. 1999. Effect of barley plant density on wild oat interference, shoot biomass and seed yield under zero tillage. Can. J. Soil Sci. 79: 655-662. There has been little research aimed at developing regression models to describe the effects of barley and wild oat plant density on barley yield loss, or wild oat biomass and seed yield. Such models are an important component of integrated weed management systems, and can help determine when weed control with herbicides is economical. Field experiments were conducted over 4 yr at Vegreville, Alberta, to determine the interactive effects of wild oat and barley plant density on barley and wild oat variables in a zero tillage system. A nonlinear regression model in most cases provided good descriptions of barley yield loss, wild oat shoot dry weight, and wild oat seed yield as functions of wild oat and barley plant densities. The interactive effect of wild oat and barley plant density on percentage barley yield loss did not differ significantly (P = 0.05) among years. A pooled regression model describing barley yield loss accounted for 57% of the variation, and provides a means of estimating yield loss due to wild oat in barley grown under zero tillage. Barley yield loss increased as wild oat density increased but the magnitude of the yield loss diminished with increasing barley plant density. Wild oat economic threshold densities varied among years, and were strongly influenced by barley price and expected wild oatfree yield. Economic thresholds were greater at higher barley plant densities. Barley seed weight decreased with increasing barley plant density, and to a lesser extent with increasing wild oat density. The interactive effect of wild oat and barley plant density on wild oat seed yield varied significantly with year, and appeared to be influenced by climatic conditions. The cooler, wetter spring of 1996 favored wild oat seed production (by several orders of magnitude) compared with the relatively warmer and drier spring of 1995. Each year wild oat seed yield and shoot dry weight decreased as barley plant density increased. The results suggest that seeding barley at relatively high rates may reduce the need for wild oat control with herbicides in zero tillage systems.Key words: Zero tillage, wild oat interference, barley seeding rate, nonlinear regression O'Donovan, J. T., Newman, J. C., Harker, K. N., Blackshaw, R. E. et McAndrew, D. W. 1999. Effet de la densité de peuplement de l'orge sur l'importance de la concurrence exercée par la folle avoine, ainsi que sur la production végétative et semencière de la mauvaise herbe en régime de semis direct. Can. J. Plant Sci. 79: 655-662. Il n'y a eu jusqu'ici que peu de tentatives de modélisation par régression pour décrire les effets de la densité de peuplement de l'orge et de la folle avoine sur le manque à produire de l'orge ou sur le rendement en biomasse et en graines de la folle avoine. Ce type de modèle constitue pourtant une importante composante des systèmes de lutte intégrée contre les mauvaises herbes et il pe...

Field experiments were initiated at Alliance and Hairy Hill, Alberta, in 1989 to investigate the effects of conventional tillage, zero tillage, and four levels of nitrogen fertilizer on continuous barley production. In both tillage systems, the nitrogen was banded 6 to 8 cm deep between alternate barley rows. Herbicides were used for weed control each year. The influence of tillage and nitrogen on weed seed population dynamics was determined in 1991 and 1992. In the zero-tillage system, a large proportion of the weed seeds were present either at the soil surface or at the 5- to 10-cm depth. Green foxtail, the dominant species at Alliance, was also present at Hairy Hill where field pennycress was dominant. Green foxtail was consistently associated with low (residual) nitrogen and, in most cases, with conventional tillage. At both locations, green foxtail populations tended to decrease to very low levels as nitrogen rate increased, especially in zero tillage. At Hairy Hill, field pennycress populations in the soil seedbank were higher in zero tillage compared with conventional tillage, but plants that emerged from the soil seedbank in the field in spring were lower in zero tillage. Field pennycress populations were highest under low nitrogen. The results indicate that banding nitrogen has the potential to be an effective tool for green foxtail and field pennycress management in conventional- and zero-tillage systems, resulting in less dependence on herbicides for their control.

. 2008. Impact of agronomic factors on seed yield formation and quality in flax. Can. J. Plant Sci. 88: 485Á500. Flaxseed is known to have significant health benefits in human nutrition and when included in animal rations. There is pressing need to improve flaxseed production to meet the growing demand. The objective was to study the effects of three seeding rates (22, 45 and 67 kg ha(1 ), two seeding dates (early May and late May), three rates of nitrogen (66, 100 and 133% of recommended) and three cultivars (Norlin, AC McDuff and CDC Valour) and at five locations representative of the flax-growing area of the Canadian prairies from 1999 to 2001. The variables of interest were plant density, seed yield and yield formation, seed oil content and oil quality. Plant establishment was always highest with Norlin, but bolls m (2 was similar between the three cultivars. Plant density was always highest with the later plantings. No overall effect of seeding date was observed on grain yield, but the site-year by seeding date interaction showed that the later planting was favoured by the most northerly sites and early planting at the most southerly sites. The sites intermediate in latitude showed little response to seeding date. This finding provides important information with respect to the inclusion of flax in cropping systems depending on the latitude and deciding on the order of planting. Later planting resulted in a small decrease in oil content. Seed yields were increased with seeding rates going from 22 to 45 kg ha (1 with little effect on seeds boll (1 . Seeding rate had no effect on seed oil quantity and quality and maturity. A seed yield increase was observed with nitrogen when going from 66 to 100% of the recommended rate with no increases past 100%. Adding nitrogen resulted in a small drop in seed oil content. The seeding date )nitrogen rate interaction revealed a lack of response to nitrogen with the later planting date beyond 66% of the recommended N rate, suggesting reduced nitrogen rates with later plantings are possible. The absence of a site-year by seeding date by nitrogen rate interaction implies that findings of this study can be applied to a wide geographical area. In conclusion, attention needs to be given to seeding rates to target plant density !300 plants m (2 . Even with the high seeding rates, the target plant population was achieved only 60 and 73% of the time for the early and late planting, respectively. Using soil test recommendations for nitrogen will maximize seed yields under most situations. Best agronomic practices to maximize seed yield were found to maintain adequate seed oil quality and quantity.Key words: Linum usitatissimum L., nitrogen rate, seeding rate, seeding date, cultivar Lafond, G. P., Irvine, B., Johnston, A. M., May, W. E., McAndrew, D. W., Shirtliffe, S. J. et Stevenson, F. C. 2008. Impact des facteurs agronomiques sur le rendement grainier et la qualite´du lin. Can. J. Plant Sci. 88: 485Á500. On sait que le lin a d'importants bienfaits pour la sante´en nutrition humain...

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wild oat (Avena fatua L.) in tame oat (Avena sativa L.) with early seeding dates and high seeding rates. Can. J. Plant Sci. 89: 763Á773. Traditionally, farmers have delayed seeding to manage wild oat (Avena fatua L.) in tame oat (Avena sativa L.) crops, but this practice can adversely affect grain yield and quality. The objectives of this study were: (1) to evaluate the effectiveness of using high seeding rates with early-seeded oat to maintain grain yield and quality, and (2) to determine an optimum seeding rate to manage wild oat and maximize grain yield and quality. The factors of interest were wild oat density (low and high density), seeding date (early May, mid May, early June and mid June), and tame oat seeding rate (150, 250, 350 and 450 viable seeds m (2 ). The study was conducted at Indian Head and Saskatoon, SK, in 2002, 2003and 2004, at Winnipeg, MB, in 2002, and at Morden, MB, in 2003and 2004. Wild oat biomass, wild oat panicle density and wild oat seed in the harvested sample decreased as seeding rate increased, while tame oat biomass and grain yield increased. Wild oat density ranged between 0 and 100 plants m (2 with averages of 10 plants m (2 in the low density treatment and 27 plants m (2 in the high density treatment. At low seeding rates, grain yield decreased with increasing wild oat density. The difference in grain yield between the two wild oat densities decreased as the seeding rate increased. There was a curvilinear decrease in grain yield as seeding was delayed. A seeding date )seeding rate interaction was noted for test weight, plump seed, thin seed and groat yield. Seed quality improved as seeding rate increased for only the mid-June seeding date. Even though the mid-June test weight increased as the seeding rate increased it was always lower than the early May test weight at any seeding rate. The results from this study established that in the presence of wild oats, early seeding of tame oat is possible providing high seeding rates, 350 plants m (2 , are used. . La biomasse, la densite´des panicules et le nombre de semences de folle avoine dans l'e´chantillon diminuent quand la densite´de semis augmente; paralle`lement, on note une hausse de la biomasse et du rendement grainier de l'avoine. La densite´de peuplement de la folle avoine varie de 0 a`100 plants au m 2 , avec une moyenne de 10 plants au m 2 pour le traitement a`faible densite´et de 27 plants au m 2 pour celui a`densite´e´leve´e. À une faible densite´de semis, le rendement grainier diminue quand augmente la densite´de peuplement de la folle avoine. L'e´cart entre le rendement grainier aux deux densite´s de peuplement de la folle avoine se re´tre´cit avec l'augmentation de la densited es semis. Retarder les semis entraıˆne une diminution curviline´aire du rendement grainier. Les auteurs ont observe´une interaction entre la date des semis et la densite´de semis pour le poids spe´cifique, la proportion de grains ventrus, la proportion de grains minces et le rendement en gruau. La qualite´des semences s'ame´liore avec la hau...

May, W. 2003. Management of nitrogen and phosphorus fertilizer in no-till flax. Can. J. Plant Sci. 83: 681-688. The major flax-growing areas of Canada coincide with areas where large shifts towards conservation tillage have occurred. These shifts have also brought about major changes in the way fertilizer is applied. The objective of this study was to determine the combination of nitrogen fertilizer form and N and P fertilizer placement methods that can increase N and P uptake, seed yield and seed oil concentration and composition in flax. The study was conducted at four locations covering the flax-growing areas over a 3-yr period. Three fertilizer forms, ammonium nitrate (AN), ammonium sulphate (AS) and urea were compared using different placement methods, pre-plant band (Pp) or side-band (Sb) in combination with monoammonium phosphate in either a Pp, Sb or seed-placed (Sp) position. Plant uptake of N and P was measured at 7, 14, 21 and 28 d after crop emergence and at the start of flowering. Other variables collected included crop establishment, crop yield and seed oil concentration and composition. AS resulted in the highest N uptake followed by AN then urea. As well, AS in the Sb showed higher N uptake than when applied Pp. The largest uptake of P was observed on days 7, 14 and 21 when AS and P were placed together in an Sb position. Crop establishment was adversely affected by urea and least by AN and AS, indicating that adequate seed-fertilizer separation between urea and flax seed is critical to minimizing reductions in plant stands. N form and placement, and P placement had no effect on seed oil concentration and composition in this study. Seed yield was improved marginally, overall, with the addition of P, while changes in N and P placement had no overall yield benefits. Treatments that resulted in improved N and P uptake in the first 21 d after crop emergence did not result in improved seed yields. When site × year interactions were investigated, 2 of 12 site years showed better yields when N and P were placed together in the Sb position. Based on the results of this study, we conclude that flax growers have many agronomically acceptable N and P management options available. Parmi les autres variables examinées, signalons l'établissement de la culture, le rendement ainsi que la concentration en huile et la composition de cette dernière. Le SA engendre la plus forte absorption de N, suivi par le NA et l'urée. Le SA agit davantage sur la quantité de N absorbée quand il est placé Sb plutôt que Pp. L'absorption la plus forte de P a été relevée les 7 e , 14 e et 21 e jours quand le SA et le P sont appliqués ensemble de façon Sb. La culture s'établit plus mal avec l'urée qu'avec le NA et le SA, signe qu'il est essentiel de bien séparer la semence et l'urée pour obtenir les peuplements les plus denses. Selon les résultats de l'étude, le genre d'engrais N et la méthode de placement, ainsi que la méthode de placement des engrais P n'ont aucune incidence sur la concentration d'huile dans la graine ni la composi...

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Bean anthracnose, caused by Colletotrichum lindemuthianum, can severely reduce bean yield and seed quality. A 2-year field study at two sites in southern Manitoba examined the effect of the timing of foliar applications of the fungicide pyraclostrobin (Headline ® 250 EC) on the control of bean anthracnose in navy bean (Phaseolus vulgaris) 'Navigator'. Single and (or) sequential applications of pyraclostrobin at a rate of 0.1 kg active ingredient (a.i.)/ha were made at four growth stages. Single applications of pyraclostrobin, at either 3 to 5 trifoliolate leave stage, early flowering (40% bloom), late flowering (80% bloom), or 10 days after flowering, reduced disease development in the crop canopy, but had inconsistent effects on pod infection, seed discoloration, and yield. Sequential applications of pyraclostrobin at the early and late flowering stages usually resulted in the lowest disease severity on all parts of the plant and in the highest yield. Sequential applications of pyraclostrobin at the late flowering stage and 10 days after flowering were less effective in reducing anthracnose severity and seed discoloration than the earlier sequentialapplication treatment. Both sequential-application treatments of pyraclostrobin had similar yields. Under Manitoba growing conditions, seed-borne infection by C. lindemuthianum resulted in yield reductions that ranged from 15.2% to 32.1% in the untreated bean plots.Résumé : L'anthracnose, causée par le Colletotrichum lindemuthianum, peut grandement réduire le rendement et la qualité de la graine de haricot. Une étude de 2 ans, menée à deux sites du sud du Manitoba, a permis d'examiner les effets du calendrier d'application foliaire de pyraclostrobine (Headline ® 250 EC), un fongicide, sur la lutte contre l'anthracnose du petit haricot blanc (Phaseolus vulgaris) 'Navigator'. Des applications uniques ou répétées de pyraclostrobine à la concentration de 0,1 kg de matière active à l'hectare ont été faites à quatre stades de développement. Des applications uniques de pyraclostrobine, que ce soit au stade de 3 à 5 feuilles trifoliolées, de début de floraison (40% de fleurs écloses), de fin de floraison (80% de fleurs écloses) ou de 10 jours après la floraison, ont réduit le développement de la maladie dans le couvert végétal, mais ont eu des effets variables sur l'infection des gousses, la décoloration des graines et le rendement. Des applications répétées de pyraclostrobine aux stades du début ou de fin de floraison ont généralement permis de réduire l'intensité de la maladie à son minimum sur toutes les parties de la plante et d'obtenir les rendements les plus élevés. Les applications répétées de pyraclostrobine aux stades de fin de floraison et de 10 jours après la floraison ont été moins efficaces à réduire l'intensité de l'anthracnose et la décoloration des graines que les applications répétées faites plus tôt. Les deux traitements avec des applications répétées ont procuré des rendements similaires. Dans les conditions de croissance du Manitoba, l'infection séminicole...