. 2003. Seeding rate, herbicide timing and competitive hybrids contribute to integrated weed management in canola (Brassica napus). Can. J. Plant Sci. 83: [433][434][435][436][437][438][439][440]. Implementing a favourable agronomic practice often enhances canola production. Combining several optimal practices may further increase production, and, given greater crop health and competitiveness, could also improve weed control. A field experiment was conducted at Lacombe and Lethbridge, Alberta, from 1998 to 2000, to determine the optimal combination of glufosinate-tolerant cultivar (hybrid InVigor 2153 or open-pollinated Exceed), crop seeding rate (100, 150, or 200 seeds m -2 ) and time of weed removal (two-, four-, or six-leaf stage of canola) for canola yield and weed suppression. At equal targeted seeding rates, the hybrid cultivar had greater seedling density (8 plants m -2 higher) and seed yield (22% higher) when compared with the openpollinated cultivar. Combining the better cultivar with the highest seeding rate, and the earliest time of weed removal led to a 41% yield increase compared with the combination of the weaker cultivar, the lowest seeding rate and the latest time of weed removal. The same optimal factor levels also favoured higher levels of weed control and lower weed biomass variability. Managing these factors at optimal levels may help increase net returns, reduce herbicide dependence and favour the adoption of more integrated weed management systems. cultivar tolérant au glufosinate (l'hybride InVigor 2153 ou la variété à pollinisation libre Exceed), la densité des semis (100, 150 ou 200 graines par mètre carré) et le moment du désherbage (stade de la deuxième, de la quatrième ou de la sixième feuille du canola) pour le rendement du canola et la suppression des mauvaises herbes. À la même densité des semis, le cultivar hybride donne un peuplement plus dense (8 plants de plus par mètre carré) et un meilleur rendement grainier (22 % de plus) que le cultivar à pollinisation libre. Quand on combine le meilleur cultivar à la plus forte densité de semis et à la première date de désherbage, le rendement augmente de 41 % comparativement à celui obtenu avec le cultivar le plus faible, la plus faible densité des semis et la dernière date de désherbage. Les facteurs optimaux favorisent aussi une lutte plus efficace contre les adventices et une moins grande variation de leur biomasse. La gestion de ces paramètres à leur niveau optimal pourrait entraîner de meilleurs revenus nets, réduire la dépendance aux herbicides et conduire à l'adoption de systèmes de lutte contre les mauvaises herbes mieux intégrés.

The nitrogen and non-nitrogen rotation benefits ofpea to succeeding crops. Can. J.plantSci.76:735-T45.Theinclusionofapulsecropinarotationoftenleadstogreaterseedyieldsinthesucceedingcereal crop. Two rotations were established at three sites in 1993 to examine the N and non-N rotation benefits of pea (Pisum satiwm L.) to the subsequent wheat (Triticum aestiwm L.) then oilseed crops. Wheat seed yield was 43oh greater (rotation benefit) when preceded by pearather than wheat, a consistent.oponr. among sites. Six to fourteen kg hrl of the extra 27 kghtt of N accumulated by wheat in the pea--wheat rotation was dirived from the additional N derived from pea residue' The additional soil N availability in the pea-wheat rotration, as indicated by the A-value, explained 8% ofthe rotation effect on seed yield (N benefit). The remaining 926/o of the yield advantage in the pea-wheat rotationwas attributed to non-N rotation benefit. The yield of the oilseed crop f6llowing the pea-wheat phise of the'rotation did not differ from that following the wheat-wheat phase. The influence of gro'wing conditions^and cropping history on the magnitude of the N to non-N rotation benefits, and the contribution of different non-N effects, should be investigated further.Key words: Rotation benefit, pea, wheat, residue N, non-N benefit The rotation benefit of a legume to the succeeding cereal kg ha-| . Typically, the C:N of pulse crop residues ranges crop is the yield advantage for the cereal relative to a cere-from 25:1 to 40: l, while the range of C:N for cereal residues al-cereal rotation. For example, seed yield of barley is 70:l to 100:1. The narrower C:N is believed to promote (Hordeumvulgarel.) (Evans et cereal crops (Bremer and Van Kessel 1992a; Jensen al. 1991). Wright (1990a) found that 100 kg ha-r of N fer-l994a,b). Therefore, the N contribution of pea to the suctilizer was required by barley following barley to produce a cgeding crop was much smaller than expected. Most of the yield comparable to unfertilized barley following pea.lsN that was not recovered by wheat was assimilated by the Evans et al. (1989) and Armstrong et al. (1994) showed microbes and consequently incorporated into a more passive that the N contribution of pea to the soil (N2 fxed in the fraction of the soil organic matter (Bremer and Van Kessel residue minus soil N accumulated in the seed) was about 20 1992b; Jensen 1994b

Typic Borolls) soil zones of the Canadian prairies (Gan and Noble, 2000). The area planted to lentil in Saskatch-Crops grown in previous years impact the amounts of residual soil ewan increased from 300 000 ha in 1995 to 670 000 ha water and nutrients available for subsequent plant growth. Appropriate sequences allow efficient use of the available soil resources by in (Anonymous, 2001. The inclusion of these crops the crop to increase yields at a system's level. This study was conducted as alternatives to cereals allows producers to become to determine whether the grain yield and grain crude protein concenless reliant on summer fallow and monoculture cropping tration (GCPC) of durum wheat (Triticum turgidum L.) were related systems. Expanded production of these alternative crops to crops grown in the previous 2 yr. Durum was grown following provides producers the opportunity to grow cereal crops pulses [chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.), on different types of stubble. The rotational benefits and dry pea (Pisum sativum L.)], oilseed [mustard (Brassica juncea derived from these opportunities are not well docu-L.) or canola (B. napus L.)], and spring wheat (Triticum aestivum L.) in southwest Saskatchewan from 1996 to 2000. Durum increased mented in this region. grain yields by 7% and GCPC by 11% when grown after pulse cropsTypes of crops grown in previous years may impact rather than after spring wheat. Durum after oilseeds increased grain the soils differently, affecting the amounts of residual yield by 5% and GCPC by 6%. Pulse and oilseed crops grown for soil water and nutrients available for subsequent plant the previous 2 yr increased durum grain yield 15% and GCPC 18% growth. Arranging crops in an appropriate sequence compared with continuous wheat systems. Fall residual soil NO 3 -N allows them to use the available resources more effiand available soil water accounted for 3 to 28% of the increased durum ciently and improves soil productivity at a system's level. yield in two of five site-years, whereas those two factors accounted for Zentner et al. (2001) reported that spring wheat GCPC 12 to 24% of the increased GCPC in three of five site-years. Durum grain yield was negatively related to GCPC. The relationship was

. 2004. Effect of nitrogen, seeding date and cultivar on oat quality and yield in the eastern Canadian prairies. Can. J. Plant Sci. 84: 1025-1036. The proportion of oat (Avena sativa L.) being used for race horses and human consumption has increased over the past 15 yr. The objective of this study was to evaluate the effects of N, seeding date and cultivar on grain yield components, grain yield and grain quality of oat under a directseeding system. Four N rates, three seeding dates and two cultivars were tested at Indian Head, Melfort, and Canora, SK, and Brandon, MB. Yield was more responsive to increasing N rates from 15 and 80 kg ha -1 when oat was seeded in early May versus early June. Panicles plant -1 was the yield component that accounted for most of the yield increase achieved from increasing rates of N, while kernel weight was the yield component that decreased as the rate of N increased. Physical seed quality decreased (plump seed decreased and thin seed increased) with delayed seeding and greater N fertilizer rates. Nitrogen fertilizer and seeding date had a much larger effect on the quality of CDC Pacer than AC Assiniboia. Combining early seeding, appropriate N fertility and well-adapted cultivars should increase the likelihood of optimizing oat yield and quality necessary for high-value markets. Depuis quinze ans, la quantité d'avoine (Avena sativa L.) employée pour nourrir les chevaux de course et pour la consommation humaine ne cesse d'augmenter. L'étude devait évaluer les effets de l'azote (N), de la date des semis et du cultivar sur les composantes du rendement grainier, le rendement grainier proprement dit et la qualité du grain de l'avoine ensemencée directement. Pour cela, les auteurs ont testé quatre taux d'application, trois dates de semis et deux cultivars à Indian Head, Melfort et Canora, en Saskatchewan, ainsi qu'à Brandon, au Manitoba. Le rendement réagit mieux à l'augmentation du taux d'application (de 15 à 80 kg de N par hectare) quand l'avoine est semée au début de mai plutôt qu'au début de juin. Le nombre de panicules par plant est la composante qui explique la majeure partie de la hausse de rendement dérivant de la plus grande quantité d'engrais utilisée; le poids de l'amande, en revanche, diminue avec la hausse du taux d'application. La qualité physique des semences diminue (réduction du nombre de grains ventrus et hausse du nombre de grains minces) quand on retarde la date des semis et accroît les applications d'engrais. L'engrais azoté et la date des semis influent plus sur la qualité de CDC Pacer que sur celle d'AC Assiniboia. En combinant de la bonne façon des semis précoces, le volume d'engrais et des cultivars bien acclimatés, on devrait se rapprocher du rendement optimal pour l'avoine et de la qualité souhaitée pour accéder aux marchés les plus lucratifs.

High costs of fertilizer in western Canada have generated interest in alternative N sources. Legumes produce N through fixation, and may increase soil residual and mineralizable N, thus reducing the need for fertilizer N in subsequent crops. Hybrid canola (Brassica napus L.) has a high N requirement for optimum yield, but knowledge of rotational effects of legumes on canola is limited. The objective was to determine the effects of legume and non-legume preceding crops on yield and quality of canola grown the following year and malting barley (Hordeum vulgare L.) grown after canola. Field pea (Pisum sativum L.), lentil (Lens culinaris Medik.), faba bean (Vicia faba L.), canola, and wheat (Triticum aestivum L.) harvested for grain, and faba bean grown as a green manure were direct-seeded at seven locations in 2009. Canola was seeded in 2010 and barley in 2011, with fertilizer N applied at 0, 30, 60, 90, and 120 kg ha -1 . On average, all legumes, except faba bean for seed, produced higher canola and barley yields than when wheat was the preceding crop. Faba bean green manure produced the highest yields, while canola on canola produced the lowest canola yield. The legumes had little negative effect on canola oil or barley protein concentration. Yields of both crops increased with increasing N rate, but canola oil concentration decreased, and barley protein increased. The results indicate that growing legumes for seed before hybrid canola can improve canola and subsequent barley yield without negatively affecting canola oil or malting barley protein.

A 3-yr study was conducted in Wheatland County, Alberta to determine if agronomic practices of growers influenced the occurrence of herbicide resistance in wild oat. Wild oat seeds were collected in 33 fields in 1997 and in 31 fields in each of 1998 and 1999 (one field per grower). Seedlings were screened for resistance to two acetyl-CoA carboxylase (ACCase) inhibitors, imazamethabenz, an acetolactate synthase (ALS) inhibitor, and triallate, a thiocarbamate herbicide. A questionnaire on herbicide resistance awareness and management practices was completed by each grower. Both ACCase and ALS inhibitor resistance in wild oat were linked to a lack of crop rotation diversity. In addition, ALS inhibitor–resistant wild oat was associated with conservation-tillage systems and recent use of herbicides with that mode of action. Results of this study suggest that timely tillage and inclusion of fall-seeded and perennial forage crops in rotations will effectively slow the selection of resistance in this grass species.

. 1996. Seeding rate and row spacing affect flax yields and weed interference. Can' J. Plant Sci. 76: 537_544. Seedin!rate and row spacing aie management practices that affect flax seed yield. Two experiments were conducted from lggg to 1990 to determine the influence offlix seeding rates (300, 600, and 900 seeds m-2) and row spacings (9, 18, and 27 cm). One was a flax-weed inrerference study (three-sites) and the other was a weed-free study (13 sites

The inclusion of a pulse crop in a rotation often leads to an increase in seed yield of the succeeding cereal crop. Landscape‐scale and small‐plot studies were established in 1993 to assess the N and non‐N rotation benefit by pea (Pisum sativum L.) to the subsequent wheat (Triticum aestivum L.) crop. In the second rotation phase, wheat seed yields were 982 kg ha−1 greater and total N accumulation increased by 46 kg ha−1 in the pea‐wheat rotation. Reduced leaf disease severity and grassy weed infestation were related to 91% of the yield advantage in the pea‐wheat rotation, the non‐N rotation benefit. A 129 N kg ha−1 increase in the A value (soil N supplying power) was related to 9% of the yield advantage in the pea‐wheat rotation, the N benefit. In both rotations, seed yield was about 400 kg ha−1 lower in the high‐catchment footslopes than the low‐catchment footslopes and shoulders. The landform effect on seed yield in the pea‐wheat rotation was related to greater soil water and N content in the high‐catchment footslopes. Increased grassy weed infestation in the high‐catchment areas of the wheat‐wheat rotation was related to lower seed yields in this same area. The rotation benefit of pea to wheat was 34% greater in the landscape‐scale vs. the small‐plot study. Topographic variation interacted with factors responsible for the non‐N rotation benefit. A landscape‐scale assessment of the rotation benefit from legumes can be used to develop site‐specific management strategies that consider the effect of crop rotation.