape scale, and to 29
use them as input parameters for risk indicators of water contamination. Both FF and LF consider the vol-
ume of infiltrating water. FF considers soil texture, layering, and content in coarse fragments, while LF
considers restricting layers, trees, slope, and soil depth. High risk of LF in British Columbia is associated
to shallow soils over compacted till in steep areas with higher density of trees. South of the St. Lawrence
River shows the largest region at high risk of LF due to much water infiltration, compacted till and shal
low soils. Eastern provinces have higher risk of FF, due to layered sandy soils and abundant precipitations.
LF and FF distribution maps can also be used as simple tools for supporting the identification of land sur
faces where management should consider subsurface contaminant transport processes and to warn
potential water pollution from inland agricultural contaminants.
was designed to estimate the level of risk of P contamination in water and how the level of risk has changed over 25 yr
(19812006) in agricultural watersheds of Canada. IROWC_P allows for a qualitative assessment of this risk in
comparison with other regions of eastern and western Canada, and the identification of high to very high risk watersheds
may require on-site assessment and the development of remedial action plans. This study presents an in-depth analysis of
IROWC_P results in the major Great Lakes watersheds of Canada. The risk of water contamination by P remains
acceptable (very low to moderate) in most Great Lakes watersheds, but better management practices (e.g., reduced
fertilization and manure application rates) and improved control of surface runoff may be required in watersheds which
are at increased risk. The Canadian watersheds of the Great Lakes basin showed a 39% reduction in their P applications in
excess of crop requirements between 1981 and 2006 bringing the Ontario provincial P-balance close to equilibrium in 2006.
Vulnerable areas were found south of Kitchener in the Lower Grand River watershed and east of Lake Simcoe.
from soils to water bodies. The objectives of this study were to develop methodologies for predicting
the likelihood of FF and LF occurrence in agricultural soils across Canada at the landscape scale, and to 29
use them as input parameters for risk indicators of water contamination. Both FF and LF consider the vol-
ume of infiltrating water. FF considers soil texture, layering, and content in coarse fragments, while LF
considers restricting layers, trees, slope, and soil depth. High risk of LF in British Columbia is associated
to shallow soils over compacted till in steep areas with higher density of trees. South of the St. Lawrence
River shows the largest region at high risk of LF due to much water infiltration, compacted till and shal
low soils. Eastern provinces have higher risk of FF, due to layered sandy soils and abundant precipitations.
LF and FF distribution maps can also be used as simple tools for supporting the identification of land sur
faces where management should consider subsurface contaminant transport processes and to warn
potential water pollution from inland agricultural contaminants.