The effect of row spacing and seeding rate on the yield of Brassica campestris L. and B. napus L. was studied for 2 yr in northwest Alberta. Rows were spaced 7.5, 15 and 23 cm apart with seeding rates of 7 and 14 kg/ha at each spacing. Decreasing row spacing from 23 cm to 15 cm and from 15 cm to 7.5 cm increased yields by an average llVo and 337o, respectively. Seeding rate had no significant effect on yield.

The effect of row spacing on seed and hay yields of 11 perennial grass species, including crested wheatgrass (Agropyron cristatum L.), intermediate wheatgrass (A. intermedium (Host.) Beauv.), a northern biotype of bromegrass (Bromus inermis Leyss.), a southern biotype of bromegrass, Russian wildrye (Elymus junceus Fisch.), meadow fescue (Festuca pratensis Hudson), creeping red fescue (F. rubra var. genuina L.), chewings fescue (F. rubra var. commutata Gaud), reed canary grass (Phalaris arundinacea L.), a turf-type timothy (Phleum bertolonii DC (P. bulbosum auct.)) and hexaploid timothy (Phleum pratense L.), was studied under a system with limited inputs of fertilizer and no weed control. The width of the row spacings ranged from 16 to 104 cm where seed yields were measured and from 27 to 93 cm where hay yields were measured. The seed yield of all grasses was greater at a row spacing of 16 cm than at row spacings of 60 cm or more. Hay yields of all grasses, averaged over four production years, were also greatest at narrow row spacings (27 cm). These yields decreased as row spacings increased to 49 through 93 cm. Row spacing had its greatest effect on hay yields during the first production year. After this period the effects of row spacing on hay yields were small.Key words: Row spacing, perennial grasses, seed yields, hay yields

A field study was conducted from 1987 to 1992 to determine the effectiveness of several treatments consisting of combinations of glyphosate and/or quizalofop with tillage to control quackgrass in legume plowdown and continuous annual crop rotations. The treatments were imposed on the quackgrass in 1987 and/or 1988, evaluated in 1989 (cycle 1), reimposed on the same plots in 1990 and/or 1991 and re-evaluated in 1992 (cycle 2). Where continuous barley was grown, glyphosate applied at 0.45 kg/ha before seeding in 1987 (cycle 1) and 1990 (cycle 2), and combined with fall tillage in the first two years of each cycle, reduced quackgrass shoot density and rhizome dry weight by more than 96%. In a legume plowdown rotation, consisting of barley underseeded to red clover followed by plowdown and barley in subsequent years, quackgrass was reduced by a similar amount by glyphosate at 0.45 kg/ha applied in 1987 and 1990 before seeding or in 1988 and 1991 at 5 d before or 6 wk after red clover plowdown. Quackgrass reduction from all of these treatments was as effective as the labelled rate of glyphosate (0.90 kg/ha) applied at the same times, and also as effective as glyphosate applied at 0.45 kg/ha in combination with tillage in a year of fallow. Without fall tillage the efficacy of glyphosate applied before seeding was reduced. Quizalofop at 0.20 kg/ha applied to canola in a rotation of canola followed by two years of barley, reduced quackgrass, but was less effective than glyphosate treatments with fall tillage. Reducing quackgrass populations resulted in significant increases in crop yields.

A study was conducted on the Agriculture and Agri-Food Canada Research Farm, Beaverlodge, Alberta, to compare nine cropping systems in relation to productivity and wild oat (Avena fatua L.) control. The nine cropping systems consisted of three crop rotations and three levels of banded N fertilizer. Each cropping system had its own regime of tillage and weed control. One of the rotations consisted of mechanical fallow, along with canola (Brassica rapa L.), barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.), while the other two rotations consisted of the same annual crops, but with either flax (Linum usitatissimum L.) or red clover (Trifolium pratense L.) plowdown with partial fallow substituted for mechanical fallow. The three rates of banded N fertilizer were 0, 75 and 150% of recommended, based on soil tests and provincial recommendations. From 1991 to 1994, cropping systems with mechanical fallow and fall tillage after annual crops produced 24% higher total seed yields than cropping systems with no fall tillage after annual crops and either continuous annual crops or red clover plowdown. Increasing the rate of banded N fertilizer from 0 to 75% of recommended increased total crop seed yields but a further increase from 75 to 150% had no significant effect. Although cropping systems with mechanical fallow had an advantage over other cropping systems, the effect of crop sequencing and yearly weather conditions on total crop seed yields was greater than the effect of cropping systems. Wild oat populations varied greatly with year, but the ease of management was greater in cropping systems with the mechanical fallow than in other cropping systems. Wild oat density increased when diclofop or difenzoquat performed inadequately or when poor red clover establishment allowed populations to increase. Reductions in wild oat populations appeared to be largely due to the consistent effectiveness of sethoxydim. , alors que les deux autres consistaient en une rotation des mêmes cultures annuelles plus la culture de lin (Linum usitatissimum L.) ou celle de trèfle rouge (Trifolium pratense L.) comme engrais vert, puis jachère partielle à la place de la jachère mécanique. L'engrais azoté a été épandu à un taux correspondant à 0, à 75 ou à 150 % du taux recommandé après analyse du sol et selon les recommandations provinciales. De 1991 à 1994, les régimes avec jachère mécanique et travail du sol à l'automne après récolte des cultures annuelles ont présenté un rendement grainier de 24 % supérieur à celui des systèmes sans retournement du sol à l'automne et culture continue ou utilisation de trèfle rouge comme engrais vert. Quand la fertilisation passe de 0 à 75 % du taux recommandé, on assiste à une hausse du rendement grainier, mais doubler la quantité d'engrais azoté de 75 à 150 % n'exerce aucun effet sensible sur la récolte. Bien que les systèmes agricoles avec jachère mécanique présentent un avantage sur les autres régimes, la succession des cultures et les conditions météorologiques durant l'année agissent plus sur l...