The contribution of nitrogen (N) fertilizer placement to management of annual weeds in spring wheat grown under two tillage systems was examined at sites located in three ecoregions of the northern Great Plains from 1994 to 1996. The effect of three different fertilizer placements on narrowleaf and broadleaf weed emergence, growth, and N uptake were determined in a no-till and a conventional tillage system. Fertilizer was broadcast, subsurface-banded in the spring prior to seeding, or side-banded at the time of seeding. Tillage system generally did not influence weed and crop response to fertilizer placement. Broadcast-applied fertilizer was more effective than banded fertilizer in promoting wild oat and broadleaf weed emergence and growth over the growing season. Weed densities, biomass, and N uptake measured early in the growing season averaged 20 to 40% less, and grain yield of wheat at maturity averaged 12% higher where fertilizer was side-banded compared to broadcast. In contrast, the addition of fertilizer, regardless of placement, was detrimental to green foxtail because of enhanced crop competitiveness. Banding fertilizer at recommended rates can be an effective cultural practice for managing weeds in no-till and conventional tillage wheat-cropping systems in semiarid to subhumid regions of the northern Great Plains, but it is not reliable when used as the sole method of weed management.

2000. Herbicide-tolerant canola: weed control and yield comparisons in western Canada. Can. J. Plant Sci. 80: 647-654. Field experiments were conducted at five western Canadian locations in 1996 and 1997 to compare weed control and canola (Brassica napus L.) seed yields in the three major herbicide-tolerant canola (HTC) systems. The main objective of this study was to determine if significant weed control and yield advantages could be expected by using herbicides "designated" for HTC compared to a more "standard" application of sethoxydim plus ethametsulfuron. In 3 of 10 site-years, glyphosate in Quest canola and imazethapyr/imazamox in 45A71 canola provided a yield advantage over the standard treatment. The yield advantages were restricted to the Lacombe and Lethbridge sites and ranged from 13 to 39% increases over the sethoxydim plus ethametsulfuron treatments. Among the HTC, weed control was usually greatest with glyphosate, followed by imazethapyr/imazamox, and then glufosinate. Glufosinate efficacy was often restricted due to advanced growth stages on some weeds. The standard treatment of sethoxydim plus ethametsulfuron did not provide better weed control than glyphosate, but in some cases did improve weed control compared to imazethapyr/imazamox or glufosinate. The HTC provide growers with new opportunities for the control of difficult weeds along with the option to employ in-crop herbicides with new modes of action in canola. Des expéri-ences au champ ont été réalisées en 1996 et 1997 à cinq emplacements de l'ouest canadien pour comparer l'effet des méthodes de désherbage sur le rendement grainier du colza canola (Brassica napus L.) dans les trois principales régions de culture de canola tolérant aux herbicides (CTH). Il s'agissait surtout de déterminer si on pouvait attendre des avantages significatifs, au plan de désherbage et à celui du rendement grainier de l'emploi des herbicides spécifiquement désignés pour les systèmes CTH, plutôt que des traitements standards séthoxydim avec éthametsulfuron. À trois des dix emplacements-années, l'emploi du glyphosate sur cultivar Quest et de l'imazéthapyr/imazamox sur cultivar 45A71 a donnait lieu à des gains de rendement par rapport au traitement courant. Cet avantage qui, par ailleurs, se limitait aux emplacements de Lacombe et de Lethbridge fluctuait de 13 à 19 % par rapport au traitement standard. Parmi les trois régimes CTH, la meilleure efficacité de désherbage était habituellement obtenue avec l'emploi du glyphosate, suivi par celui de l'imazéthapyr/imazamox et enfin du glufosinate. L'efficacité de ce dernier herbicide était souvent restreinte par le stade de croissance avancé de certaines mauvaises herbes au moment du traitement herbicide. Le traitement standard séthoxydim plus éthametsulfuron n'apportait pas un meilleur désherbage que celui au glyphosate, mais dans certains cas il se révélait supérieur à cet égard aux traitements au imazéthapyr/imazamox ou au glufosinate. La culture de cultivar de canola tolérant aux herbicides fournit aux producteurs de ...

In experiments conducied from 1988 io iSSO at four locations in the Parkland zone of western Canada, the drydown of seed and foliage, seed yield, seed quality and baking quality of wheat (Titicum aestivarn L.) following preharvest applications of glyphosaie were compared with moie following windrowing prior to harvest or direct cutting of the standing crop. Glyphosate wai applied in late July to early September at rates of 0.45,0.9 and 1.7 kg acid equivalent ha-'to wheat with seed moisture contents ranging from 80 to ll%. When compared with a standing crop, all glyphosate treaunents applied at seed moisturg c9n-tents above 25% slightly enhanced the drydown of wheat seed and foliage. Treatments applied at seed moisture contents below 25% had no effect on either seed or foliage drydown. Seed yields were generally greater from plots to which glyphosate was applied than from windrowed control plots, although in one of five experiments the reverse trend occurred. Increasing the rate from 0.45 to 1.7 kg ha-r had no effect on yield. Windrowing or applying glyphosate to wheat with a seed moisture content of 6l% or more reduced yields more than windrowing or applying glyphosate at seed moisture contents below this level. In experiments where the wheat in both control and sprayed plots wasdirect cut at maturity, average yields decreased as the rate of glyphosate increased from 0 to 1.7 kg ha-l. However, applications at seed moisture of 40% or less, caused little or no yield loss. ihere was little or no difference in 1000-seed weight, sample density, seed germination and protein content from plots sprayed with glyphosate at seed moisture contents below 40% than from control plots windrowed at the same moisture content oi direct cut at maturity. Baking quality was not affected by any of the glyphosate treafinents in experiments where the wheat was harvested by direct cutting.Key words: Glyphosate, wheat, desiccation, wheat quality, Triticum aestivum Darwent, A. L., Kirkland (Sheppard et al. 1982). In Canada, investigations by Clarke (1981) (Fig. 1) Lacombe (88) Lacombe (89) Beaverlodge (88) Beaverlodge (89) Beaverlodge (90) Melfort ( All statistical analyses were performed using release 2.1 of GENSTAT (Iawes Agricultural Trust 1990). RESULTS Seed and Foliage DrydownSeed moisture content was influenced by the factors location, rate of glyphosate, time of sampling and seed moisture class and by the interactions location, rate ofglyphosate and seed moisture class with time of sampling ( Table 2). None of the three-way interactions was significant.The drydown of wheat seed was enhanced by the application of glyphosate. Mean seed moisture content, averaged across locations and seed moisture classes, was similar in all plots at 5 d after application, but was 3.6, 5.0 and 17 .2Vo lower in glyphosate-sprayed plots than in control plots at 1988, 1989 and 1990. seeds and converting to g per 1000 seeds. After weighing, these seeds were subjected to standard germination tests Baking quality. The effect of the glyphosate trea...

. 2002. Nitrogen fertilizer placement for fall and spring seeded Brassica napus canola. Can. J. Plant Sci. 82: [15][16][17][18][19][20]. Brassica napus L. canola seeded in the fall (dormant) just prior to freeze-up, or in the early spring as soon as fields are passable, can improve productivity in semiarid regions on the Canadian prairies. The objective of this study was to assess N fertilizer placement options for alternative canola seeding dates. Herbicidetolerant B. napus canola (cv. Quest) seedling density, phenological development, seed yield, seed weight, oil concentration, and protein concentration were assessed for four N (urea) placement options [banded prior to fall seeding date (only Melfort), broadcast in early-spring, side banded, and seed placed] and three seeding dates (late October, mid-to late April, and mid-May) at Scott and Melfort, SK, Canada. Nitrogen fertilizer placed with the seed often reduced seedling density. At Melfort, seed placed N fertilizer reduced the seed yield (10%), seed oil concentration (4%) and increased protein concentration (5%) of fall and mid-May seeded canola. The other N fertilizer placement options consistently maintained the highest level of canola production for all seeding dates. At Scott, seeding canola in fall or April generally maintained adequate plant stands, and often increased seed yield (43%), seed weight (18%), and oil concentration (5%), when compared with the mid-May seeding date. Our results indicate that N fertilizer placement considerations used for the more traditional mid-May seeding date should be similar for canola dormant or April seeded. Current N fertilizer placement options, such as side banding, pre-plant banding or early-spring broadcasting, are options that resulted in equivalent crop yield responses. Given the variability in crop yield response measured with seed placement of N, we recommend that this practice should be avoided. ) à l'automne, juste avant le gel, ou au début du printemps, dès que les champs deviennent praticables, on peut améliorer la productivité de cette culture dans les régions semi-arides des Prairies canadiennes. L'étude devait préciser les techniques d'amendement azoté envisageables à d'autres dates de semis. Les auteurs ont évalué la densité de peuplement, la phénologie, le rendement grainier, le poids des semences, la teneur en huile et la concentration de protéines de la variété de canola Quest, tolérante aux désherbants, pour quatre techniques avec de l'urée -application en bande avant les semis automnaux (à Melfort seulement), à la volée au début du printemps, en bandes latérales et directement avec la semence -à trois dates d'ensemencement (fin octobre, du milieu à la fin d'avril et mi-mai), à Scott et à Melfort, en Saskatchewan (Canada). En déposant l'engrais azoté avec la semence, on réduit souvent la densité du peuplement. À Melfort, cette technique a diminué le rendement grainier (10 %) et la teneur en huile des graines (4 %), mais augmenté la concentration de protéines (5 %) du canola semé à l'automne et à...

In a 2-yr study at four locations in western Canada, residues of glyphosate and its major metabolite aminomethyl-phosphonic acid (AMPA) were measured in the seed and foliage of wheat (Triticum aestivum L.) following preharvest applications at rates of 0.45, 0.9 or 1.7 kg acid equivalent ha−1. Herbicide treatments were applied in early August to mid-September at seed moisture contents ranging from 52 to 12%. Glyphosate and AMPA residues in the seed increased as the rate of application increased, and decreased as the seed moisture content at the time of application decreased. However, when the maximum application rate of 1.7 kg ha−1 was sprayed at seed moisture contents of 40% or less, glyphosate residues in the seed were < 5 mg kg−1, the Maximum Residue Level recently established by Health Canada. Glyphosate and AMPA residues in the straw also increased with increasing application rate, but there was no consistent pattern in residues of either chemical with seed moisture content at the time of application. Physiological maturity of the crop, rainfall washoff, and application rate appeared to play important roles in determining the magnitude of glyphosate and AMPA residues in the seed and straw of wheat. Key words: Glyphosate, AMPA, residues, wheat, seed, preharvest application