Best management practices in northern agriculture : a twelve-year rotation and soil tillage study in Saguenay–Lac-Saint-Jean

In the northern agroecosystem of Saguenay–Lac-Saint-Jean, cash crops such as barley, canola, and field pea are gaining popularity over traditional perennial crops like alfalfa. However, very little information is available on the relatively long-term effect of different crop rotations and soil tillage practices on crop yields and soil quality parameters. This study was conducted at the Normandin Research Farm of Agriculture and Agri-Food Canada. Five rotation types [1: Canola–Barley–Barley–Pea (C–B–B–P); 2: Canola–Pea–Barley–Barley (C–P–B–B); 3: Canola–Barley–Pea–Barley (C–B–P–B); 4: Pea monoculture; and 5: Barley monoculture] and two soil tillage practices [1: Chisel plough (CP) and 2: Moldboard plough (MP)] were evaluated. Canola monoculture of was not included. The study began in 1999 on a former alfalfa field and ended in 2010 after three four-year rotation cycles. Barley monoculture decreased yields by 600 kg ha−1 in the last five years, whereas field pea monoculture decreased yields by about 1000 kg ha−1 in most years. Barley monoculture did not significantly reduce grain yields compared to C–B–B–P and C–P–B–B, highlighting the importance of alternate crops every year. Soil tillage (CP versus MP) did not significantly affect yields for all crops in most years; and when it did have an effect, it showed inconsistencies by either increasing or decreasing grain yields. Soil tillage also had insignificant impact regardless of the rotation type involved. Rotation type and soil tillage had insignificant effect on soil organic matter content, whereas CP increased nitrate and phosphorus content in the 0–20 cm soil layer. Rotation type had insignificant impact on soil physical properties, whereas CP improved soil water conductivity by 0.03 cm h−1 for C–B–B–P and barley monoculture. Compared to MP, CP improved soil macro-aggregate (2–6 mm) stability to water as well as aggregate mean weight diameter by about 15% for most of the rotations

Rotation des cultures annuelles et travail du sol en climat nordique : quelle combinaison semble la plus profitable au Saguenay-Lac-Saint-Jean?

Au Saguenay‒Lac-Saint-Jean, les cultures annuelles prennent de plus en plus d’ampleur au détriment des cultures pérennes. Toutefois, il y a peu d’information régionale sur les effets à long terme des pratiques culturales sur les rendements et les paramètres de la qualité des sols. L’objectif de cette étude a donc été de déterminer les effets des rotations des cultures annuelles et du travail du sol sur les rendements et les propriétés chimiques et physiques du sol. Trouver une combinaison de rotation et de travail du sol profitable dans le contexte nordique du Saguenay‒Lac-Saint-Jean est particulièrement important pour les producteurs de grandes cultures de la région

Assessment of spatio-temporal patterns of black spruce bud phenology across Quebec based on MODIS-NDVI time series and field observations

Satellite remote sensing is a widely accessible tool to investigate the spatiotemporal variations in the bud phenology of evergreen species, which show limited seasonal changes in canopy greenness. However, there is a need for precise and compatible data to compare remote sensing time series with field observations. In this study, fortnightly MODIS-NDVI was fitted using double-logistic functions and calibrated using ordinal logit models with the sequential phases of bud phenology collected during 2015, 2017 and 2018 in a black spruce stand. Bud break and bud set were spatialized for the period 2009–2018 across 5000 stands in Quebec, Canada. The first phase of bud break and the last phase of bud set were observed in the field in mid-May and at the beginning of September, when NDVI was 80.5% and 92.2% of its maximum amplitude, respectively. The NDVI rate of change was estimated at 0.07 in spring and 0.04 in autumn. When spatialized on the black spruce stands, bud break was detected earlier in the southwestern regions (April–May), and later in the northeastern regions (mid to end of June). No clear trend was observed for bud set, with different patterns being detected among the years. Overall, the process bud break and bud set lasted 51 and 87 days, respectively. Our results demonstrate the potential of satellite remote sensing for providing reliable timings of bud phenological events using calibrated NDVI time series on wide regions that are remote or with limited access

Lowbush blueberry fruit yield and growth response to inorganic and organic N-fertilization when competing with two common weed species

Inorganic N fertilizers are commonly used in commercial blueberry fields; however, this form of N can favor increased weed species’ growth, which can ultimately reduce the benefits of fertilization. We hypothesized that chipped ramial wood (CRW) compost is an effective alternative organic fertilizer for blueberry plants when weeds are present, as ericaceous shrub species are generally more efficient in utilizing organic N than herbaceous weed species. In this study, we measured the growth, fruit yield, and foliar N response of lowbush blueberry (Vaccinium angustifolium Aiton) to an application of 45 kg N ha-1 in the form of organic (CRW) or inorganic N (ammonium sulfate) in two areas of a commercial field colonized by either poverty oat grass (Danthonia spicata (L.) Beauv.) or sweet fern (Comptonia peregrina (L.) Coult.). We also assessed the impact of the fertilization treatments on litter decomposition rates. Contrary to our hypothesis, we found no significant increase in blueberry fruit yield or growth using CRW. By contrast, inorganic N-fertilization increased fruit yield by 70%. The effect was higher in the area colonized by D. spicata (+83%) than by C. peregrina (+45%). Blueberry fruit yield was on average twice higher in the area of the field having D. spicata than C. peregrina, suggesting a stronger competition with the latter. However, the increase in D. spicata density from 0–1 to >25 plants m-2 reduced fruit production by three-fold and strongly impacted vegetative growth in both fertilized and unfertilized plots. The impact of increased C. peregrina density was comparatively much lower, especially on vegetative growth, which was much higher in the area having C. peregrina. These patterns are likely due to a lower competition for N uptake with C. peregrina as this species can derive N from the atmosphere. Interestingly, the higher fruit yield in the area colonized by D. spicata occurred even in plots where the weeds were nearly absent (density of 0–1 plant m-2), revealing the influence of unidentified variables on blueberry fruit yield. We hypothesized that this difference resulted from over-optimal foliar N concentrations in the area colonized by C. peregrina as suggested by the significantly higher foliar N concentrations and by the negative correlation between foliar N concentrations and fruit yields in this area. The possibility of an influence of C. peregrina on flowering and pollination success, as well as of unidentified local site conditions is discussed. The tested N-fertilization treatments did not affect foliar N concentrations or litter decomposition rates. Overall, our results show that ammonium sulfate is very effective at increasing fruit yields but that both fruit yields and the efficiency of the N-fertilization treatment are decreased by increased D. spicata density, especially above 25 plants m-2. Although CRW did not significantly enhance fruit yields in the short term, this fertilizer may have a long-term beneficial effect

Spatial dependency and independency of nitrogen in lowbush blueberry commercial fields

Rhizomes of wild lowbush blueberry (Vaccinium angustifolium Aiton) extend horizontally, creating spatial dependency when fertilization trials are performed. Knowing this spatial dependency would help researchers to better design field studies. Here, we used labelled nitrogen (N) fertilizer (15N-(NH4)2SO4) to measure N translocation among blueberry stems for one old (56 year) and one younger (15 year) commercial field. Leaf 15N concentrations at the tip-dieback stage were used to monitor N acquisition. No difference between sites suggests no field age effect on N translocation. Spatial dependency and independency were reached for distances of ≤0.75 and ≥1.75 m from the fertilizer application point, respectively

How management practices influence vegetative and reproductive plant traits of wild lowbush blueberry species

Abstract: Optimizing agricultural practices is an effective way to increase fruit productivity in commercial wild lowbush blueberry (Vaccinium angustifolium Aiton; Vaccinium myrtilloides Michx) fields, but results from northern Quebec (Canada) are scarce. In this study, we assessed the effect of the main crop management practices, namely pruning method (mechanical and thermal), fungicide (with and without), and fertilization (mineral, organic, and without) on key vegetative and reproductive plant traits of both wild blueberry species. The experiment was conducted from fall 2016 to fall 2018, when the combination of pruning, fungicide, and fertilizing was applied. Results show that fertilizer application was the main management practice affecting vegetative and reproductive plant traits followed by fungicide application effects during pruning years only. Mineral fertilizer improved plant traits to a greater extent than organic fertilizer during the pruning phase only, and no significant differences in the second year after application (harvesting phase) suggest a delayed but similar final effect of organic fertilizer. Results also showed that V. myrtilloides produces taller stems with more leaves compared to V. angustifolium, whereas V. angustifolium produces more flower buds, a key reproductive plant trait. Results also highlight the fact that V. angustifolium needs both fertilizer and fungicide to keep leaves on the stem during late summer, whereas V. myrtilloides needs either fertilizers or fungicides. This study also shows that pruning method has no significant effect on any of the measured plant traits. However, we believe that long-term studies are still needed to assess the impact of pruning method over time. Résumé: Optimiser les pratiques agricoles est une bonne façon d’accroître le rendement fruitier des bleuetières commerciales de bleuet à feuilles étroites (Vaccinium angustifolium Aiton, Vaccinium myrtilloides Michx). Malheureusement, on possède peu de résultats qui l’illustrent dans le nord du Québec (Canada). Les auteurs ont évalué les effets des principales pratiques en usage sur les principaux caractères végétatifs et reproductifs des deux espèces, en l’occurrence l’élagage (mécanique et thermique), l’application (ou pas) d’un fongicide et celle d’un engrais (minéral, organique, aucun). L’expérience s’est déroulée de l’automne 2016 à l’automne 2018, période durant laquelle les auteurs ont combiné l’élagage à l’application du fongicide et de l’engrais. Selon les résultats obtenus, l’usage d’un engrais est la pratique qui affecte le plus les caractères végétatifs et reproductifs de la plante, suivie par l’application d’un fongicide, mais uniquement les années où il y a élagage. L’engrais minéral accentue plus les caractères de la plante que l’engrais organique, mais seulement lors de l’élagage. Si on ajoute à cela le fait qu’on ne relève aucun écart significatif l’année suivant celle de l’amendement (année de la récolte), on présume que l’engrais organique agit de façon identique, mais à retardement. V. myrtilloides a des tiges plus hautes portant plus de feuilles que V. angustifolium, espèce qui produit plus de bourgeons floraux, un caractère important pour la reproduction. Les résultats obtenus indiquent aussi que V. angustifolium a besoin d’un engrais et d’un fongicide pour que les feuilles restent attachées à leur tige à la fin de l’été, alors que V. myrtilloides n’a besoin que de l’un ou de l’autre. Par ailleurs, l’étude indique que la technique d’élagage n’a aucun effet sensible sur les autres caractères de la plante. Quoi qu’il en soit, les auteurs estiment qu’il faudrait entreprendre des recherches de plus longue haleine afin de mieux évaluer l’impact de l’élagage dans le temps

Limited effect of thermal pruning on wild blueberry crop and its root-associated microbiota

Thermal pruning was a common pruning method in the past but has progressively been replaced by mechanical pruning for economic reasons. Both practices are known to enhance and maintain high yields; however, thermal pruning was documented to have an additional sanitation effect by reducing weeds and fungal diseases outbreaks. Nevertheless, there is no clear consensus on the optimal fire intensity required to observe these outcomes. Furthermore, fire is known to alter the soil microbiome as it impacts the soil organic layer and chemistry. Thus far, no study has investigated into the effect of thermal pruning intensity on the wild blueberry microbiome in agricultural settings. This project aimed to document the effects of four gradual thermal pruning intensities on the wild blueberry performance, weeds, diseases, as well as the rhizosphere fungal and bacterial communities. A field trial was conducted using a block design where agronomic variables were documented throughout the 2-year growing period. MiSeq amplicon sequencing was used to determine the diversity as well as the structure of the bacterial and fungal communities. Overall, yield, fruit ripeness, and several other agronomical variables were not significantly impacted by the burning treatments. Soil phosphorus was the only parameter with a significant albeit temporary change (1 month after thermal pruning) for soil chemistry. Our results also showed that bacterial and fungal communities did not significantly change between burning treatments. The fungal community was dominated by ericoid mycorrhizal fungi, while the bacterial community was mainly composed of Acidobacteriales, Isosphaerales, Frankiales, and Rhizobiales. However, burning at high intensities temporarily reduced Septoria leaf spot disease in the season following thermal pruning. According to our study, thermal pruning has a limited short-term influence on the wild blueberry ecosystem but may have a potential impact on pests (notably Septoria infection), which should be explored in future studies to determine the burning frequency necessary to control this disease

Canadian goldenrod residues and extracts inhibit the growth of Streptomyces scabiei, the causal agent of potato common scab

Common scab is one of the most important diseases affecting potato crops worldwide. Using fresh residues and/or bio-products of Canadian goldenrod (Solidago canadensis) may offer an alternative to harmful conventional fumigants. In this study, we aimed to: (i) conduct a preliminary investigation of the utilization of S. canadensis to reduce common scab severity (Experiment 1), and (ii) determine the allopathic potentials of S. canadensis extracts on Streptomyces scabiei (also known as S. scabies), the most important soil pathogen responsible for causing common scab in North America (Experiment 2). Compared with control plants, preliminary results showed that adding 1.2 kg of fresh S. canadensis residue per m2 reduced scab severity by about 45% (Experiment 1). Furthermore, hexane and dichloromethane extracts of S. canadensis, at a concentration of 200 µg·mL−1, inhibited the growth of S. scabiei by about 97% (Experiment 2). These results were comparable with those using tetracycline (2.5 µg·mL−1), a known inhibitor of S. scabiei. Both experiments suggested that S. canadensis may represent a new approach for controlling potato common scab. More studies are required to better understand the mechanisms involved in S. canadensis induced reduction of common scab in order to standardize the approaches. La gale commune est une maladie tellurique importante chez la pomme de terre et l’utilisation de résidus et/ou extraits de verge d’or du Canada (Solidago canadensis) pourrait représenter une alternative prometteuse aux pesticides (fumigants) utilisés pour combattre la maladie. Les objectifs de cette recherche étaient i) effectuer une expérience préliminaire afin de mesurer les effets de l’incorporation de résidus frais de S. canadensis sur la sévérité de la gale commune (expérience 1) et ii) déterminer les potentiels allélopathiques des extraits de S. canadensis sur Streptomyces scabiei, un important agent pathogène causant la maladie de la gale commune (expérience 2). Nos résultats préliminaires issus de l’expérience 1 montrent qu’ajouter 1.2 kg m−2 de S. canadensis (résidus frais) permet de réduire significativement de 45% la sévérité de la gale commune. Les extraits de S. canadensis effectués avec l’hexane et le dichlorométhane et à des concentrations de 200 µg mL−1 permettent d’inhiber à 97% la croissance de S. scabiei, résultats comparables à la tétracycline (2.5 µg mL−1), un antibiotique connu pour inhiber la croissance de S. scabiei. Les résultats de cette étude montrent clairement et pour une première fois le potentiel d’utilisation de S. canadensis comme moyen de lutte contre la maladie de la gale commune chez la pomme de terre. D’autres recherche seront toutefois nécessaires pour bien comprendre et cibler les mécanismes impliqués afin de standardiser et d’optimiser cette nouvelle et prometteuse approche

Conditioning machine learning models to adjust lowbush blueberry crop management to the local agroecosystem

Agroecosystem conditions limit the productivity of lowbush blueberry. Our objectives were to investigate the effects on berry yield of agroecosystem and crop management variables, then to develop a recommendation system to adjust nutrient and soil management of lowbush blueberry to given local meteorological conditions. We collected 1504 observations from N-P-K fertilizer trials conducted in Quebec, Canada. The data set, that comprised soil, tissue, and meteorological data, was processed by Bayesian mixed models, machine learning, compositional data analysis, and Markov chains. Our investigative statistical models showed that meteorological indices had the greatest impact on yield. High mean temperature at flower bud opening and after fruit maturation, and total precipitation at flowering stage showed positive effects. Low mean temperature and low total precipitation before bud opening, at flowering, and by fruit maturity, as well as number of freezing days (<−5 °C) before flower bud opening, showed negative effects. Soil and tissue tests, and N-P-K fertilization showed smaller effects. Gaussian processes predicted yields from historical weather data, soil test, fertilizer dosage, and tissue test with a root-mean-square-error of 1447 kg ha−1. An in-house Markov chain algorithm optimized yields modelled by Gaussian processes from tissue test, soil test, and fertilizer dosage as conditioned to specified historical meteorological features, potentially increasing yield by a median factor of 1.5. Machine learning, compositional data analysis, and Markov chains allowed customizing nutrient management of lowbush blueberry at local scale

Nine years of in situ soil warming and topography impact the temperature sensitivity and basal respiration rate of the forest floor in a Canadian boreal forest

The forest floor of boreal forest stores large amounts of organic C that may react to a warming climate and increased N deposition. It is therefore crucial to assess the impact of these factors on the temperature sensitivity of this C pool to help predict future soil CO2 emissions from boreal forest soils to the atmosphere. In this study, soil warming (+2–4°C) and canopy N addition (CNA; +0.30–0.35 kg·N·ha-1·yr-1) were replicated along a topographic gradient (upper, back and lower slope) in a boreal forest in Quebec, Canada. After nine years of treatment, the forest floor was collected in each plot, and its organic C composition was characterized through solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Forest floor samples were incubated at four temperatures (16, 24, 32 and 40°C) and respiration rates (RR) measured to assess the temperature sensitivity of forest floor RR (Q10 = e10k) and basal RR (B). Both soil warming and CNA had no significant effect on forest floor chemistry (e.g., C, N, Ca and Mg content, amount of soil organic matter, pH, chemical functional groups). The NMR analyses did not show evidence of significant changes in the forest floor organic C quality. Nonetheless, a significant effect of soil warming on both the Q10 of RR and B was observed. On average, B was 72% lower and Q10 45% higher in the warmed, versus the control plots. This result implies that forest floor respiration will more strongly react to changes in soil temperature in a future warmer climate. CNA had no significant effect on the measured soil and respiration parameters, and no interaction effects with warming. In contrast, slope position had a significant effect on forest floor organic C quality. Upper slope plots had higher soil alkyl C:O-alkyl C ratios and lower B values than those in the lower slope, across all different treatments. This result likely resulted from a relative decrease in the labile C fraction in the upper slope, characterized by lower moisture levels. Our results point towards higher temperature sensitivity of RR under warmer conditions, accompanied by an overall down-regulation of RR at low temperatures (lower B). Since soil C quantity and quality were unaffected by the nine years of warming, the observed patterns could result from microbial adaptations to warming