Russian thistle (Salsola tragus L.) is among the most troublesome weeds in cropland and ruderal semiarid areas of the Pacific Northwest (PNW). Predicting S. tragus emergence timing plays a critical role in scheduling weed management measures. The objective of this research was to develop and validate a predictive model of the seedling emergence pattern of S. tragus under field conditions in the PNW to increase the efficacy of control measures targeting this species. The relationship between cumulative seedling emergence and cumulative hydrothermal time under field conditions was modeled using the Weibull function. This model is the first to use hydrothermal time units (HTT) to predict S. tragus emergence and showed a very good fit to the experimental data. According to this model, seedling emergence starts at 5 HTT, and 50% and 90% emergence is completed at 56 HTT and 177 HTT, respectively. For model validation, independent field experiments were carried out. Cumulative seedling emergence was accurately predicted by the model, supporting the idea that this model is robust enough to be used as a predictive tool for S. tragus seedling emergence. Our model can serve as the basis for the development of decision support systems, helping farmers make the best decisions to control S. tragus populations in no-till fallow and spring wheat systems.

Increasing crop diversity has been proposed to increase the sustainability of cropping systems. If producers are to adopt these systems, they should also be economically viable. In this study conducted near Mandan, North Dakota, four no-till cropping systems with varying levels of crop diversity were evaluated over a 12-yr period to quantify system effect on crop productivity, input use, production costs, and economic risks and returns. Cropping system treatments included a small grain–fallow rotation (SG–Fallow) and a continuous spring wheat (Triticum aestivum L.) rotation (Cont SW) as baseline low-diversity rotations, a small grain–winter wheat (T. aestivum L.)–sunflower (Helianthus annuus L.) rotation (SG–WW–Sun), a 5-yr rotation (Five Year) and a dynamic rotation (Dynamic). The SG–Fallow rotation was significantly less productive and less profitable on average than the other rotations, as measured by gross returns and net returns, respectively. However, SG–Fallow also used significantly less inputs than the other rotations. Production costs for the Cont SW and SG–WW–Sun rotations showed a significant increasing trend over time, while production costs for the Five Year rotation showed a significantly lower and slight decreasing trend over the period, with cost trends for the SG–Fallow and Dynamic rotations intermediate to these. Net returns tended to increase and relative economic risk tended to decrease as crop diversity increased from SG–Fallow and Cont SW to SG–WW–Sun, Five Year and the Dynamic system. Results from this study suggest that more diverse rotations can maintain or increase crop productivity and enhance economic viability.

The robustness of competitive attributes of cereals such as rapid and uniform seedling emergence, tillering, early biomass accumulation and canopy closure, and height advantage over weeds have not yet been tested under environmental conditions typical of no-till (NT) cropping systems. Our objective was to evaluate the effects or NT practices on growth and productivity of Avena sativa, Triticum aestivum, Hordeum vulgare, and associated weeds. The experiment was conducted on a Kamouraska clay at La Pocatière, QC, in 1994, 1995, and 1996. Avena sativa, T. aestivum, and H. vulgare were grown under tilled and NT practices. Cereal growth parameters were measured six (1994) or seven (1995) times between planting and the 11th week after planting but only once in 1996. Grain yields and yield components were determined at crop maturity. Avena sativa and H. vulgare populations were little affected by tillage, whereas T. aestivum populations were reduced by 16 to 20% in NT systems. Growth in height in NT systems was either similar or greater than in tilled systems in all three cereals. Cereal leaf area index (LAI) and biomass accumulation was also comparable between tillage systems, except for T. aestivum LAI in 1994, which was greater in tilled plots on two sampling dates. Response of annual dicots to tillage was inconsistent in all crops. Annual monocots dominated in some but not all NT systems. Perennial dicots dominated in NT systems, whereas perennial monocots were more abundant in tilled systems in all three cereals. Avena sativa and T. aestivum yields in NT plots were comparable or greater than in tilled plots, in spite of having either lower test weights (A. sativa) or lower 1,000-grain weights (T. aestivum). NT T. aestivum productivity was maintained in spite of reduced plant establishment. Hordeum vulgare yields were also similar across tillage systems, except in 1995, when yields in tilled plots were greater than in NT plots. The height advantage observed for NT H. vulgare did not result in improved yields. All three cereals, and particularly A. sativa, appeared well suited to NT systems, despite the pressure provided by different weed groups, compared to tilled systems. However, results suggest that NT production of cereals could benefit from improved attention to perennial dicot control and crop seedling establishment, particularly for T. aestivum.

Two formulations of triallate [S-(2, 3, 3-trichloroallyl)diisopropylthiocarbamate] were evaluated for their effectiveness in controlling wild oat (Avena fatua L.) in spring wheat (Triticum aestivum L.) in 12 field experiments conducted between 1967 and 1978. Control of wild oat was greater with fall applications of triallate granules than liquid or with spring applications of either liquid or granules. Further-more, 1.1 kg/ha of triallate granules applied in the fall controlled wild oat as well as did 1.7 kg/ha of liquid triallate applied in the fall. Wild oat control with triallate was usually better when soil incorporated than when surface applied regardless of formulation or time of application. Triallate granules controlled wild oat similarly on either plowed ground or wheat stubble; whereas, liquid triallate controlled wild oat better on plowed ground than wheat stubble. A delay of 8 h in triallate incorporation did not reduce wild oat control with either formulation; however, a delay of 24 h reduced wild oat control with the liquid formulation.

Spring small grains were not as competitive with barnyardgrass and witchgrass as winter wheat. Winter wheat grain yields were greater than spring barley or spring wheat in 1986, 1987, and 1988 and oat in 1986 and 1988. Barnyardgrass, stinkgrass, and witchgrass control with glyphosate plus 2,4-D plus atrazine at 0.6 plus 0.8 plus 1.7 kg ha−1 was usually less when the herbicides were applied to stubble of spring small grain versus winter wheat due to the advanced weed growth at treatment Barnyardgrass and witchgrass were more difficult to control than stinkgrass, redroot pigweed, tumble pigweed, kochia, and tumble thistle. No-till corn planted into winter wheat stubble had fewer barnyardgrass and witchgrass than corn planted into spring wheat stubble. The addition of metolachlor plus atrazine at 1.7 plus 0.6 kg ha−1 eliminated differences among small grain cultivars in weed control in corn. Corn grain yields from winter wheat plots were greater than other small grains in 1989 because of better weed control and more crop residue.

Glyphosate-tolerant spring wheat currently is being developed and most likely will be the first major genetically engineered crop to be marketed and grown in several areas of the northern Great Plains of the United States. The public has expressed concerns about environmental risks from glyphosate-tolerant wheat. Replacement of traditional herbicide active ingredients with glyphosate in a glyphosate-tolerant spring wheat system may alter ecological risks associated with weed management. The objective of this study was to use a Tier 1 quantitative risk assessment methodology to compare ecological risks for 16 herbicide active ingredients used in spring wheat. The herbicide active ingredients included 2,4-D, bromoxynil, clodinafop, clopyralid, dicamba, fenoxaprop, flucarbazone, glyphosate, MCPA, metsulfuron, thifensulfuron, tralkoxydim, triallate, triasulfuron, tribenuron, and trifluralin. We compared the relative risks of these herbicides to glyphosate to provide an indication of the effect of glyphosate when it is used in a glyphosate-tolerant spring wheat system. Ecological receptors and effects evaluated were avian (acute dietary risk), wild mammal (acute dietary risk), aquatic vertebrates (acute risk), aquatic invertebrates (acute risk), aquatic plants (acute risk), nontarget terrestrial plants (seedling emergence and vegetative vigor), and groundwater exposure. Ecological risks were assessed by integrating toxicity and exposure, primarily using the risk quotient method. Ecological risks for the 15 herbicides relative to glyphosate were highly variable. For risks to duckweed, green algae, groundwater, and nontarget plant seedling emergence, glyphosate had less relative risk than most other active ingredients. The differences in relative risks were most pronounced when glyphosate was compared with herbicides currently widely used on spring wheat.

The ecological significance of species diversity within agroecosystems has become a point of interest in recent years. Although the time and spatial scale at which diversity is measured may influence the interpretation of its functional importance, little research has been conducted on methodological approaches to assess the number and relative abundance of agricultural plant species. In this study, we (1) evaluated the applicability of the species-area curve to examine plant species richness and α and β diversity in conventional no-tillage and organically managed spring wheat systems, and (2) assessed temporal changes in plant species richness across systems. Measurements were obtained at three times during two growing seasons in experimental plots and at three times during one growing season on commercial farms in Montana. In accordance with previous studies, management system affected species richness and diversity. In eight of nine studied cases, we detected a positive relationship between species richness and sampled area. In these eight cases, intercepts (α diversity) were higher for the organic systems than for the conventional no-tillage systems. Slopes (β diversity) were higher for the organic system in six of nine cases studied. Species richness declined as the season progressed for both systems, with the organic systems consistently having more species than the conventional no-tillage systems. Despite differences in the species composition and between the experimental plots and commercial farm field size, the patterns of species richness and α and β diversity were relatively constant, suggesting that the processes responsible for the assembly of plant communities in agroecosystems of the Northern Great Plains are similar at a range of spatial scales.

Strategies for pesticide use reduction have suffered from limited adoption. The impact of such strategies will be greater if they appeal to farmers with typical demographics and attitudes. A participatory, on-farm study was conducted to assess the potential of Pesticide Free ProductionTM (PFP) [Pesticide Free ProductionTM and PFPTM are registered trademarks of the University of Manitoba.] to be widely implemented on mainstream farms in Manitoba, Canada. PFP is a flexible, simple framework intended to appeal broadly to farmers who may not have adopted other pesticide use reduction initiatives. It may also provide a marketable food product label. This novel crop production system prohibits the use of in-crop pesticides and seed treatments during one crop year, as well as prior use of residual pesticides. Applications of nonresidual pesticides (such as glyphosate) are permitted prior to crop emergence. Synthetic fertilizer use is permitted at any time. The objectives of this study were: (1) to determine if the demographic and attitudinal characteristics of farms and farmers participating in a PFP pilot project varied depending on the level of PFP implementation; and (2) to compare the characteristics of farms and farmers participating in the pilot project with standards representing average farms and farmers in Manitoba. A total of 71 farmers, representing 120 fields and 11 crops, participated in the study. Fields and farmers were categorized into three groups, based on whether or not fields: (1) achieved PFP certification status and (2) were in transition to organic production. There were few demographic differences among groups. Demographic characteristics of participating farmers were typical for Manitoba, with the exception that participating farmers who were not in transition to organic production had higher levels of education than a random sample of Manitoba farmers. Attitudinal orientation (adherence to a conventional versus an alternative agricultural paradigm) of participants who were not in transition to organic production was similar to that of a random sample of Manitoba farmers. Fields and farms on which PFP was implemented were relatively large in the context of Manitoba averages. Participants indicated high satisfaction with certifiable PFP crops and high levels of interest in implementing future PFP. Pesticide free production demonstrates significant potential for broad adoption in this region.

Current production practices in the Red River Valley of North Dakota and Minnesota involve use of extensive tillage and/or herbicides to control weeds. Given the erosion potential, environmental concerns associated with herbicides, and herbicide-resistant weeds, alternative cropping systems that mitigate these problems need to be assessed economically. Furthermore, the role that government commodity programs play in the adoption of more ecologically friendly cropping systems needs to be determined. We evaluated 8 years of yield data (1994–2001) from field plots near Fargo, North Dakota, to compare the economics of two alternative cropping systems, reduced-input (RI) and no-till (NT), to a conventional tillage (CT) cropping system. The RI system relies on a more diverse rotation of soybean (SB), spring wheat (SW), sweet clover (SC) and rye, and uses fewer herbicide and fertilizer inputs than CT or NT. Both NT and CT systems rotate SB and SW. We found that CT returns averaged over $47 ha−1 more than NT during the study period. Because SC yield data were not available, the economic competitiveness of RI was calculated using break-even yields and returns for SC. Historical SC yields in Cass County, North Dakota were not statistically different from the break-even yields. However, when government program payments were considered, break-even returns for SC increased by about $15 and $18 ha−1 and break-even yields by 0.44 and 0.52 MT ha−1 for RI to compare with NT and CT, respectively. These results indicate that CT management offers greater economic return than either RI or NT and that government program payments impede adoption of more environmentally friendly cropping systems in the northern Great Plains.

Spring milling wheat (Triticum aestivum L em. Thell) and soybean (Glycine max L.) cultivars were managed to International Organic Certification Standards on two organically certified farms to evaluate two physical weed control methods, cultivar performance and quality. Nutrients were supplied as manure and compost. There was no difference (P<0.05) between flaming plus fingerweeding versus fingerweeding twice, 10 days apart, on weed control, yield, and protein in both crops. The spring wheat cultivar, AC Barrie, may be particularly well suited to production under an organic system, as indicated by its superior performance to AC Walton at the Springfield site in 2000, when growth conditions were favorable. A severe drought in 2001 limited the mineralization of soil and manure nitrogen, with the result that all spring wheat cultivars at the Springfield site did not make 13.5% grain protein, required to meet milling quality criteria. Also, in 2001 at both sites, soybean yields were reduced by 50% compared to 2000 because of reduced moisture availability and weed competition. Delays in field operations, lack of sufficient soil moisture and reduced mineralization of manure during the 2001 growing season were major factors in influencing crop production, especially at Springfield.

Results of calculations on the economic potential for alternative (low input, sustainable) farming systems in a small grain-row crop region of the Northern Plains are reported. Two sets of alternative farming systems, in which no chemical fertilizers or herbicides are used, are compared with various conventional and reduced till systems. In Farming Systems Study I (FSS1), an alternative rotation consisting of oats, alfalfa, soybeans, and corn is compared with conventional and ridge till rotation systems composed of corn, soybeans, and spring wheat. In Farming Systems Study II (FSS2), three systems with an emphasis on small grains are compared. An alternative system rotation consisting of oats, sweet clover, soybeans, and spring wheat is compared with conventional and minimum till rotation systems comprised of soybeans, spring wheat, and barley. Results of baseline economic analyses show that alternative farming systems can be competitive with more conventional systems in at least some situations. The alternative systems entail markedly lower direct costs, and the alternative system in FSS2 has approximately the same net returns as the comparable conventional and minimum till systems. The FSS1 alternative system has positive but somewhat lower net returns than the comparable conventional and ridge till systems. Sensitivity analyses were conducted with alternative system crop yields, chemical fertilizer and herbicide prices, and varying assumptions about future Federal farm program support levels and acreage set aside requirements. The yield sensitivity analyses show that one alternative farming system requires yields about 5–10 percent above those of the comparable conventional system to produce the same net returns. However, the other alternative system is competitive with a conventional system even with yields 5 percent lower. Analyses varying chemical fertilizer and herbicide prices reveal that the alternative farming system in FSS1 becomes competitive with more conventional systems when fertilizer and herbicide prices rise by 50 percent. The alternative farming system in FSS2 is already competitive at current fertilizer and herbicide prices. In some cases, sensitivity analyses with Federal farm program provisions indicate that reductions in farm program benefits increase the economic competitiveness of alternative farming systems. However, important exceptions occur. Results indicate that not only the level of future farm program benefits, but also the form of program provisions and compliance requirements, will affect the relative competitiveness of alternative farming systems.