Optimal N fertilizer rates for maximum economic yield of sunola

Non-Peer ReviewedA 3-year study was established at Melfort in the Black soil zone and at Scott in the Dark Brown soil zone in 1993 to determine optimal rates of N fertilizer for maximum economic yield (M.E.Y.) of sunola under different tillage systems. Likely because of good soil moisture conditions during the growing season, there was no difference between conventional tillage and direct seeded plots in sunola yield response to N fertilization at either location. As expected, a higher rate of N fertilizer was required to attain M.E.Y. at Melfort than at Scott because of the greater yield potential in the Black soil zone

Implication of reduced herbicide rates on resistance enrichment in wild oat (Avena fatua)

Non-Peer ReviewedModel simulations predict that lowering herbicide efficacy by reducing the application rate would slow the rate of enrichment of herbicide-resistant individuals in a weed population, but the resulting increase in density of susceptible plants would reduce crop yield and increase the weed seedbank. A study was conducted at three sites in Saskatchewan from 1997 to 2000 to examine the implication of reduced rates of Group 1 herbicides in a 4-year crop rotation, in conjunction with variable crop seeding rates, on the enrichment of resistant wild oat in a mixed (resistant and susceptible) population. Main plot treatments were crop (barley, canola, field pea, spring wheat), subplot treatments were crop seeding rate (recommended and high), and sub-subplot treatments were Group 1 herbicide rate (0, 0.33, 0.67, and 1.0 times the recommended rate). Herbicide rate frequently interacted with seeding rate in affecting wild oat seedling density, seed return, the viable fraction of the weed seedbank, and crop seed yield. As simulation models predict, reduced herbicide efficacy decreased the proportion of resistant individuals in the population. The high crop seeding rate compensated for a one-third reduction in herbicide rate by limiting total wild oat seed return and by reducing the number of resistant seedlings recruited from the seedbank. In a diverse cropping system, the level of resistance in the seedbank can be reduced without increasing the total (resistant plus susceptible) seedbank population by manipulating agronomic practices to increase crop competitiveness against wild oat when Group 1 herbicide rates are reduced to a maximum of two-thirds of that recommended

Competitive ability of hybrid and open-pollinated canola (Brassica napus) with wild oat

Non-Peer ReviewedThe competitiveness of three hybrid and three open-pollinated canola cultivars against two wild oat populations was determined under controlled environment conditions at two plant densities and five canola:wild oat ratios. Analysis of replacement series and relative crowding coefficients (RCC), based on shoot dry weight or leaf area, indicated that hybrid canola cultivars were twice as competitive than open-pollinated cultivars when weed interference was relatively high (i.e., high plant density and vigorous wild oat growth). Little difference in competitiveness among cultivar types was apparent when weed interference was lower. The results of this study suggest that hybrid canola cultivars may be best suited for use in an integrated weed management program, particularly for farmers of organic or low input cropping systems

Ammonia volatilization from manure in cropping systems for ethanol production

Non-Peer ReviewedEffect of tillage on ammonia (NH3) volatilized from fresh and com posted farmyard manure (FYM) used for fertilizing barley (Hordeum vulgare L.), was determined at two sites near Melfort, Saskatchewan in 1993. Ammonia losses were markedly higher in plots under zero tillage than under conventional tillage, as well as in plots which received a high rate (90 t ha-1) of FYM versus a lower rate (22 t ha-1). In conservation tillage cropping systems in which FYM is not incorporated into soil, the amount ofNH3 volatilized is not very large when FYM-N rates are comparable to crop requirements

Transgenic crops : new weed problems for Canada?

Over 25 000 transgenic field trials were conducted globally from 1986-1997, and many transgenic crops, including soybean (Glycine max), maize (Zea mays), tobacco (Nicotiana tabaccum), cotton (Gossypium hirsutum), canola (Brassica napus, B. rapa), tomato (Lycopersicon esculentum) and potato (Solarium tuberosum) have been commercially released. There has been a high adoption rate, with at least 28 million ha reported for 1998, with herbicide- and insect-resistant plants occupying 71 and 28% of the releases, respectively. The current status of commercial production of transgenic crops in Canada is summarized. Transgenic crops have the potential to change weed communities/populations in three principal ways, via: 1 ) escape and proliferation of the transgenic plants as 'weedy' volunteers with subsequent displacement of the crop, weed and/or natural vegetation; 2) hybridization with and transgene infiltration into related weedy and/or wild species, resulting in invigorated weeds and/or alteration of natural gene frequencies in these species; and 3) genetic changes in populations of unrelated species, as a result of changes to the environment, in particular herbicide-resistant (HR) transgenic crops and the development of HR weeds. Potential risk can be estimated a priori using knowledge of the systematics of crop/wild/weed complexes. Risk must be assessed on a case-by-case basis for each crop, each country/ecological region, and for each trait. Potential weed risks will be greater if crop volunteers are predisposed to becoming weedy, are well adapted to the Canadian climate and if sexually compatible wild species are present

Current state of herbicide resistance in Canada

Non-Peer ReviewedBiotypes of wild oat (Avena fatua L.) resistant to Group 1 herbicides in the prairie provinces, and biotypes of chickweed [Stellaria media (L.) Vill.] and kochia [Kochia scoparia (L.) Schrad.] in western Canada and pigweed (Amaranthus) species in Ontario resistant to Group 2 herbicides are most abundant and widespread. Evolution of resistance in these biotypes is attributable to frequent use of herbicides from these two respective groups. Increasing incidence of wild oat populations with multiple-group resistance will threaten the future effectiveness of herbicides of different modes of action. Proactive or reactive management for herbicide resistance in weeds must consider the risks of herbicides of different modes of action to select for resistance and the differing propensity of herbicides to be metabolized in herbicide-resistant biotypes when rotating among herbicides, must meet criteria for effective herbicide mixtures, and should incorporate agronomic practices in cropping systems that help reduce weed seed production and spread

Predicting the amount of nitrate-nitrogen and water in the soil profile

Non-Peer ReviewedFour simulation models were used to predict the amount and distribution of nitrate-N and water in soil from long-term spring wheat (Triticum aestivum L.) rotations at the end of the 1990 growing season at Melfort, Saskatchewan. There were significant differences between models in accurately simulating the nitrate-N and water status of the soil profile

Survey of herbicide-resistant wild oat (Avena fatua L.) in two townships in Saskatchewan

Non-Peer ReviewedThe objective of this study was to determine the nature and occurrence of herbicide resistance in wild oat in the Grassland and Parkland regions of Saskatchewan in 1997, based on a systematic survey of fields in two randomly selected townships. The survey found that: 1) over one-half of fields in both townships had populations resistant to Group 1, 2, and/or 8 herbicides; 2) fields in the Parkland township had higher mean levels of Group 1 resistance (% resistant seeds) than fields in the Grassland township, suggesting they were subjected to more Group-1 herbicide applications; and 3) single- (Groups 1, 2, or 8) and multiple-group resistance (1,2; 1,8; 2,8; 1,2,8) were exhibited in populations in fields in both townships. The proportion of fields with populations exhibiting Group 1 (single) resistance was higher, and Group 2 and Groups 1,2 resistance were lower in the Parkland compared to that in the Grassland township. In both townships, farmers with more land (within the township or total farmed) tended to have a greater proportion of that land infested with Group 1- or 2-resistant wild oat compared to those with less land. The nature of resistance in wild oat populations in Saskatchewan is more diverse, differences in distribution and abundance of resistant biotypes between Grassland and Parkland regions are generally less apparent, and occurrence of resistance is more prevalent than previously documented

Management of herbicide-resistant wild oat (Avena fatua) patches

Non-Peer ReviewedA study was conducted at a 64-ha site in western Canada to determine how preventing seed shed from herbicide-resistant wild oat affects patch expansion over a 6-yr period. Seed shed was prevented in two patches and allowed to occur in two patches (untreated controls). Annual patch expansion was determined by seed bank sampling and mapping. All crop management practices were performed by the grower. Area of treated patches increased by 35% over the 6-yr period, whereas untreated patches increased by 330%. Patch expansion was attributed mainly to natural seed dispersal (untreated) or seed movement by equipment at time of seeding (untreated and treated). Extensive seed shed from plants in untreated patches before harvest or control of resistant plants by alternative herbicides minimized seed movement by the combine harvester. Although both treated and untreated patches were relatively stable over time in this cropping system, preventing seed production and shed in herbicide-resistant wild oat patches can markedly slow the rate of patch expansion

Alberta field survey of herbicide-resistant weeds

Non-Peer ReviewedIn 2001, 236 fields were randomly selected throughout the ecoregions of Alberta and surveyed for grass and broadleaf weeds resistant to Group 1 (ACCase inhibitor) or Group 2 (ALS inhibitor) herbicides. Nearly 20% of surveyed fields had a herbicide-resistant weed biotype. Only 5% of producers with resistant biotypes were aware of their occurrence. This survey serves as a baseline for determining future trends in weed resistance in Alberta