Onions are highly responsive to endomycorrhizae and improved plant growth is among the benefits associated with this symbiosis, particularly in low phosphorus soils. Although this crop is grown extensively in organic soils, few studies have been conducted on these. Onion plants (Allium cepa L. cv. Norstar) were inoculated with Glomus aggregatum Schenck & Smith, Glomus clarum Nicolson & Schenck, Glomus fasciculatum Gerdemann & Trappe, Glomus intraradix Schenck & Smith and Glomus versiforme (Karst.) Berch and grown in the field and under controlled conditions to evaluate their efficiency in newly reclaimed organic soil of low P fertility. Three species were selected to evaluate the effects of introduced endomycorrhizal fungi effects and P fertilization (equivalent to 0, 24 and 48 kg P ha$ sp{-1}$) on the growth and mineral nutrition of onion plants. / Introducing endomycorrhizal fungi in non-sterile soil did not affect the growth and mineral nutrition of onion. Crop maturity was advanced when plants were inoculated, however. Increasing levels of P fertilization did not depress root colonization and onion growth was increased significantly at the highest rate only. These results suggest that higher levels than recommended could be used in this soil. Inoculation in $ gamma$-irradiated (10 kGy, $ sp{60}$Co) soil alleviated excessive Mn absorption by onion plants. Adding P fertilizer depressed growth and root colonization when plants were inoculated with G. clarum and G. intraradix and was related to the low irradiance levels used in this study. G. versiforme appeared to be the most efficient of the introduced species.

Field and laboratory studies were performed to estimate fluxes of the a-ace gases nitrogen monoxide (NO), nitrous oxide (N2O), and methane (CH4) in an organic soil, to determine the microbial processes involved, and to assess how soil water and nitrogen controlled flux rates. Metabolic inhibitors showed microbial nitrification to be the major NO source, regardless of the soil moisture content. Nitrification also produced N 2O, but denitrification losses of this gas from flooded, anaerobic soil were much higher. Up to 26% of nitrified N was converted to NO, but most of this (95%) was consumed microbially before it could escape across the soil surface. The NO-consuming process appeared to be co-oxidation by soil heterotrophs, not coupled to energy production. Organic matter content and CO2 production were therefore good predictors of NO oxidation rates across soil types, and NO oxidation was stimulated by manure addition. / Soil water and nitrogen had nonlinear effects on trace gas fluxes, acting on both production and consumption. Kinetic analysis showed that nitrate was a weak noncompetitive inhibitor, but ammonium a strong competitive inhibitor of soil CH4 oxidation at field fertilization rates. However, spatial and temporal factors complicated fertilization effects on CH4 oxidation in situ. Ammonium was immobilized in surface soil and rapidly nitrified, limiting its inhibitory effect on CH 4 oxidation. Fertilizer N stimulated nitrification and denitrification and therefore gaseous N-oxide production, but other, unexpected fertilizer effects were also observed. Ammonium fertilizer decreased NO oxidation rates. Nitrate and other salts stimulated NO and N2O losses during nitrification, an effect apparently related to soil nitrite accumulation. / The controls exerted on trace gas fluxes by soil water were mediated primarily through diffusion rates. Oxygen diffusion controlled the balance of anaerobic (methanogenesis and denitrification) versus aerobic (CH 4 oxidation and nitrification) processes. Soil moisture content also controlled the diffusion rate of atmospheric CH4 to soil methanotrophs, and the escape of gaseous N-oxides from production sites across the soil surface.

Following the Chernobyl accident in 1986, a range of countermeasures has been developed to reduce the transfer of 137Cs from soil to plant and from the plant into grazing animals. One such countermeasure is the application of potassium to the soil. However, little is known of any side-effects such an application may have on the ecosystem, the longevity of the application and the effectiveness in a range of soil types. An application of potash (KCl) was made to four organic upland soils in Cumbria. England at two application rates of 100 and 200 kg K ha-1 in June 1997 and at a single site in June 1998. Following application. a range of parameters within the ecosystem were recorded, through the collection of monthly samples of sail, vegetation and water samples over a period of fifteen months. The results indicate that the application was effective for at least one year following application, that a lag phase existed between potash application and any effect within each ecosystem and that the duration of this phase was site specific. The results also showed that the countermeasure was effective at all sites and there was little apparent difference between the two application rates. The parameters measured which included soil pH, plant biomass, changes in Cu, K, Mg, Mn and Ca concentrations within the soil and vegetation indicated only a relatively small effect of the application on the ecosystem as a whole. The application can be considered as a viable option for reducing the transfer of 137Cs from soil to plant. The study also shows that the effectiveness of the application is dependent on the measurement used. i.e. concentration ratios, Tag values or a total flux approach. It is argued that the flux approach is the most appropriate basis for comparing the effectiveness of potash as a countermeasure between several sites.

No description available.

No description available.

The focus of this study is on the use of bioremediation, as the primary method of decontamination for a soil contaminated with industrial waste oils. The area from which the samples were taken was used as a disposal site for oily wastewater for a period of more than 20 years. During this time the soil became severely contaminated. The site is approximately 1 acre in area and consists of three distinct soil strata: a solidified petroleum layer, a peat layer and a layer of muck and mud. This soil is approximately 96% organic matter. The purpose of this study is to determine if: given these site characteristics, is bioremediation a feasible option. Three phases were conducted to determine the usefulness of bioremediation in this situation. Phase one focused on the removal of total petroleum hydrocarbons (TPH) through nutrient addition and aeration. Phase two focused on quantifying and characterizing the reductions observed in phase one. Phase three again focused on quantifying and characterizing the reductions observed in phase one. The three phases of the study provided strong evidence that bioremediation was occurring in the soil and therefore, would be a viable means of remediation for a site with similar characteristics.

Cette étude a permis d'évaluer les quantités d'azote et de phosphore potentiellement minéralisables dans 34 sols organiques cultivés du Sud-Ouest du Québec. Les sols ont libéré en moyenne de 380 kg N ha-1 an-1 et moins de 2 kg P ha-1 an?1. Ils ont été classés en deux groupes de minéralisation. Un seuil critique de minéralisation de 0,8 mg N kg-1 j-1 correspondant à une teneur en carbone de 372 g kg-1 et à un rapport C/N maximal de 30 classait les sols avec un taux de succès de 85 %. Un seuil de minéralisation de 0,04 mg P kg-1 j.-1 correspondant à une teneur en carbone critique de 425 g C kg-1 classait les sols avec un taux de succès de 94 %. En serre, des plants de ray-grass prélevaient jusqu'à 3 fois plus d'azote sur certains sols très minéralisateurs que sur des sols pauvres. La richesse en phosphore des sols a conduit à une absence de réponse à la fertilisation.

Les sols organiques cultivés des basses-terres du Saint-Laurent sont parmi les sols maraîchers les plus productifs de la province et fournissent les aliments de base d'une grande partie de la population québécoise et du nord-est des États-Unis. Par leur mise en culture, ces sols sont exposés à différents processus de dégradation et de perte de hauteur de sol. Par conséquent, un important plan de conservation vise les sols dégradés et ceux à risque. Ce mémoire a pour objectifs de faire un bilan des propriétés physiques, chimiques et pédologiques de cinq tourbières de la région en plus de définir et de former des groupes de gestion des sols à des fins de conservation. L'hypothèse de départ supposait l'existence de groupes de sols liés à la qualité agronomique ou au grand groupe pédologique de 120 sites échantillonnés en 2019. Au terme de l'étude, une MANOVA a permis de conclure que la profondeur cultivable était une propriété clé pouvant classifier les sites en fonction de leur dégradation. Les sols ayant une profondeur cultivable de moins de 60 cm montraient des comportements significativement différents, résultats supportés par 17 propriétés discriminantes entre les groupes. Un second seuil pratique de 100 cm, celui-ci étant relié au drainage, a aussi été retenu. Ensuite, un second volet axé sur la cartographie numérique a permis de générer des cartes prédictives à l'échelle régionale de la profondeur au sol minéral, de l'épaisseur de la couche de coprogène et de la profondeur de sol cultivable en combinant les deux premières. Les données cumulées permettront de suivre l'évolution des sols dans le temps, alors que les cartes serviront d'outils complémentaires d'aide à la décision afin de cibler des zones d'intervention prioritaires pour conserver les ressources en sol de la région. / Organic soils converted to agricultural fields in the southwest plain of Montreal are amongst the most productive soils for horticulture in Quebec, not only supplying food for the province but also to the north-eastern part of the United-States. After their initial drainage to allow agriculture, Organic soils are susceptible to many forms of degradation and soil loss. Therefore, an important soil conservation plan is targeting degraded soils and soil at risk. The objectives of this master's thesis are to characterize soil physical, chemical and pedological properties of five peatlands in addition to forming soil conservation management groups. The initial hypothesis supposed the existence of latent groups related to soil quality or pedological Great Groups of 120 sampling sites visited in 2019. As a result of that work, a MANOVA lead to the conclusion that the peat maximum thickness of cultivation is a key property that is related to soil degradation. Soils with a peat maximum thickness of cultivation lower than 60 cm showed significantly more degradation signs. These results are supported by 17 discriminant properties between the groups. A second critical threshold of 100 cm was also established. The second part of this thesis used digital soil mapping as a tool to generate predictive maps at a regional scale of the depth to the mineral layer, coprogenous layer thickness and peat maximum thickness of cultivation by subtracting the first two maps. The rich dataset formed in this study will be used to monitor soil evolution while the maps will serve as complementary decision tools to target fields for a prioritized soil conservation intervention.

No description available.

Three drainage experiments were conducted on a newly developed organic soil where three cultural methods were superimposed. Measurements of carrot yields, subsidence, water table fluctuations, subsurface drain performance, hydraulic conductivity and soil bulk density were made. Rotovating the soil produced higher carrot yields than plowing or disking during the first year. The seven-year subsidence totalled 515 mm and depended mostly on organic soil depth. Hydraulic conductivity values did not change after five years of drainage. Bulk density of the top 0.20 m increased by 71% in 6 years, whereas the values down the profile increased between 3.3 and 16.2%. / The effect of two water table depths (WTD), 0.6 and 0.9 m, in an organic soil on soil water tension, subsidence swelling and carrot yields was studied in undisturbed cores in the greenhouse. Carrot yields were reduced by the 0.9 m WTD. Subsidence with the 0.9 m WTD was more than double that of the 0.6 m WTD. Raising the water table near the surface caused the soil to swell. / Hydraulic conductivity, bulk density, fiber content and drainable porosity were measured in undisturbed organic soil profiles. Values from all four properties decreased with increasing depth.