Plusieurs études ont démontré l’importance de la fertilisation en azote (N) dans l’accroissement de la productivité du bleuet. Peu d’information est toutefois disponible sur le phosphore (P) et le potassium (K). Les objectifs de cette étude étaient de déterminer les impacts de la fertilisation NPK sur les propriétés chimiques du sol et les paramètres agronomiques. Les traitements ont consisté en quatre doses de N (0 à 90 kg N ha⁻¹), deux doses de P (0 et 20 kg P₂O₅ ha⁻¹) et quatre doses de K (0 à 90 kg K₂O ha⁻¹). Le dispositif expérimental, établi sur six sites au Saguenay-Lac-St-Jean, était un factoriel en blocs complets aléatoires. Le pH du sol a diminué suivant les applications de N, de 0,1 unité dans la couche de surface et de 0,2 unité dans la couche 5–30 cm. Des accumulations de P et de K ont été mesurées en surface. Les rendements en fruits ont augmenté de 43 % à la suite des applications de N. Une application de 20 kg P₂O₅ ha⁻¹ a semblé nécessaire pour maximiser les rendements lorsque les apports en N dépassaient 50 kg ha⁻¹. Une dose ≥ 30 kg K₂O ha⁻¹ a diminué les rendements en fruits jusqu’à 24 % lorsque combinée avec une dose > 60 kg N ha⁻¹.

Metal-contaminated soils present a great threat to natural ecosystems and human health. Remediation studies focusing on metal-polluted soils with high organic matter (OM > 20%) are limited. This study evaluated the effectiveness of biochar, compost, diammonium phosphate (DAP), and iron oxides (Fe-O), in immobilizing metals from an OM-rich boreal forest soil contaminated with arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). A laboratory incubation study was conducted with soil amended with biochar (5% w w⁻¹), compost (5% w w⁻¹), DAP (0.2% w w⁻¹), or Fe-O (0.2% w w⁻¹), and a control (without amendment) for 6 months at field capacity moisture content. Metal concentrations were determined in pore water collected at 0, 2, 4, and 6 months after incubation. Soil was extracted sequentially for metals after the incubation period. Metal concentrations in pore water were significantly reduced by different amendments as follows: As by biochar and Fe-O, Cd by biochar, compost, and DAP, Cu by biochar, Pb by compost and DAP, and Zn by biochar and compost. Sequential extractions revealed biochar and (or) compost transferred Cd, Cu, Pb, and Zn from the labile pool to the non-labile pool confirming their effectiveness as amendments for remediation of metal-contaminated OM-rich boreal forest soil.

Organic fertilization in greenhouses relies on organic fertilizers with low carbon/nitrogen ratio. Nitrogen (N) availability thus depends on an efficient mineralization driven by microbial communities. However, data on the mineralization rate of such fertilizers are scarce, and their improper use can lead to either N deficiency, or N losses to the environment. Consequently, better knowledge of N availability following organic fertilization is crucial for the development of sustainable greenhouse organic horticulture. We investigated the effect of pelleted poultry manure (PM) and blood (BM), feather (FM), alfalfa (AM), and shrimp (SM) meals on N availability and bacterial communities in a peat-based organic growing medium and a mineral soil. Nitrogen and carbon (C) pools were measured periodically over a 52 wk incubation experiment. Bacterial communities were characterized by sequencing the regions V6–V8 of the 16S rRNA gene on the high-throughput Illumina MiSeq platform, 4 wk after the start of the incubation. Nitrogen mineralization plateaued for the mineral soil and the peat substrate at, respectively, 41% and 63% of applied N for PM, 56%–93% (BM), 54%–81% (FM), 34%–53% (AM), and 57%–73% (SM). Organic fertilizers supported markedly contrasted bacterial communities, closely linked to soil biochemical properties, especially mineral N, pH, and soluble C. Alfalfa meal promoted the highest Shannon diversity index in the mineral soil, whereas SM and PM increased it in the peat-based growing medium. Our results quantified the mineralization and highlighted the impact on bacterial communities of commonly used organic N fertilizers in conditions relevant to organic greenhouse horticulture.

A novel laboratory method was developed to control soil freeze–thaw cycles and study the effects of freezing intensity on soil conditions and N₂O emissions. The method created unidirectional freeze–thaw (top-down), similar to field conditions. Soil was placed in boxes that were insulated on the sides, heated from the bottom, and left open on the top. Snow was placed on the soil surface, and the boxes were placed in separate climate-controlled chambers to freeze (−9 °C) and thaw (5 °C). The method was used in an experiment to evaluate the links between freezing degree days (FDD), soil water content, carbon (C) and nitrogen (N) transformations, and N₂O emissions. Results showed that N₂O emissions were greatest from soils that experienced more freezing, with the 185 FDD treatment emitting significantly more N₂O than the 50 FDD treatment (17.7 vs. 7.7 mg N₂O-N m⁻² d⁻¹). Peaks in soil water content during thaw preceded peaks in N₂O flux, but increasing water content by simulating rain (in addition to snow melt) did not increase N₂O emissions compared with snow melt alone. Extractable soil C and N increased in the top 5 cm when soils froze; however, greater emissions were not linked to greater C and N concentrations at individual points in time. Higher N₂O emissions at 134 and 185 FDD were associated with greater C exposure (i.e., extractable soil C concentration integrated over time) than the 50 FDD treatment.

To study the effects of mechanical compaction on soil macropore structure in the process of reclamation, this study investigated reclaimed soil mechanically compacted in coal mining area with high groundwater level. The computed tomography scanning technology was employed to get soil slice images, and ArcGIS^® was used to analyze the porosity, number, size, morphology, and distribution of macropores in reclaimed soil, at different compaction times (0, 1, 3, 5, 7, and 9) and depths (0–20, 20–40, and 40–60 cm). Our results proved that the mechanical compaction could decrease the macroporosity, number, and equivalent diameter (ED) of the macropores in reclaimed soil, while the morphology became rounded. The distribution of macropore ED was steeper and more asymmetrical than macropore circularity. However, mechanical compaction could make them flat and symmetrical. The macroporosity, number, ED, and circularity of macropores in packing layer (40–60 cm) were smaller than backfilling top layer (0–20 cm) and sublayer (20–40 cm). Thus, we suggest that subsoiling in packing layer is responsible for the improved macropore characteristics. Moreover, these macropores will possess better permeability if the compaction times are controlled.

Forest fires significantly change soil function and quality. Finding an effective way to accelerate the restoration of soil quality after forest fires is a major issue. This study investigated the soil quality index (SQI) during vegetation restoration after a fire in a Larix gmelinii plantation, throughout different restoration years. Fifteen physical, chemical, and biological properties of soil were examined using principal component analysis, and soil quality was assessed by SQI. The results revealed that soil physical properties, chemical properties, and enzyme activities showed the most improvement after 24 yr of restoration. Soil microbial biomass carbon content and microbial biomass nitrogen content increased with restoration years. Soil bulk density, microbial biomass nitrogen, sucrase, and catalase were retained in the minimum data set. After 24 yr of restoration, SQI was the highest, with a value of 0.52, followed by natural restoration, 21, 13, and 16 yr; the SQI after 3 yr of restoration was the lowest, with a value of 0.26. Artificial regeneration accelerated the recovery of soil quality after 24 yr. Soil quality should be monitored continuously in the study area.

Emission of ammonia from agriculture is a major concern. The analytical analysis of ammonia is known to have some challenges and might be causing systematic errors. The effect of absorbing acids on an ion selective electrode (ISE) and the Berthelot colouring reaction, in terms of precision, was quantified. We show that commonly used acid absorbents do not have a significant influence on the precision of the ISE, whereas the acids had significant influence on measurements using the Berthelot reaction. Using the ISE in low-volume eluates (3 mL) did not influence the precision compared with the recommended 100 mL.