Anne Vanasse

Nitrous Oxide Emissions Respond Differently to Mineral and Organic Nitrogen Sources in Contrasting Soil Types

The use of various animal manures for nitrogen (N) fertilization is often viewed as a viable replacement for mineral N fertilizers. However, the impacts of amendment type on NO production may vary. In this study, NO emissions were measured for 2 yr on two soil types with contrasting texture and carbon (C) content under a cool, humid climate. Treatments consisted of a no-N control, calcium ammonium nitrate, poultry manure, liquid cattle manure, or liquid swine manure. The N sources were surface applied and immediately incorporated at 90 kg N ha before seeding of spring wheat ( L.). Cumulative NO-N emissions from the silty clay ranged from 2.2 to 8.3 kg ha yr and were slightly lower in the control than in the fertilized plots ( = 0.067). The 2-yr mean NO emission factors ranged from 2.0 to 4.4% of added N, with no difference among N sources. Emissions of NO from the sandy loam soil ranged from 0.3 to 2.2 kg NO-N ha yr, with higher emissions with organic than mineral N sources ( = 0.015) and the greatest emissions with poultry manure ( < 0.001). The NO emission factor from plots amended with poultry manure was 1.8%, more than double that of the other treatments (0.3-0.9%), likely because of its high C content. On the silty clay, the yield-based NO emissions (g NO-N kg grain yield N) were similar between treatments, whereas on the sandy loam, they were greatest when amended with poultry manure. Our findings suggest that, compared with mineral N sources, manure application only increases soil NO flux in soils with low C content.

Extreme Grain-Based Cropping Systems: When Herbicide-Free Weed Management Meets Conservation Tillage in Northern Climates

Abstract The challenges associated with the adoption of conservation tillage and/or low-input cropping systems, whether organic or herbicide-free, across Canada are shaped by scale, environment, and local practices. A study in eastern Canada captured the challenges of introducing low-input cropping systems in mature (20+ yr) tillage treatments in a barley/red clover/corn/soybean rotation. Each mature tillage system came with its own weed problems, but this did not affect crops such as barley and red clover, which produced similar yields across high and low input systems. However, some form of primary tillage was needed to achieve adequate weed control and yield in organic (ORG) and herbicide-free (HF) systems. The HF and ORG systems with no-till actually failed to produce a corn crop but produced soybean yields that were half or less than that for other treatments. The successful combination of conservation tillage practices and low-input systems in eastern Canada would thus appear to be crop-specific, being easier to achieve in competitive cereal crops. In western Canadian organic agriculture, tillage is practiced with low-disturbance chisel plows instead of inversion plows. However, green manure crops (summer cover crops) are often terminated with tandem discs. Both roller crimpers and mowing can successfully kill annual green manure crops such as field pea and rye, and usually result in reduced weed growth following termination. However, the lack of tillage can result in lower crop yields in wheat following green manure terminated by roller crimping compared to tillage. Challenges for no-till organic practices include perennial weed control and soil fertility. Overall, flexible crop production programs such as the former Manitoba Pesticide Free Production program and the “Agriculture raisonnéeTM” program in Québec are more likely to promote sustained environmental, economic, and social prosperity than rigid adherence to organic or no-till practices. Nomenclature: Barley, Hordeum vulgare L.; corn, Zea mays L.; field pea, Pisum sativum L; red clover, Trifolium pratense L; rye, Secale cereale L; soybean, Glycine max (L.) Merr. Resumen Los retos asociados a la adopción de la labranza de conservación y/o los sistemas de cultivos de bajos insumos, ya sean orgánicos o libres de herbicidas, a lo largo de Canadá, están determinados por la escala, el ambiente y las prácticas locales. Un estudio en el este de Canadá capturó los retos de introducir sistemas de cultivos de bajos insumos en sistemas maduros de labranza (20+ años) en una rotación cebada/trébol rojo/maíz/soya. Cada sistema maduro de labranza tuvo sus propios problemas de malezas, pero esto no afectó a cultivos como cebada y trébol rojo, los cuales produjeron rendimientos similares en los sistemas de altos y bajos insumos. Sin embargo, algunas formas de labranza primaria fueron necesarias para alcanzar los controles de malezas y rendimientos adecuados en sistemas orgánicos (ORG) y libres de herbicidas (HF). Los sistemas HF y ORG con cero-labranza fallaron en producir cosechas de maíz, aunque produjeron rendimientos de soya que fueron la mitad o menos que aquellos producidos en otros tratamientos. La combinación exitosa de prácticas de labranza de conservación y sistemas de bajos insumos en el este de Canadá pareciera ser específica al cultivo, siendo más fácil de alcanzar con cultivos tales como cereales competitivos. En la agricultura orgánica del oeste de Canadá, la labranza se realiza con arados de cinceles de baja perturbación en lugar de usar arados de inversión. Sin embargo, los cultivos para abono verde (cultivos de cobertura de verano) son generalmente terminados con discos en tándem. Tanto rodillos de cuchillas y aplanadoras como chapeadoras pueden matar exitosamente cultivos anuales para abono verde, tales como leguminosas y centeno, lo que usualmente resulta en un crecimiento reducido de las malezas después de la terminación del cultivo. Sin embargo, la ausencia de labranza puede resultar en bajos rendimientos en trigo después de la terminación del cultivo para abono verde usando rodillos en comparación con la labranza. Los retos en las prácticas orgánicas de cero-labranza incluyen el control de malezas perennes y la fertilidad del suelo. En general, programas flexibles de producción tales como el anterior programa de Manitoba para la Producción Libre de Plaguicidas y el programa “Agriculture raisonnéeTM” en Québec tienen más probabilidades de promover en forma sostenida la prosperidad ambiental, económica y social que la adhesión rígida a prácticas orgánicas o de cero-labranza.

Floristic diversity, size, and vertical distribution of the weed seedbank in ridge and conventional tillage systems.

Abstract The floristic diversity and the vertical distribution of the weed seedbank were studied in ridge tillage (RT) and conventional tillage (CT) systems in clay and clay loam soils. Viable seedbank populations were monitored during 3 yr using germination in a greenhouse. Ridge-tilled fields had a larger soil seedbank (2,992 seeds m−2) than moldboard-plowed fields (1,481 seeds m−2) in the top 15 cm. This result can be explained by the larger perennial seedbank of RT fields at both the 0- to 5-cm and 5- to 15-cm depths. Annual dicot seeds were more abundant in clay soils than in clay loams at the two soil depths. Annual grass seeds were more abundant under CT than under RT in clay soils at the two sampled depths. In clay loams, the density of annual grass seeds in RT fields was six times greater than in CT fields in the top 5 cm of soil and two times greater at the 5- to 15-cm depth. The vertical distribution of total seeds in soil did not differ between tillage systems. The top 5 cm of the 15-cm soil core contained 35 and 46% of all weed seed in CT and RT systems, respectively. However, the CT system had the highest concentration of annual dicot seeds 5 to 15 cm deep, whereas in the RT system, the same depth contained the highest concentration of perennial seeds. These results confirm that tillage systems and soil types can regulate seedbanks. Weed management programs must take this information into account. Nomenclature:Dicamba; SAN 582, 2-chloro-N-[(1-methyl-2-methoxy)ethyl]-N-(2,4-dimethyl-thien-3-yl)-acetamide; glyphosate; Abutilon theophrasti Medik ABUTH, velvetleaf; Ambrosia artemisiifolia L. AMBEL, common ragweed; Chenopodium album L. CHEAL, common lambsquarters; Echinochloa crus-galli (L.) Beauv. ECHCG, barnyard grass; Oxalis stricta L. OXAST, yellow woodsorrel; Panicum dichotomiflorum (L.) Michx. var. geniculatum (Wood) Fern. PANDI, fall panicum; Plantago major L. PLAMA, broad-leaved plantain; Setaria faberi Herrm. SETFA, giant foxtail; Setaria pumila (Poir) Roem et Schult SETLU, yellow foxtail; Setaria viridis (L.) Beauv. SETVI, green foxtail; Taraxacum officinale Weber in Wiggers TAROF, dandelion; Brassica napus L., oilseed rape; Glycine max (L.) Merr., soybean; Triticum aestivum L., wheat; Zea mays L., corn.

Spatial processes structuring riparian plant communities in agroecosystems: implications for restoration

The disruption of hydrological connectivity by human activities such as flood regulation or land-use changes strongly impacts riparian plant communities. However, landscape-scale processes have generally been neglected in riparian restoration projects as opposed to local conditions, even though such processes might largely influence community recovery. We surveyed plant composition of field edges and riverbanks in 51 riparian zones restored by tree planting (565 1-m2 plots) within two agricultural watersheds in southeastern Québec, Canada. Once the effects of environmental variables (hydrology, soil, agriculture, landscape, restoration) were partialled out, three models of spatial autocorrelation based on Morans eigenvector maps and asymmetric eigenvector maps were compared to quantify the pathways and direction of the spatial processes structuring riparian communities. The ecological mechanisms underlying predominant spatial processes were then assessed by regression trees linking species response to spatial gradients to seed and morphological traits. The structure of riparian communities was predominantly related to unidirectional spatial gradients from upstream to downstream along watercourses, which contributed more to species composition than bidirectional gradients along watercourses or overland. Plant traits selected by regression trees explained 22% of species response to unidirectional upstream-downstream gradients in field edges and 24% in riverbanks, and predominantly corresponded to seed traits rather than morphological traits of the adult plants. Our study showed that even in agriculturally open landscapes, water flow remains a major force structuring spatially riparian plant communities by filtering species according to their seed traits, thereby suggesting long-distance dispersal as a predominant process. Preserving hydrological connectivity at the watershed-scale and restoring riparian plant communities from upstream to downstream should be encouraged to improve the ecological integrity of rivers running through agricultural landscapes.

Effect of Glyphosate on Fusarium Head Blight in Wheat and Barley Under Different Soil Tillages

Fusarium head blight (FHB) is a serious disease in the wet conditions of eastern Canada. Tillage practices and herbicide applications have been reported to influence disease intensity. This study aimed to determine the effect of glyphosate on FHB development in wheat and barley and on Fusarium graminearum inoculum production under different soil tillages. The experiment was performed during 2 years (2007 and 2008) at two different sites in Quebec, Canada. Six trials were set in both sites, combining two cereal species (wheat and barley) and three soil tillages: moldboard plow, spring tillage (minimum-till), and direct drilling. For each trial, glyphosate or other herbicides were applied on Roundup Ready soybean the year preceding cereal crops, constituting the main plots. The next year, three wheat and three barley cultivars were sown as subplots. FHB index, Fusarium-damaged kernels (FDK), deoxynivalenol (DON) content, and F. graminearum inoculum production were measured. Glyphosate had no significant effect on FHB index, FDK, or DON content, whatever the trial and the site. F. graminearum inoculum production was enhanced by glyphosate in only 1 of 12 trials. Cultivar effect was highly significant on DON content. The relationship between F. graminearum inoculum from soybean residues and DON content was weak.

Influence of arbuscular mycorrhizae on soil P dynamics, corn P-nutrition and growth in a ridge-tilled commercial field

Ridge-tilled corn (Zea mays L.) could benefit from arbuscular mycorrhizal (AM) fungi. Under low soil disturbance, AM hyphal networks are preserved and can contribute to corn nutrition. A 2-yr study was conducted in the St. Lawrence Lowlands (Quebec, Canada) to test the effects of indigenous AM fungi on corn P nutrition, growth, and soil P in field cropped for 8 yr under ridge-tillage. Phosphorus treatments (0, 17, 35 kg P ha-1) were applied to AM-inhibited (AMI) (fungicide treated) and AM non-inhibited (AMNI) plots. Plant tissue and soil were sampled 22, 48 and 72 days after seeding (DAS). P dynamics was monitored in situ with anionic exchange membranes (PAEM) from seeding to the end of July. AMNI plants showed extensive AM colonization at all P rates. At 22 DAS, AMI plants had decreased growth in the absence of P inputs, while AMNI plants had higher dry mass (DM) and P uptake in unfertilized plots. The PAEM was lower in the AMNI unfertilized soils in 1998 and at all P rates in 1999, indicating an inverse...

Seeding rate and cultivar effects on yield, yield components and grain quality of spring spelt in eastern Canada

Dorval, I., Vanasse, A., Pageau, D. and Dion, Y. 2015. Seeding rate and cultivar effects on yield, yield components and grain quality of spring spelt in eastern Canada. Can. J. Plant. Sci. 95: 841-849. There is currently an increasing demand from master millers for spelt (Triticum aestivum ssp. spelta), but little is known about crop management of spring spelt under the eastern Canadian climate in organic or low-input systems. Field experiments were carried out at three sites in Quebec from 2011 to 2013 to assess the effect of cultivar (CDC Origin, CDC Zorba, CDC Nexon, CDC Silex) and seeding rate (250, 300, 350, 400 and 450 grains m-2) on grain and straw yields, yield components and some grain quality characteristics of spelt. CDC Origin produced higher hulled grain yields at all sites, while CDC Silex produced similar hulled grain yields and achieved the highest naked grain yields at two of the three test sites. The hull content varied from 24.0 to 37.6% among cultivars. CDC Origin had the highest hull content at each site. The seeding rate generally had no effect on yields, but had an effect on yield components; increasing seeding rates slightly increased the number of spikes per square metre and decreased the number of grains per spike, while the 1000-grain weight remained unaffected. Protein content of all cultivars was high (14.2 to 15.4%), while falling number varied from 219 to 385 s.

DELTA: An Integrated Indicator-Based Self-Assessment Tool for the Evaluation of Dairy Farms Sustainability in Quebec, Canada

A self-assessment tool was developed for use by dairy farmers in Quebec and aims to measure the agri-environmental, techno-economic, and social dimensions of sustainability. Some of the methodological choices made in the development of the tool and its validation by the end users are presented. Validation of the tool was conducted with 17 farmers using a questionnaire divided into three sections regarding their perception of the application procedure, the consistency of the results in regards to the reality of their farm, and the utility of the tool. Analysis of the questionnaires confirms the relevance of the tool. Four case studies were used to examine the results in depth and clarify the relationships between the three components of sustainability of dairy farms and between these components and the indicators. Case studies results demonstrate that the aggregation of indicators into a single score could remove information necessary for the comprehension. The visual integration through radar diagrams leaves the flexibility for the farmer to understand his scores and compare himself to peers. Based on DELTA, a new schematization of a sustainable farm has emerged where a farmer makes compromises to manage sustainability on his farm and maintain the balance of the farm system.

Insecticides (dimethoate and lambda-cyhalothrin) for soybean aphid control - are they toxic to earthworms? Evidence from laboratory and field bioassays

Whalen, J. K., Benslim, H. and Vanasse, A. 2012. Insecticides (dimethoate and lambda-cyhalothrin) for soybean aphid control - are they toxic to earthworms? Evidence from laboratory and field bioassays. Can. J. Soil Sci. 92: 751-758. Outbreaks of the exotic soybean aphid (Aphis glycines Matsumura) cause significant yield loss of soybean [Glycine max (L.) Merr.] grown in North America. This study assessed the toxicity of dimethoate and lambda cyhalothrin, recommended to control soybean aphid, to earthworms, a non-target organism present in soybean fields. Laboratory bioassays showed the lethal and sub-lethal concentrations of dimethoate and lambda cyhalothrin to adult Eisenia fetida (Savigny) and their offspring. The most sensitive toxicity endpoint was adult E. fetida growth rates, which had a half maximal effective concentration (EC50) of 6.39 mg active ingredient (a.i.) kg-1 soil for dimethoate and 5.41 mg a.i. kg-1 soil for lambda cyhalothrin after 28 d exposure. The field bioassay was done on two commercial farms with naturally occurring earthworms (including Aporrectodea turgida, Allolobophora chlorotica, Aporrectodea rosea, Lumbricus terrestris and Eiseniella tetraedra). Soybean fields received insecticidal sprays during 2007 and 2008. Timely application of dimethoate (both farms) and lambda cyhalothrin (one farm) controlled the aphid outbreak in 2007 and increased soybean yield by 9 to 22% over the untreated control. These insecticide treatments had no effect on field earthworm populations, probably because application rates recommended to control soybean aphid were up to three orders of magnitude lower than the EC50 determined in laboratory tests. In conclusion, recommended application levels of dimethoate and lambda cyhalothrin for soybean aphid control are not toxic to earthworms in soybean fields.

Chemical and mechanical weed management strategies for grain pearl millet and forage pearl millet

There are limited options for controlling weeds in grain and forage pearl millet production in eastern Canada. Field studies were conducted near Quebec City in 2005 and 2006 to evaluate the effectiveness of herbicidal treatments (s-metolachlor/benoxacor and pendimethalin) and harrowing to control weeds and maximize yield in grain and forage pearl millet cultivation. s-Metolachlor/benoxacor and pendimethalin were applied either preemergence or early postemergence at the full dose recommended for corn and at half of that dose. Harrowing was evaluated at the three- and the five-leaf stage of pearl millet. In both types of pearl millet, s-metolachlor/benoxacor applied preemergence reduced plant density and yield. All other herbicidal treatments caused no visual injury to pearl millet and adequately controlled annual weeds, leading to grain and forage yields similar or slightly lower than those of the hand-weeded control. Better barnyard grass control resulted from early postemergence application of s-metolach...