• Authors:
    • Van Eerd, L. L.
    • Vyn, R. J.
    • Robinson, D. E.
    • O'Reilly, K. A.
  • Source: Weed Technology
  • Volume: 25
  • Issue: 3
  • Year: 2011
  • Summary: The effectiveness of cover crops as an alternative weed control strategy should be assessed as the demand for food and fiber grown under sustainable agricultural practices increases. This study assessed the effect of fall cover crops on weed populations in the fall and spring prior to sweet corn planting and during sweet corn growth. The experiment was a split-plot design in a pea cover-cover crop-sweet corn rotation with fall cover crop type as the main plot factor and presence or absence of weeds in the sweet corn as the split-plot factor. The cover crop treatments were a control with no cover crop (no-cover), oat, cereal rye (rye), oilseed radish (OSR), and oilseed radish with rye (OSR+rye). In the fall, at Ridgetown, weed biomass in the OSR treatments was 29 and 59 g m(-2) lower than in the no-cover and the cereal treatments, respectively. In the spring, OSR+rye and rye reduced weed biomass, density, and richness below the levels observed in the control at Bothwell. At Ridgetown in the spring, cover crops had no effect on weed populations. During the sweet corn season, weed populations and sweet corn yields were generally unaffected by the cover crops, provided OSR did not set viable seed. All cover crop treatments were as profitable as or more profitable than the no-cover treatment. At Bothwell profit margins were highest for oat at almost Can$600 ha(-1) higher than the no-cover treatment. At Ridgetown, compared with the no-cover treatment, OSR and OSR+rye profit margins were between Can$1,250 and Can$1,350 ha(-1) and between Can$682 and Can$835 ha(-1), respectively. Therefore, provided that OSR does not set viable seed, the cover crops tested are feasible and profitable options to include in sweet corn production and provide weed-suppression benefits.
  • Authors:
    • Gillard, C. L.
    • Sikkema, P. H.
    • Pynenburg, G. M.
  • Source: Crop Protection
  • Volume: 30
  • Issue: 3
  • Year: 2011
  • Summary: Two common production constraints of dry bean (Phaseolus vulgaris) in Ontario are annual weeds and anthracnose (caused by Colletotrichum lindemuthianum). Dry bean is not considered a competitive crop and weed interference can result in substantial yield losses, while anthracnose is considered one of the most devastating diseases in dry bean production. A study conducted in Ontario Canada, examined the effect of two herbicide programs on weed management, thiamethoxam insecticide treatment on plant enhancement and three fungicide programs on anthracnose development in a navy bean cv. 'OAC Rex'. The premium herbicide program (s-metolachlor + imazethapyr) reduced percent weed ground cover relative to the economic herbicide program (trifluralin) in five of six locations. Thiamethoxam increased emergence and vigour at only one location, which contradicts reported benefits of thiamethoxam on plant health. The herbicide or thiamethoxam treatments did not affect anthracnose disease severity, visible seed quality, net yield or economic return. The fungicide seed treatment was often superior to the untreated control, for a number of the parameters measured. The application date of the foliar fungicide, relative to the onset of disease, varied between site-years. This dramatically influenced the fungicide's effectiveness. Foliar fungicides increased seed quality and net economic return compared to the control when applied prior to disease development. The combination of fungicide seed treatment followed by a foliar fungicide provided the largest reduction in anthracnose severity. (c) 2010 Elsevier Ltd. All rights reserved.
  • Authors:
    • LaFond, G. P.
    • May, W. E.
    • Tenuta, M.
    • Entz, M. H.
    • Turmel, M. S.
  • Source: Canadian Journal of Plant Science
  • Volume: 91
  • Issue: 6
  • Year: 2011
  • Summary: Leguminous cover crops are becoming a popular way to increase the sustainability of agricultural systems. Previously, cover crops have been found to increase colonization by arbuscular mycorrhizal fungi (AM F) and phosphorus and micronutrient uptake. Long-term field studies were conducted to test the hypothesis that self-regenerating black medic (Medicago lupulina cv. George) cover crops increase AM F colonization and early nutrient uptake in flax (Linum usitatissimum). Field experiments were established in 2000 (Manitoba) and 2002 (Saskatchewan) using a flax wheat (Triticum aestivum) oat (Avena sativa) rotation. In a second experiment, intact soil cores were harvested from the plots in spring and tested for soil disturbance and cover crop effects under controlled environment conditions (CEC). Both seedling flax crops sampled from the field in 2005 and 2006 and flax growth in CEC showed high levels of AMF root colonization, but no significant influence of the cover crop on AM F colonization by arbuscules or hyphal structures was detected. The AMF enhancing practices used in the experiments (i.e., zero-tillage and inclusion of mycorrhizal crops) may have contributed to the lack of cover crop effect on AMF colonization. The cover crop had no effect on macro- or micronutrient uptake by flax except during drought conditions (Winnipeg 2006), where flax biomass was reduced by 38% and the total uptake of N, P, Zn and Cu was decreased by 34, 30, 31 and 35%, respectively, in the medic treatment.
  • Authors:
    • Holm, F. A.
    • Johnson, E. N.
    • Blackshaw, R. E.
    • O'Donovan, J. T.
    • Harker, K. N.
    • Clayton, G. W.
  • Source: Weed Science
  • Volume: 59
  • Issue: 3
  • Year: 2011
  • Summary: Growing crops that exhibit a high level of competition with weeds increases opportunities to practice integrated weed management and reduce herbicide inputs. The recent development and market dominance of hybrid canola cultivars provides an opportunity to reassess the relative competitive ability of canola cultivars with small-grain cereals. Direct-seeded (no-till) experiments were conducted at five western Canada locations from 2006 to 2008 to compare the competitive ability of canola cultivars vs. small-grain cereals. The relative competitive ability of the species and cultivars was determined by assessing monocot and dicot weed biomass at different times throughout the growing season as well as oat (simulated weed) seed production. Under most conditions, but especially under warm and relatively dry environments, barley cultivars had the greatest relative competitive ability. Rye and triticale were also highly competitive species under most environmental conditions. Canada Prairie Spring Red wheat and Canada Western Red Spring wheat cultivars usually were the least competitive cereal crops, but there were exceptions in some environments. Canola hybrids were more competitive than open-pollinated canola cultivars. More importantly, under cool, low growing degree day conditions, canola hybrids were as competitive as barley, especially with dicot weeds. Under most conditions, hybrid canola growers on the Canadian Prairies are well advised to avoid the additional selection pressure inherent with a second in-crop herbicide application. Combining competitive cultivars of any species with optimal agronomic practices that facilitate crop health will enhance cropping system sustainability and allow growers to extend the life of their valuable herbicide tools.
  • Authors:
    • Schoenau, G.
    • Tabil, L.
    • Adapa, P.
  • Source: Biomass and Bioenergy
  • Volume: 35
  • Issue: 1
  • Year: 2011
  • Summary: Grinding experiments were conducted on non-treated and steam exploded barley, canola, oat and wheat straw using a forage chopper and a hammer mill (screen sizes of 30, 6.4, 3.2 and 1.6 mm) to determine specific energy requirements, and geometric mean particle size and distribution of ground material. The bulk density of non-treated biomass was significantly higher than bulk density of steam exploded agricultural biomass. For non-treated agricultural straw, the particle density of canola and oat straw significantly increased with a decrease in hammer mill screen size from 30 to 1.6 mm. The particle density of steam exploded barley and oat straw was significantly higher than non-treated straw, except for barley at 6.4 mm hammer mill screen size. The particle density of steam exploded canola straw was not statistically different from non-treated straw. The chopper consumed highest (3.15 +/- 0.09 kWh t(-1)) and lowest (1.96 +/- 0.33 kWh t(-1)) specific energy to chop barley and canola straw, respectively. The highest and lowest specific energy was consumed by wheat (42.57 +/- 2.04 kWh t(-1)) at 1.6 mm and canola (1.46 +/- 0.30 kWh t(-1)) straws ground using 30 mm hammer mill screen size, respectively. For steam exploded agricultural biomass, the highest and lowest specific energy was consumed by oat (33.18 +/- 3.10 kWh t(-1)) at 1.6 mm and canola (2.69 +/- 0.26 kWh t(-1)) straws ground using 6.4 mm hammer mill screen size, respectively. Specific energy required by hammer mill to grind non-treated and steam exploded barley, canola, oat and wheat straw showed a negative power correlation with hammer mill screen sizes. (C) 2010 Elsevier Ltd. All rights reserved.
  • Authors:
    • Helgason, B. L.
    • Walley, F. L.
    • Germida, J. J.
  • Source: Applied Soil Ecology
  • Volume: 46
  • Issue: 3
  • Year: 2010
  • Summary: Aggregation is important for soil functioning, providing physical protection of organic matter and microbial inhabitants. Tillage disrupts aggregates, increases wind and water erosion of soils and exposes formerly protected organic matter to decomposition and losses. Microbial biomass and community dynamics in dry-sieved aggregate-size classes from long-term no-till (NT) and conventionally tilled (CT) soils were examined using phospholipid fatty acid analysis (PLFA). Bacterial, fungal, and total biomass were up to 32% greater in NT compared to CT aggregates. Aggregate size also affected microbial biomass, which was highest in the 1-2 mm size class. Arbuscular mycorrhizal fungi (AMF) were particularly affected by tillage disturbance with increases of 40-60% among aggregate-size classes in NT vs. CT, but glomalin related soil protein concentration was not different between tillage treatments or among aggregate-size classes. Bacterial stress biomarkers were higher in CT than NT aggregates but were not significantly correlated with total C, total N or C:N ratio, indicating that the physiological status of bacteria within aggregates was not simply governed by the quantity of available resources. Ordination analysis of PLFA profiles demonstrated a shift in microbial community structure between NT and CT aggregates, correlated with AMF abundance in NT aggregates and increased bacterial stress biomarkers in CT aggregates. Our results demonstrated greater microbial biomass and altered microbial community structure in NT vs. CT aggregates. This work demonstrates that tillage management influences microbial community structure within aggregates and may provide a potential explanation for differences in process rates observed in NT vs. CT soils. Further research into the processes that govern community structure in aggregates from NT and tilled soils is needed to better understand how the interaction of microorganisms with their physical environment affects nutrient turnover and availability.
  • Authors:
    • Molnar, L. J.
    • Blackshaw, R. E.
    • Moyer, J. R.
  • Source: Canadian Journal of Plant Science
  • Volume: 90
  • Issue: 4
  • Year: 2010
  • Summary: Farmers on the Canadian prairies are interested in including legume cover crops in their cropping systems to reduce fertilizer inputs and improve farm sustainability. A field study was conducted to determine the merits of establishing alfalfa ( Medicago sativa L.), red clover ( Trifolium pratense L.) or Austrian winter pea ( Pisum sativum L.) cover crops in fall or in spring with winter wheat ( Triticum aestivum L.). Spring-planted legumes emerged well within the winter wheat crop, but their growth was limited under these semi-arid conditions. Fall-planted red clover had low plant densities following winter in two of three experiments and fall-planted winter pea reduced winter wheat yield by 23 to 37% compared with the no cover crop control. In contrast, fall-planted alfalfa exhibited good winterhardiness, provided some weed suppression without reducing winter wheat yield, caused only a slight reduction in soil water content, and contributed an extra 18 to 20 kg ha -1 of available soil N at the time of seeding the following spring crop. Additionally, fall-planted alfalfa increased the yield of succeeding canola ( Brassica napus L.) in unfertilized plots in two of three experiments. Further research is warranted to better understand the agronomic and economic benefits of alfalfa-winter wheat intercrops under a wider range of environmental conditions.
  • Authors:
    • O'Donovan, J.
    • Harker, K.
    • Clayton, G.
    • Dosdall, L.
    • Hummel, J.
  • Source: Biological Control
  • Volume: 55
  • Issue: 3
  • Year: 2010
  • Summary: Several natural enemies regulate populations of root maggots ( Delia spp.) (Diptera: Anthomyiidae) in canola ( Brassica napus L.) in western Canada, among them the rove beetles Aleochara bilineata Gyllenhal and Aleochara verna Say (Coleoptera: Staphylinidae) and the hymenopteran Trybliographa rapae Westwood (Hymenoptera: Figitidae). Intercrops of canola and wheat ( Triticum aestivum L.) can be part of an integrated pest management strategy to reduce damage by Delia spp. to canola. We investigated several intercropping regimes of canola and wheat to determine effects on parasitism of Delia radicum (L.) and activity densities of adult A. bilineata and A. verna. Studies were conducted over four site-years in central Alberta, Canada in 2005 and 2006. Mean parasitism rates of D. radicum puparia by A. bilineata ranged from 7.27% to 81.69%. Increasing proportions of wheat in intercrops significantly reduced parasitism by A. bilineata in one site-year. Parasitism of D. radicum by T. rapae was not affected by intercropping; mean parasitism rates were between 2.17% and 14.55%. In one site-year combined parasitism by all parasitoids significantly increased with increasing canola as a proportion of total crop plant populations. Pitfall trap collections of adult A. bilineata increased with increasing proportions of canola in some site-years. Collections of A. verna adults were low relative to A. bilineata and were largely unaffected by intercropping. Although canola-wheat intercrops do not appear to favour parasitism of D. radicum, reductions in canola root damage by Delia larvae in intercrops, reported previously, suggest that canola-wheat intercrops may nevertheless be favourable as a crop protection strategy.
  • Authors:
    • Lajeunesse, J.
    • Pageau, D.
    • Fregeau-Reid, J.
    • Collin, J.
    • Vanasse, A.
    • Lanoie, N.
    • Durand, J.
  • Source: Canadian Journal of Plant Science
  • Volume: 90
  • Issue: 3
  • Year: 2010
  • Summary: Naked oat ( Avena sativa L.) harvested in the province of Quebec, Canada, develops on average 10% covered grains and sometimes more. The objective of this study was to determine the effect of soil type, herbicides and their application stages on the proportion of covered grains in naked oat genotypes. Three genotypes were evaluated over 2 yr at two experimental sites. At each site, trials were seeded on two different soil types and each entry was treated with one of three types of herbicides: bromoxynil/MCPA, dicamba/MCPA and thifensulfuron methyl/tribenuron methyl, and compared with a weed-free check. The herbicides were applied at Zadoks 12-13 and 22-23. Results showed that dicamba/MCPA herbicide, applied at Zadoks 12-13, increased covered grains compared with the weed-free check and more covered grains were produced with the application made at Zadoks 22-23. However, differences in genotype reactions were observed. Few differences were found among the other weed control treatments. The application of dicamba/MCPA at Zadoks 22-23 decreased yield and test weight, but increased kernel weight. The other weed control treatments had no effect on agronomic characteristics.
  • Authors:
    • Lajeunesse, J.
    • Pageau, D.
    • Reid, J. F.
    • Collin, J.
    • Vanasse, A.
    • Lanoie, N.
    • Durand, J.
  • Source: CROP SCIENCE
  • Volume: 50
  • Issue: 5
  • Year: 2010
  • Summary: Naked oat ( Avena sativa L.) grown in Quebec, Canada, produces an average of 10% covered grains. The objectives of this study were to evaluate the effects of environment, herbicide, and genotype on the proportion of covered grains, to study the relation between the presence of awns and the proportion of covered grains, and to determine the location of covered grains on the plant (tiller) and on the panicle. Eight oat lines were evaluated over 2 yr at four experimental sites. Each line was treated with bromoxynil/MCPA, dicamba/MCPA, or thifensulfuron methyl/tribenuron methyl applied at Zadoks 12-13 and compared to a hand-weeded check. The highest percentages of covered grains, 5.5 and 6.9%, were found at different sites in 2006 and 2007. The application of dicamba/MCPA increased the percentage of covered grains in the lines normally producing a higher proportion of covered grains, but low producing lines were less affected. Minor differences were found among the other weed control treatments. No relation was found between the presence of awns and the proportion of naked grains. Covered grains were mostly produced on the main stem and their position on the panicle depended on genotype and weed control treatment.