Two cultivars of carrot were sown in a sandy loam soil over two seasons with and without introduc... more Two cultivars of carrot were sown in a sandy loam soil over two seasons with and without introduction of commercial inoculum of Glomus intraradices or Glomus etunicatum, which was spread with an experimental sowing machine. VAM fungi effects on the yield and the quality of carrot varied from season to season. In 1997, both of the VAM fungi enhanced the average saleable yield of the two cultivars from 66.21 t/ha to 69.85 t/ha and 80.81 t/ha, respectively, for the treatment without the introduction of VAM fungi, G. etunicatum, and G. intraradices. The slight difference (5.03%) that occured between G. intraradices and the non-inoculated treatment, although not significant, represented 20.38% of the total percentage of rejected carrots. For the last season, the amount of rejected carrots was in the same range for all the treatments (13% to 14%). Nevertheless, both of the cultivars responded differently to mycorrhization. In both of the seasons, mycorrhizal colonization was high in all p...
The paper mills in Quebec produce approximately 330 000 Mg of raw de-inking paper sludges (RDS) p... more The paper mills in Quebec produce approximately 330 000 Mg of raw de-inking paper sludges (RDS) per year. These residues are rich in cellulose and lignin and may be used as soil conditioner. The effects of RDS on soil chemical properties, barley (Hordeum vulgare L. 'Chapais') growth, nutrient uptake and yields, and their residual effect on a subsequent strawberry (Fragaria × ananassa Duch. 'Kent') crop were investigated on a Tilly silt loam (Gleyed Humo-Ferric Podzol) from 1994 to 1996. Four rates of RDS (0, 15, 30 and 45 Mg ha−1) on a wet-weight basis were combined with four rates of supplemental N-mineral fertilizer (0, 45, 90 and 135 kg ha−1) as NH4NO3 The soluble inorganic N content of soil sampled 30 d after treatment application was significantly lower in plots treated with 45 Mg RDS ha−1 at all N rates. However, soluble inorganic N concentrations increased significantly with RDS rate to 20-cm depth in June 1995. The RDS application increased soil water content...
Common scab is a potato disease characterized by the formation of scab-like lesions on the surfac... more Common scab is a potato disease characterized by the formation of scab-like lesions on the surface of potato tubers. The actinobacterium Streptomyces scabiei is the main causal agent of common scab. During infection, this bacterium synthesizes the phytotoxin thaxtomin A which is essential for the production of disease symptoms. While thaxtomin A can activate an atypical programmed cell death in plant cell suspensions, it is possible to gradually habituate plant cells to thaxtomin A to provide resistance to lethal phytotoxin concentrations. Potato ‘Russet Burbank’ calli were habituated to thaxtomin A to regenerate the somaclone RB9 that produced tubers more resistant to common scab than those obtained from the original cultivar. Compared to the Russet Burbank cultivar, somaclone RB9 generated up to 22% more marketable tubers with an infected tuber area below the 5% threshold. Enhanced resistance was maintained over at least two years of cultivation in the field. However, average size...
The use of biological inputs in crop production systems, as complements to synthetic inputs, is g... more The use of biological inputs in crop production systems, as complements to synthetic inputs, is gaining popularity in the agricultural industry due to increasing consumer demand for more environmentally friendly agriculture. An approach to meeting this demand is the inoculation of field crops with beneficial microbes to promote plant growth and resistance to biotic and abiotic stresses. However, the scientific literature reports inconsistent results following applications of bio-inoculant to fields. The effects of inoculation with beneficial microbes on bulk soil and rhizospheric microbial communities is often overlooked as precise monitoring of soil microbial communities is difficult. The aim of this research was to use Illumina high throughput sequencing (HTS) to shed light on bulk soil and rhizospheric microbial community responses to two commercial microbial inoculants coated onto fertilizer granules, applied to potato fields. Bulk soil samples were collected 4 days before seedi...
Abstract Soil microorganisms play a key role in soil physical structure. Soil microbial community... more Abstract Soil microorganisms play a key role in soil physical structure. Soil microbial community structure and functions are in turn affected by soil aggregation or degradation. The objectives of this study were to determine the impact of (1) soil aggregate-size distribution and (2) soil compaction on bacterial community richness and structure under three intensive potato (Solanum tuberosum) cropping systems. In June and July 2014, soil samples were collected at a depth of 0-20 cm from 16 sites in Quebec, Canada. The samples were analyzed for aggregate-size distribution, particle-size distribution, total carbon, total nitrogen, total sulfur, oxalate-extractable potassium and phosphorus, gravimetric moisture content, pH and degree of compactness (DC). Soil bacterial community diversity was assessed by using the high-throughput sequencing Illumina MiSeq platform to target the V6-V8 region of bacterial 16S rRNA gene. Bacterial alpha diversity and community structure were found to be affected by cropping systems. Faith's phylogenetic diversity index and bacterial richness increased with increasing proportions of the 1–0.5 mm and 2–1 mm aggregate-size fractions and micro-aggregates in soils. Redundancy analysis revealed a strong correlation between soil bacterial community structure and soil aggregate-size distribution. Eight of the 27 dominant bacterial classes had a significant relationship with aggregate size fractions >2 mm, 1- 0.5 mm and
In a 338-d microcosm incubation experiment, greenhouse gas emissions (GHG) and bacterial diversit... more In a 338-d microcosm incubation experiment, greenhouse gas emissions (GHG) and bacterial diversity were studied in a clayey soil amended with 5% (w/w) biochar in the presence or absence of 4% (w/w) peat- and shrimp-based compost used as an additional C source. Two maple biochars produced at 400 °C (M400) or 700 °C (M700) and pine chips produced at 700 °C (P700) were tested. In comparison with soil supplemented or not with compost, the addition of any biochar resulted in lower total cumulative N2O emission (90% to 97%). The low porosity of M400 and M700 increased soil anaerobic conditions and resulted in higher total cumulative CH4 emission compared to the other soil treatments. In addition, the lowest total cumulative CO2 emission was observed with M700, probably due to its low-priming effect on native soil C decomposition. In all treatments, compost addition had the highest impact on both soil bacterial richness and community composition, particularly on bacteria of the class Anaerolineae. At day 338, results showed that modification of soil properties by maple biochars reduced bacterial diversity and induced shifts in the taxonomic composition of their community. In fact, heterotrophic bacteria involved in denitrification, such as genera Haliangium, Hyphomicrobium, Opititus, and Pedomicrobium, increased in abundance in response to the amendment with maple biochars. We conclude that the nature of biochar feedstock can impact soil bacterial diversity by changing soil physicochemical properties, thus influencing C dynamics, porosity, and pH, and by mitigating total cumulative GHG emissions.
Abstract We previously observed that the biochars used in this study can replace 15% (v/v) of per... more Abstract We previously observed that the biochars used in this study can replace 15% (v/v) of perlite in a peat-based growing medium (PBGM) without causing any harm to microbial biomass. However, little is known about their impacts on the plant-microbe-soil interactions and crop productivity. Thus, the aim of the present work was to evaluate in greenhouse trials, the effect of substituting perlite in PBGM by three types of biochar on tomato cv. Micro-Tom and sweet pepper cv. Redskin, growth and yield, on their water and fertilizer use efficiency and on the bacterial diversity found in PBGM. Biochars were derived from maple bark pyrolysed at 550 °C (M550) and 700 °C (M700) and from pine chips pyrolysed at 700 °C (P700). Tomato and sweet pepper plants were grown in a greenhouse and fertigated with mineral fertilizer at full or half of the recommended level. Compared to the control without biochar, adding 5, 10 or 15% (v/v) biochar improved plant water use efficiency and increased tomato and sweet pepper fruit dry weight yield respectively, by up to 32% and 54%. Biochar significantly increased N and P uptake efficiency, while reducing loss of NO3− and PO43− in leachates. In PBGM used to grow sweet pepper under full fertigation, the presence of 15% (v/v) M700 or P700 biochars significantly increased bacterial richness probably through the improvement of some ecological micro-niches such as C accessibility. This also allowed the establishment of potential plant growth promoting bacteria particularly Agrobacterium, Cellvibrio and Streptomyces, which showed a positive correlation with plant productivity and the chemical properties of PBGM. Our results suggest that the higher PBGM pH reached by adding 15% (v/v) biochar improved plant growth by increasing carbon, nitrogen and phosphorus availability and by favoring the establishment of plant beneficial bacteria. Therefore, substituting 15% (v/v) of perlite in PBGM with the three tested biochars appears to be a beneficial practice towards sustainable greenhouse production of tomato and sweet pepper, and this practice merit further investigation with other crops such as indeterminate cultivars.
Organic fertilization in greenhouses relies on organic fertilizers with low carbon/nitrogen ratio... more 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-week incubation experiment. Bacterial communities were characterized by sequencing the regions V6-V8 of the 16S rRNA gene on the high-throughput Illumina MiSeq platform, four weeks...
The decline of cultivated strawberry (Fragaria × ananassa Duchesne ex Rozier; Rosaceae) observed ... more The decline of cultivated strawberry (Fragaria × ananassa Duchesne ex Rozier; Rosaceae) observed in the province of Quebec, Canada, between 2012 and 2014 was mostly caused by persistent viruses: strawberry mild yellow edge virus (SMYEV) (Potexvirus; Alphaflexiviridae) and strawberry crinkle virus (SCV) (Cytorhabdovirus; Rhabdoviridae); and semi-persistent viruses: strawberry mottle virus (SmoV) (Secoviridae), strawberry vein banding virus (SVBV) (Caulimovirus; Caulimoviridae), and strawberry pallidosis virus (SPaV) (Crinivirus: Closteroviridae) transmitted by insect vectors. The objective of this study was to determine the sources of viral contamination in commercial strawberry fields in Quebec. Specifically, we wished to 1) determine the prevalence of persistent viruses in winged strawberry aphid Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae) specimens captured; 2) determine the prevalence of all viruses in wild strawberry Fragaria virginiana Miller plants near commerc...
Abstract Biochar production for soil amendment was recently proposed as a tool to mitigate climat... more Abstract Biochar production for soil amendment was recently proposed as a tool to mitigate climate change, reducing soil greenhouse gas (GHG) emissions and sequestrating carbon (C) in soil. The aim of this research project was to test the hypothesis that only biochars with specific requirements (low H/C org and O/C org ratios, high C/N ratio) can reduce soil N 2 O emissions without increasing CO 2 emissions in the short term. A 45-days incubation study was carried out, in which six engineered biochars made from the pyrolysis of wood, switchgrass and the solid fraction of pig manure (SFPM), were amended to two agricultural soils (loamy sand and silt loam) at a dose of 2% (w/w) in 1-liter jars. Soil moisture content was adjusted at 80% of water-filled pore space with a solution of ammonium nitrate that corresponds to 170 kg of nitrogen per hectare. N 2 O and CO 2 emissions were analysed on days 2, 3, and then weekly. Soil chemical properties and bacterial richness, composition and taxonomy were analysed after the incubation period. When compared to the control soils without biochar, N 2 O emissions were decreased by 42 to 90%, but only in the silt loam amended with biochars made from wood and switchgrass, these biochars having a high C/N ratio (>30). Lower N-NH 4 + and N-NO 3 − concentrations were observed in these biochar treatments than in control soil. Moreover, two bacterial classes ( Deltaproteobacteria and Thermoleophilia ) were correlated with a decrease in N 2 O emissions. For each type of biochar, those produced at the highest temperature with low O/C org and H/C org ratios resulted in the lowest increase in CO 2 emissions, which could indicate a higher biochar carbon stability. Overall, results of this study demonstrated that biochar can either increase or decrease soil GHG emissions depending on its properties, and that the effect can differ according to soil properties. Future long-term studies in the field in the presence of crop should be carried out in order to validate the conclusions of this study.
The identification of Lepidoptera larvae can be problematic when different species occur at the s... more The identification of Lepidoptera larvae can be problematic when different species occur at the same time in crops and when their identification requires dissection or laboratory rearing. In Quebec, this is the case for three Tortricidae that feed synchronously in apples: the codling moth [Cydia pomonella (L.)], the lesser appleworm [Grapholita prunivora (Walsh)] and the oriental fruit moth [Grapholita molesta (Busck)]. Codling moth larvae can usually be distinguished from the two other species by their larger size and the absence of anal comb, but larvae of the lesser appleworm and oriental fruit moth are nearly indistinguishable. The objective of our study is to validate DNA barcoding as a method for identifying major lepidopteran larval pest insects occurring in apple orchards in Quebec. This molecular method uses primers common to all Lepidoptera that target a 658 bp gene fragment coding for cytochrome oxydase I, which are specific to each lepidopteran species. 140 adult moths o...
Two cultivars of carrot were sown in a sandy loam soil over two seasons with and without introduc... more Two cultivars of carrot were sown in a sandy loam soil over two seasons with and without introduction of commercial inoculum of Glomus intraradices or Glomus etunicatum, which was spread with an experimental sowing machine. VAM fungi effects on the yield and the quality of carrot varied from season to season. In 1997, both of the VAM fungi enhanced the average saleable yield of the two cultivars from 66.21 t/ha to 69.85 t/ha and 80.81 t/ha, respectively, for the treatment without the introduction of VAM fungi, G. etunicatum, and G. intraradices. The slight difference (5.03%) that occured between G. intraradices and the non-inoculated treatment, although not significant, represented 20.38% of the total percentage of rejected carrots. For the last season, the amount of rejected carrots was in the same range for all the treatments (13% to 14%). Nevertheless, both of the cultivars responded differently to mycorrhization. In both of the seasons, mycorrhizal colonization was high in all p...
The paper mills in Quebec produce approximately 330 000 Mg of raw de-inking paper sludges (RDS) p... more The paper mills in Quebec produce approximately 330 000 Mg of raw de-inking paper sludges (RDS) per year. These residues are rich in cellulose and lignin and may be used as soil conditioner. The effects of RDS on soil chemical properties, barley (Hordeum vulgare L. 'Chapais') growth, nutrient uptake and yields, and their residual effect on a subsequent strawberry (Fragaria × ananassa Duch. 'Kent') crop were investigated on a Tilly silt loam (Gleyed Humo-Ferric Podzol) from 1994 to 1996. Four rates of RDS (0, 15, 30 and 45 Mg ha−1) on a wet-weight basis were combined with four rates of supplemental N-mineral fertilizer (0, 45, 90 and 135 kg ha−1) as NH4NO3 The soluble inorganic N content of soil sampled 30 d after treatment application was significantly lower in plots treated with 45 Mg RDS ha−1 at all N rates. However, soluble inorganic N concentrations increased significantly with RDS rate to 20-cm depth in June 1995. The RDS application increased soil water content...
Common scab is a potato disease characterized by the formation of scab-like lesions on the surfac... more Common scab is a potato disease characterized by the formation of scab-like lesions on the surface of potato tubers. The actinobacterium Streptomyces scabiei is the main causal agent of common scab. During infection, this bacterium synthesizes the phytotoxin thaxtomin A which is essential for the production of disease symptoms. While thaxtomin A can activate an atypical programmed cell death in plant cell suspensions, it is possible to gradually habituate plant cells to thaxtomin A to provide resistance to lethal phytotoxin concentrations. Potato ‘Russet Burbank’ calli were habituated to thaxtomin A to regenerate the somaclone RB9 that produced tubers more resistant to common scab than those obtained from the original cultivar. Compared to the Russet Burbank cultivar, somaclone RB9 generated up to 22% more marketable tubers with an infected tuber area below the 5% threshold. Enhanced resistance was maintained over at least two years of cultivation in the field. However, average size...
The use of biological inputs in crop production systems, as complements to synthetic inputs, is g... more The use of biological inputs in crop production systems, as complements to synthetic inputs, is gaining popularity in the agricultural industry due to increasing consumer demand for more environmentally friendly agriculture. An approach to meeting this demand is the inoculation of field crops with beneficial microbes to promote plant growth and resistance to biotic and abiotic stresses. However, the scientific literature reports inconsistent results following applications of bio-inoculant to fields. The effects of inoculation with beneficial microbes on bulk soil and rhizospheric microbial communities is often overlooked as precise monitoring of soil microbial communities is difficult. The aim of this research was to use Illumina high throughput sequencing (HTS) to shed light on bulk soil and rhizospheric microbial community responses to two commercial microbial inoculants coated onto fertilizer granules, applied to potato fields. Bulk soil samples were collected 4 days before seedi...
Abstract Soil microorganisms play a key role in soil physical structure. Soil microbial community... more Abstract Soil microorganisms play a key role in soil physical structure. Soil microbial community structure and functions are in turn affected by soil aggregation or degradation. The objectives of this study were to determine the impact of (1) soil aggregate-size distribution and (2) soil compaction on bacterial community richness and structure under three intensive potato (Solanum tuberosum) cropping systems. In June and July 2014, soil samples were collected at a depth of 0-20 cm from 16 sites in Quebec, Canada. The samples were analyzed for aggregate-size distribution, particle-size distribution, total carbon, total nitrogen, total sulfur, oxalate-extractable potassium and phosphorus, gravimetric moisture content, pH and degree of compactness (DC). Soil bacterial community diversity was assessed by using the high-throughput sequencing Illumina MiSeq platform to target the V6-V8 region of bacterial 16S rRNA gene. Bacterial alpha diversity and community structure were found to be affected by cropping systems. Faith's phylogenetic diversity index and bacterial richness increased with increasing proportions of the 1–0.5 mm and 2–1 mm aggregate-size fractions and micro-aggregates in soils. Redundancy analysis revealed a strong correlation between soil bacterial community structure and soil aggregate-size distribution. Eight of the 27 dominant bacterial classes had a significant relationship with aggregate size fractions >2 mm, 1- 0.5 mm and
In a 338-d microcosm incubation experiment, greenhouse gas emissions (GHG) and bacterial diversit... more In a 338-d microcosm incubation experiment, greenhouse gas emissions (GHG) and bacterial diversity were studied in a clayey soil amended with 5% (w/w) biochar in the presence or absence of 4% (w/w) peat- and shrimp-based compost used as an additional C source. Two maple biochars produced at 400 °C (M400) or 700 °C (M700) and pine chips produced at 700 °C (P700) were tested. In comparison with soil supplemented or not with compost, the addition of any biochar resulted in lower total cumulative N2O emission (90% to 97%). The low porosity of M400 and M700 increased soil anaerobic conditions and resulted in higher total cumulative CH4 emission compared to the other soil treatments. In addition, the lowest total cumulative CO2 emission was observed with M700, probably due to its low-priming effect on native soil C decomposition. In all treatments, compost addition had the highest impact on both soil bacterial richness and community composition, particularly on bacteria of the class Anaerolineae. At day 338, results showed that modification of soil properties by maple biochars reduced bacterial diversity and induced shifts in the taxonomic composition of their community. In fact, heterotrophic bacteria involved in denitrification, such as genera Haliangium, Hyphomicrobium, Opititus, and Pedomicrobium, increased in abundance in response to the amendment with maple biochars. We conclude that the nature of biochar feedstock can impact soil bacterial diversity by changing soil physicochemical properties, thus influencing C dynamics, porosity, and pH, and by mitigating total cumulative GHG emissions.
Abstract We previously observed that the biochars used in this study can replace 15% (v/v) of per... more Abstract We previously observed that the biochars used in this study can replace 15% (v/v) of perlite in a peat-based growing medium (PBGM) without causing any harm to microbial biomass. However, little is known about their impacts on the plant-microbe-soil interactions and crop productivity. Thus, the aim of the present work was to evaluate in greenhouse trials, the effect of substituting perlite in PBGM by three types of biochar on tomato cv. Micro-Tom and sweet pepper cv. Redskin, growth and yield, on their water and fertilizer use efficiency and on the bacterial diversity found in PBGM. Biochars were derived from maple bark pyrolysed at 550 °C (M550) and 700 °C (M700) and from pine chips pyrolysed at 700 °C (P700). Tomato and sweet pepper plants were grown in a greenhouse and fertigated with mineral fertilizer at full or half of the recommended level. Compared to the control without biochar, adding 5, 10 or 15% (v/v) biochar improved plant water use efficiency and increased tomato and sweet pepper fruit dry weight yield respectively, by up to 32% and 54%. Biochar significantly increased N and P uptake efficiency, while reducing loss of NO3− and PO43− in leachates. In PBGM used to grow sweet pepper under full fertigation, the presence of 15% (v/v) M700 or P700 biochars significantly increased bacterial richness probably through the improvement of some ecological micro-niches such as C accessibility. This also allowed the establishment of potential plant growth promoting bacteria particularly Agrobacterium, Cellvibrio and Streptomyces, which showed a positive correlation with plant productivity and the chemical properties of PBGM. Our results suggest that the higher PBGM pH reached by adding 15% (v/v) biochar improved plant growth by increasing carbon, nitrogen and phosphorus availability and by favoring the establishment of plant beneficial bacteria. Therefore, substituting 15% (v/v) of perlite in PBGM with the three tested biochars appears to be a beneficial practice towards sustainable greenhouse production of tomato and sweet pepper, and this practice merit further investigation with other crops such as indeterminate cultivars.
Organic fertilization in greenhouses relies on organic fertilizers with low carbon/nitrogen ratio... more 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-week incubation experiment. Bacterial communities were characterized by sequencing the regions V6-V8 of the 16S rRNA gene on the high-throughput Illumina MiSeq platform, four weeks...
The decline of cultivated strawberry (Fragaria × ananassa Duchesne ex Rozier; Rosaceae) observed ... more The decline of cultivated strawberry (Fragaria × ananassa Duchesne ex Rozier; Rosaceae) observed in the province of Quebec, Canada, between 2012 and 2014 was mostly caused by persistent viruses: strawberry mild yellow edge virus (SMYEV) (Potexvirus; Alphaflexiviridae) and strawberry crinkle virus (SCV) (Cytorhabdovirus; Rhabdoviridae); and semi-persistent viruses: strawberry mottle virus (SmoV) (Secoviridae), strawberry vein banding virus (SVBV) (Caulimovirus; Caulimoviridae), and strawberry pallidosis virus (SPaV) (Crinivirus: Closteroviridae) transmitted by insect vectors. The objective of this study was to determine the sources of viral contamination in commercial strawberry fields in Quebec. Specifically, we wished to 1) determine the prevalence of persistent viruses in winged strawberry aphid Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae) specimens captured; 2) determine the prevalence of all viruses in wild strawberry Fragaria virginiana Miller plants near commerc...
Abstract Biochar production for soil amendment was recently proposed as a tool to mitigate climat... more Abstract Biochar production for soil amendment was recently proposed as a tool to mitigate climate change, reducing soil greenhouse gas (GHG) emissions and sequestrating carbon (C) in soil. The aim of this research project was to test the hypothesis that only biochars with specific requirements (low H/C org and O/C org ratios, high C/N ratio) can reduce soil N 2 O emissions without increasing CO 2 emissions in the short term. A 45-days incubation study was carried out, in which six engineered biochars made from the pyrolysis of wood, switchgrass and the solid fraction of pig manure (SFPM), were amended to two agricultural soils (loamy sand and silt loam) at a dose of 2% (w/w) in 1-liter jars. Soil moisture content was adjusted at 80% of water-filled pore space with a solution of ammonium nitrate that corresponds to 170 kg of nitrogen per hectare. N 2 O and CO 2 emissions were analysed on days 2, 3, and then weekly. Soil chemical properties and bacterial richness, composition and taxonomy were analysed after the incubation period. When compared to the control soils without biochar, N 2 O emissions were decreased by 42 to 90%, but only in the silt loam amended with biochars made from wood and switchgrass, these biochars having a high C/N ratio (>30). Lower N-NH 4 + and N-NO 3 − concentrations were observed in these biochar treatments than in control soil. Moreover, two bacterial classes ( Deltaproteobacteria and Thermoleophilia ) were correlated with a decrease in N 2 O emissions. For each type of biochar, those produced at the highest temperature with low O/C org and H/C org ratios resulted in the lowest increase in CO 2 emissions, which could indicate a higher biochar carbon stability. Overall, results of this study demonstrated that biochar can either increase or decrease soil GHG emissions depending on its properties, and that the effect can differ according to soil properties. Future long-term studies in the field in the presence of crop should be carried out in order to validate the conclusions of this study.
The identification of Lepidoptera larvae can be problematic when different species occur at the s... more The identification of Lepidoptera larvae can be problematic when different species occur at the same time in crops and when their identification requires dissection or laboratory rearing. In Quebec, this is the case for three Tortricidae that feed synchronously in apples: the codling moth [Cydia pomonella (L.)], the lesser appleworm [Grapholita prunivora (Walsh)] and the oriental fruit moth [Grapholita molesta (Busck)]. Codling moth larvae can usually be distinguished from the two other species by their larger size and the absence of anal comb, but larvae of the lesser appleworm and oriental fruit moth are nearly indistinguishable. The objective of our study is to validate DNA barcoding as a method for identifying major lepidopteran larval pest insects occurring in apple orchards in Quebec. This molecular method uses primers common to all Lepidoptera that target a 658 bp gene fragment coding for cytochrome oxydase I, which are specific to each lepidopteran species. 140 adult moths o...
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Papers by Richard Hogue