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Kochia [Bassia scoparia (L.) A.J. Scott] is an invasive C4 tumbleweed in the Great Plains of North America, where it impedes crop harvest and causes significant crop yield losses. Rapid evolution and spread of glyphosate- and acetolactate synthase (ALS) inhibitor-resistant kochia in western Canada limit the herbicide options available for control of these biotypes in field pea (Pisum sativum L.); one of the predominant pulse crops grown in this region. Field experiments were conducted near Lethbridge, Alberta, in 2013–2015 and Coalhurst, Alberta, in 2013–2014 to determine which herbicide options effectively control glyphosate- and ALS inhibitor-resistant kochia in field pea. Visible injury of field pea was minor (0%–4%) in all environments except for Lethbridge 2013, where pre-plant (PP) flumioxazin and all treatments containing post-emergence (POST) imazamox/bentazon resulted in unacceptable (14%–23%) visible injury in field pea. Herbicide impacts on field pea yield were minor overall. Carfentrazone + sulfentrazone PP and saflufenacil PP followed by imazamox/bentazon POST resulted in ≥80% visible control of kochia in all environments, while POST imazamox/bentazon alone resulted in ≥80% reduction in kochia biomass in all environments compared with the untreated control (albeit, absent of statistical difference in Coalhurst 2014). These results suggest that layering the protoporhyrinogen oxidase-inhibiting herbicides saflufenacil or carfentrazone + sulfentrazone PP with the ALS- and photosystem II-inhibiting herbicide combination imazamox/bentazon POST can effectively control glyphosate- and ALS inhibitor-resistant kochia in field pea while also mitigating further selection for herbicide resistance through the use of multiple effective herbicide modes-of-action.

Kochia [Bassia scoparia (L.) A.J. Scott] is a summer annual tumbleweed that is tolerant of heat, drought, and salinity and capable of causing large yield losses in spring wheat (Triticum aestivum L). Increased incidence of glyphosate- and acetolactate synthase (ALS) inhibitor-resistant kochia in western Canada warrants investigation of alternative herbicides to manage these biotypes. Herbicides applied pre- or post-emergence in spring wheat were evaluated based on crop tolerance and control of ALS inhibitor-resistant kochia accessions with and without the glyphosate resistance trait in five environments near Lethbridge and Coalhurst, Alberta, from 2013 to 2015. The most effective and consistent treatments for kochia management included sulfentrazone applied pre-emergence and fluroxypyr/bromoxynil/2,4-D or pyrasulfotole/bromoxynil applied post-emergence. All of these treatments resulted in ≥90% visible control in all environments and ≥90% kochia biomass reduction compared with the untreated control in Lethbridge 2014 and 2015. MCPA/dichlorprop-p/mecoprop-p, dicamba/2,4-D/mecoprop-p, and dicamba/fluroxypyr resulted in acceptable control among environments (≥80% visible control in all environments and ≥80% kochia biomass reduction in Lethbridge 2014 and 2015); however, the latter two options caused unacceptable (>10%) wheat visible injury in Coalhurst 2014. Recent confirmations of auxinic herbicide-resistant kochia in western Canada—due, in part, to use of synthetic auxins to manage glyphosate-resistant kochia in small-grain cereals—will limit kochia management options. When implemented with non-chemical tools as part of an integrated weed management program, alternative herbicide modes of action like protoporphyrinogen oxidase inhibitors before and photosystem II or 4-hydroxyphenylpyruvate dioxygenase inhibitor(s) within spring wheat could mitigate selection for multiple herbicide-resistant kochia.

Dry bean (Phaseolus vulgaris L.), potato (Solanum tuberosum L.), wheat (Triticum aestivum L.), and sugar beet (Beta vulgaris L.) are mainstays of irrigated crop production in southern Alberta. Concerns about soil quality and sustainability instigated a 12 yr (2000–2011) rotation study to compare conventional (CONV) with conservation (CONS) management practices (reduced tillage, narrow-row dry bean, compost addition, and cover cropping). Plant-available water (PAW) was measured using a neutron probe (10–16 count days·season−1, n = 148) on all phases of 4 yr (dry bean–potato–wheat–sugar beet) rotations under CONS and CONV management. A visual monitoring approach was used for irrigation scheduling. For dry bean and sugar beet, management allowable depletion (MAD) was exceeded on only 11%–15% of neutron probe count days over 12 yr. However, MAD was exceeded on 30% of count days for wheat and 43% for potato. Significant crop × management interactions showed that PAW was higher with CONS management most frequently on potato, followed by dry bean, wheat, and sugar beet. This order reflected the prevalence of CONS practices directly impacting each crop. Regression analyses showed that potato, wheat, and sugar beet yield increased significantly as mean growing season water table depth (WTD) increased. This was explained by yield suppression due to excessive soil wetness in seasons with high rainfall and shallow WTD. This study provided comparative soil water dynamics for four major irrigated crops in southern Alberta, over a 12 yr period, which included record high and low growing season precipitation.

Glyphosate-resistant kochia [Bassia scoparia (L.) A.J. Scott], the first known glyphosate-resistant weed in western Canada, was confirmed initially in chemical fallow fields located in Warner County, AB, in 2011. Further selection, lack of control, and rampant spread of this biotype contributed to its increased incidence, now present in about 50% of kochia populations sampled in Alberta. In 2014 and 2015, herbicide mixtures were evaluated based on control of glyphosate-resistant and susceptible kochia in chemical fallow fields near Lethbridge and Coalhurst, AB. The most consistent control (≥80% visual control in all environments with ≥80% biomass reduction in 2014) was observed with glyphosate + dicamba (450 + 580 g a.e.·ha−1), glyphosate + dicamba/diflufenzopyr (450 + 150/50 g a.i./a.e.·ha−1), glyphosate + saflufenacil (450 + 50 g a.i./a.e.·ha−1), and glyphosate + carfentrazone + sulfentrazone (450 + 9 + 105 g a.i./a.e.·ha−1). Reduced efficacy was observed for several herbicide mixtures when they were applied to glyphosate-resistant compared with glyphosate-susceptible kochia accessions. Effective modes of action mixed with glyphosate include synthetic auxins (group 4), a combination of a synthetic auxin and an auxin transport inhibitor (group 19), or protoporphyrinogen oxidase inhibitors (group 14). In response to glyphosate-resistant kochia, many farmers in this region shifted their herbicide programs resulting in greater reliance on synthetic auxins; likely contributing to the recent discovery of auxinic herbicide-resistant kochia biotypes in Alberta in 2017. Careful herbicide stewardship is warranted to mitigate further selection of multiple herbicide-resistant kochia, suggesting an important role for integrated weed management.

Glyphosate (N-(phosphonomethyl)glycine) is broad-spectrum herbicide that is extensively used worldwide, but its effects on the soil microbiome are inconsistent. To provide a sound scientific basis for herbicide re-review and registration decisions, we conducted a four-year (2013-2016) study in which we consecutively applied glyphosate to a wheat (Triticum aestivum L.)-field pea (Pisum sativum L.)-canola (Brassica napus L.)-wheat crop rotation at five sites in the Canadian prairies. The glyphosate rates were 0, 1, 2, 4 and 8 kg ae ha

Plant-based protein is generally preferred for human consumption, while vegetable oil is becoming increasingly popular for industrial uses. It is of importance to evaluate the oil and protein production potential of non-traditional Brassicaceae oilseeds for use as feedstock. In this study, oil and protein contents and their relationship with seed yield were determined for oriental mustard (Brassica juncea L.), canola (Brassica napus L.), camelina (Camelina sativa L.), Ethiopian mustard (Brassica carinata A. Braun), and yellow mustard (Sinapis alba L.) grown across diverse environments. These oilseeds were studied at Lethbridge, Scott, and Swift Current on the Canadian prairie during 2014–2016. Seed oil and protein contents had an inverse relationship with a wide variation among the oilseeds. Oil and protein contents of canola were 48 and 22%, respectively, while S. alba had the lowest oil (29%) but the highest protein (34%) contents. The oil yield (oil concentration by seed mass) was significantly higher in canola (1358 kg ha−1) compared with other oilseeds. Protein yield was in a narrow range with the highest in canola and S. alba (617 and 597 kg ha−1, respectively), and the lowest in camelina (456 kg ha−1). Oil yield was generally higher in site-years with higher precipitation combined with lower temperature during grain filling, whereas protein yield did not have a consistent trend with growing conditions. Considering oil and protein yields across site-years, B. juncea and carinata could be considered as potential alternatives to conventional rapeseed as industrial feedstock sources on the Canadian prairies.

Diversifying cropping systems is essential to enhance oilseed production resiliency in a changing climate. Here, we determined the productivity and stability of five oilseed crops under different crop stubble management strategies over all nine environments. A 2-year cropping sequence study was conducted at nine environ-sites (3 sites×3 independent 2-yr cropping sequence phases). Crops in year 1 consisted of chemical fallow, lentil (Lens culinaris L.) and spring wheat (Triticum aestivum L.), which resulted in fallow, lentil and wheat stubbles for the following year crops. Crops in year 2 were five oilseed crops: canola (Brassica napus L.), Ethiopian mustard (Brassica carinata L.), oriental mustard (Brassica juncea L.), yellow mustard (Sinapis alba L.), and camelina (Camelina sativa L.). Over all nine environ-sites, B. juncea had high yield and low yield variation, making it a good substitute for B. napus, the primary oilseed crop in acreage on the Canadian Prairies. Lentil and wheat stubbles reduced oilseed crop yields by 4% and 5% compared with chemical fallow, respectively; however, at the 2-yr cropping sequence level, lentil-oilseed sequence increased system production, expressed by annualized canola equivalent yield, by 33% compared with wheat–oilseed sequence and by 112% compared with fallow–oilseed system. The lentil-oilseed sequence had the lowest variation in production and was most suitable for high-yielding environments compared with fallow- and wheat–oilseed sequences, while B. juncea- and B. napus-based cropping sequences were most stable based on the static and dynamic stabilities among all five oilseed-based cropping sequences. Crops explained more variation in system production than weather (40% vs 5%) because of a dramatic difference of cropping sequences with and without fallow. Under changing climatic conditions, diversifying conventional wheat- or fallow-based canola systems using lentil and B. juncea will enhance system productivity and yield stability across different environments.

Enhancing the stability of crop production is vital for agriculture under climate uncertainty. Conventional fallow and shallow-rooting pulse crops such as lentil (Lens culinaris Medic.) have been incorporated in oilseed-cereal cropping systems to cope with dry conditions on the semiarid Canadian prairies. However, the static and dynamic stability of these adaptation practices at a cropping system level is unclear due to the complexity of interactions. This study assessed the effects of diversified rotation systems as drought adaptation practices on the productivity and stability of oilseed-cereal cropping systems. Nine 3-year crop rotations were tested for two cycles at three sites from 2013 to 2016. The 3-year crop sequences included fallow, lentil, and spring wheat (Triticum aestivum L.) in rotation phase 1, followed by canola (Brassica napus L.), oriental mustard (Brassica juncea L.), and camelina (Camelina sativa L. Crantz) in phase 2, and the rotation phase 3 was durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) in all nine rotation systems. On average, the lentil system increased system productivity, expressed by annualized durum wheat equivalent yield, by 24% and 78% compared with the spring wheat and fallow systems, respectively. Stability analysis revealed that the lentil – B. juncea – durum wheat and lentil – B. napus – durum wheat systems had the least variation across the environments and were well adapted to high-yielding sites. The fully-phased rotations across various environments showed that the drought-induced reductions in system productivity ranged from 3 to 47% compared with yields under normal weather, with the lentil – oilseed – durum systems having least reduction. Quantitative assessments revealed that about 36% of the variation in system productivity was associated with rotation systems and additional 30% was due to weather-related factors. In conclusion, the inclusion of lentil in rotation increases systems productivity and reduces yield variation in oilseed-cereal cropping systems in changing environments.

With the increasing resistance of wild oat (Avena fatua L.) to herbicides, there is a need to evaluate the potential of alternative cropping systems based on integrated weed management principles. A 5-yr field study at eight sites across Canada was used to evaluate the profitability of alternative cropping systems that have the potential to control wild oat using cultural practices in conjunction with herbicides. Cultural practices included twice the recommended seeding rates, fall-seeded winter crops, barley (Hordeum vulgare L.) silage, fallow, and alfalfa (Medicago sativa L.). Seven of the 14 cropping systems in this study did not include wild oat herbicide for three consecutive years, controlling wild oat entirely by cultural practices. Cropping system profitability varied by location. For many locations, combinations of barley silage and fall-seeded winter crops without wild oat herbicide application were as profitable as a system of canola (Brassica napus L.) and wheat (Triticum aestivum L.) with wild oat herbicide applied every year. Unprofitable systems generally included those with fallow, alfalfa, and fall-seeded winter crops in regions with rates of high winter kill. Wild oat control can be achieved with diverse cropping systems that are as profitable as conventional annual cropping that relies on herbicide control of wild oat.

Relating soil microbial properties to crop productivity is important to appreciate the value of soil microbial activities in sustainable agriculture. Over a 10-year period, we evaluated the effects of conservation (CONS) management practices on soil microbial biomass carbon (MBC). The CONS practices included addition of composted cattle manure; reduced tillage; diverse crop rotations that comprised wheat (Triticum aestivum L.), potato (Solanum tuberosum L.), dry bean (Phaseolus vulgaris L.), and sugar beet (Beta vulgaris L.); and use of cover crops. The CONS management was applied to 3- to 5-year irrigated crop rotations and compared with conventional (CONV) management systems that did not have any of the CONS practices. Continuous wheat was also included. We then related MBC to wheat yields. Averaged over the 10-year period, CONS management overall increased MBC in wheat rhizosphere and bulk soil by 18% and 34%, respectively. When rotations of the same length were compared, CONS management in 3-year rotations increased rhizosphere MBC by 18% and bulk soil MBC by 30%; the corresponding increases in 4-year rotations were 13% and 36%. Regressions between soil MBC and wheat yields were quadratic, with MBC in wheat rhizosphere associated with increasing wheat yields up to 720 mg C kg soil. The corresponding value for MBC in bulk soil was 645 mg C kg soil. These effects were related to the compost and crop C inputs to the soil, which impacted soil organic C contents. Therefore, CONS management resulted in a cycle of high MBC and high wheat yields.

Potato and sugar beet, which are widely grown in southern Alberta, may degrade soil quality because they return little C to the soil, and their harvesting methods cause soil disturbance that increases erosion risk. To reverse these effects, a 12-yr study was established to evaluate soil conservation (CONS) management systems for rotations that included potato, sugar beet, dry bean and wheat. These systems, comprising addition of feedlot manure compost, reduced tillage, diverse crop rotations and use of cover crops, were applied to 3- to 5-yr crop rotations. They were compared with conventional (CONV) management systems that did not have any of the CONS practices. In the final year of the study, pyrosequencing was used to determine differences in soil bacterial community profiles between the two systems (CONS vs. CONV) in wheat rhizosphere and bulk soil. Thirteen phyla were observed, and the most abundant were Proteobacteria (39.6%), Actinobacteria (19.1%) and Acidobacteria (14.9%). Soil bacterial α-diversity increased under CONS relative to CONV management. However, whereas the relative abundances of Bacteroidetes and Firmicutes were greater under CONS than CONV management, the reverse was observed for Acidobacteria and Gemmatimonadetes. Proteobacteria were also more abundant under CONS than CONV management, but only in bulk soil. The community structures of the bacterial communities were in agreement with the differences in relative abundances. These differences were consistent with the ecological classification of soil bacteria as copiotrophic or oligotrophic. Therefore, CONS management systems altered the soil bacterial community profiles and increased the productivity of these soils.

The increasing acreages of crops like potato and sugar beet, which return little C to the soil, and whose harvesting methods cause soil disturbance, led to the establishment of a 12-yr study to evaluate soil conservation (CONS) management systems in southern Alberta. The CONS management systems, applied to 3- to 6-yr crop rotations, were compared with conventional (CONV) management systems that included wheat monoculture. The CONS management was a suite of practices that included addition of cattle manure compost, reduced tillage, diverse crop rotations and use of cover crops that CONV management did not have. In the last two years of the study (2010 and 2011), soil microbial biomass was measured in bulk soil and wheat rhizosphere using the substrate-induced respiration method and phospholipid fatty acid (PLFA) biomarkers. β-glucosidase enzyme activity was measured to evaluate soil functioning (C cycling). Total soil microbial biomass, and that of its components (fungi and bacteria), was significantly greater under CONS management than under CONV management. The total PLFA contents of 3- and 4-yr CONS rotations (15.24–34.69 nmol g −1 soil) were 84–193% greater than those in CONV management (33.45–63.66 nmol g −1 soil) when differences were significant, and fungal PLFA was up to 382% greater. β-glucosidase activity was 50% greater under CONS management than CONV management. Principal component analysis confirmed that the soil microbial community structures in the different rotations were shaped by management practices. These positive responses of soil microbial communities to conservation management will enhance biological processes including nutrient cycling and biological pest control.

Soil surface cover (crop residue and fall-seeded cover crops) during the nongrowing season is an important tenet of sustainable agriculture, reducing wind and water erosion risk and enhancing soil water conservation. Expansion of irrigated row crop production, namely, potato (Solanum tuberosum L.), dry bean (Phaseolus vulgaris L.), and sugar beet (Beta vulgaris L.), in southern Alberta in the late 1990s prompted a 12-year (2000 to 2011) study to evaluate rotations and soil management systems for improved soil quality. The study compared conservation (CONS) and conventional (CONV) management systems in three- to six-year rotations. Conservation management included cover crops; reduced tillage; feedlot manure compost addition; and solid-seeded, narrow-row dry bean production. Beginning in the third year of the study (2002), surface residue cover was estimated each spring prior to tillage or seeding. Averaged over 10 years (2002 to 2011), residue cover was significantly higher on CONS (15.6%) versus CONV (7.1%) management. Cover was significantly higher where wheat (Triticum aestivum L.) was the previous crop (33.7%) compared to narrow-row dry bean (9.7%), which was significantly higher than potato and sugar beet (6.5% to 6.7%), which were in turn significantly higher than wide-row bean (3.6%). Inclusion of a fall rye (Secale cereale L.) cover crop after potato or dry bean increased residue cover close to or more than 30%, the threshold required to reduce wind erosion risk. Long-term replacement of cereals with lower residue-producing crops (e.g., potato, dry bean, and sugar beet) on irrigated rotations in southern Alberta should be considered judiciously in light of potential negative effects on surface residue cover.

A 12-yr. (2000–2011) study was conducted in Alberta, Canada to compare the energy use efficiency (EUE) of conventional (CONV) and conservation (CONS) potato (Solanum tuberosum L.) management practices. Potato was grown in 3- to 6-yr. rotations which included dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), soft wheat (Triticum aestivum L.), oat (Avena sativa L.), and timothy (Phleum pratense L.). CONS included compost application, reduced tillage, cover crops, and solid-seeded bean. Findings suggested that potato in 5-yr. CONS produced the highest EUE compared to the other CONS or CONV rotations. CONS can be used as a means of reducing the reliance on non-renewable energy inputs and improving overall EUE of potato production when less than 21% of the N content of compost applied was counted toward energy input use of potato production. At more than 21%, potato in the 4-yr. CONV became more favorable compared to potato in other rotations.

The tripling of glyphosate use in the Canadian prairies during the past decade has raised concerns over the possible accumulation of glyphosate and its main metabolite AMPA in soil over time and whether there could be any detrimental effects on crop production. A controlled environment study was conducted at two locations in Alberta, Canada, to determine glyphosate and AMPA soil concentrations that would injure wheat, field pea, and canola. Treatments included glyphosate acid or AMPA applied at 0, 10, 25, 100, 250, and 500 mg kg−1soil. Shoot and root biomass determinations 8 wk after emergence (WAE) indicated that shoot and root biomass of all crops progressively declined with increasing soil concentrations of glyphosate at both locations. In contrast, AMPA reduced crop shoot and root biomass at only one of two sites. Estimated soil concentrations of glyphosate causing 20% reductions in shoot and root biomass ranged from 80 to 190, 90 to 350, and 120 to 320 mg kg−1for field pea, canola, and wheat, respectively. Soil concentrations of AMPA causing 20% crop biomass reductions ranged from 40 to 70, 20 to 30, and 80 to 120 mg kg−1for field pea, canola, and wheat, respectively. Although substantial crop injury occurred in this study, it must be noted that these rates are very high in terms of field application rates that would be required to achieve these soil concentrations. Doses causing crop injury would convert to estimated glyphosate field rates ranging from 17.6 to 77 kg ha−1. Overall results indicate that even with frequent high-dose glyphosate applications over several years, the likelihood of wheat, field pea, and canola injury from soil residues is low. Nevertheless, there may be merit in greater monitoring of glyphosate and AMPA soil residues in cropping systems with high glyphosate utilization over a long time period.

Efficient natural dispersal of herbicide-resistance alleles via seed and pollen can markedly accelerate the incidence of herbicide-resistant weed populations across an agroecoregion. Studies were conducted in western Canada in 2014 and 2015 to investigate pollen- and seed-mediated gene flow in kochia. Pollen-mediated gene flow (PMGF) from glyphosate-resistant (GR) to non-GR kochia was quantified in a field trial (hub and spoke design) at Saskatoon, Saskatchewan. Seed-mediated gene flow of acetolactate synthase (ALS) inhibitor-resistant kochia as a function of tumbleweed speed and distance was estimated in cereal stubble fields at Lethbridge, Alberta and Scott, Saskatchewan. Regression analysis indicated that outcrossing from GR to adjacent non-GR kochia ranged from 5.3 to 7.5%, declining exponentially to 0.1 to 0.4% at 96 m distance. However, PMGF was significantly influenced by prevailing wind direction during pollination (maximum of 11 to 17% outcrossing down-wind). Seed dropped by tumbleweeds varied with distance and plant speed, approaching 90% or more (ca. 100,000 seeds or more) at distances of up to 1,000 m and plant speeds of up to 300 cm s–1. This study highlights the efficient proximal (pollen) and distal (seed) gene movement of this important GR weed.

Sugar beet (Beta vulgaris L.) has a long history as an option for irrigated crop rotations in southern Alberta. A 12-yr (2000–2011) study compared conservation (CONS) and conventional (CONV) management for sugar beet in 4- to 6-yr rotations which also included dry bean (Phaseolus vulgaris L.), potato (Solanum tuberosum L.), and soft white spring wheat (Triticum aestivum L.). Oat (Avena sativa L.) and timothy (Phleum pratense L.) were included in the longest 6-yr rotation. Conservation management incorporated reduced tillage, cover crops, feedlot manure compost addition, and solid-seeded dry bean. Compared with a 4-yr CONV rotation (52.2 Mg ha−1), sugar beet root yield (averaged over the second 6 yr of the study, 2006–2011) was significantly higher, by 11%, on 4- and 5-yr CONS rotations (57.7–57.9 Mg ha−1), and by 8% on a 6-yr CONS rotation (56.1 Mg ha−1). Sugar beet impurity parameters were significantly affected by rotation in, at most, 3 of 12 yr. However, averaged over the final 6 yr of the study (2006–2011), a significantly higher K concentration (impurity) was found with CONS (2108 mg kg−1) vs. CONV (1958 mg kg−1) management. Integrating CONS management practices into sugar beet rotations led to significant yield benefits while effects on sugar beet quality were minimal.

Low-tillage systems are needed to improve soil conservation in organic farming. This study evaluated three no-till/low-till cover crop termination strategies on the basis of weeds, N dynamics and growth and yield of a wheat (Triticum aestivum L.) test crop. Field experiments were conducted in two different Canadian provinces. The blade roller, flail mower, and undercutter cultivator were comparable with standard tillage for controlling a full-season barley (Hordeum vulgare L.)–pea (Pisum sativum L.) cover crop. Reduced tillage implements resulted in some depression of soil temperature the following spring and some delay in spring wheat development. Yield differences between treatments were related to weed and N consequences not seedbed quality or wheat development. Undercutting sometimes resulted in better perennial weed control than blade rolling. Blade roll plus late-season tillage treatment improved perennial weed control but provides less residue for soil protection. Flail mowing resulted in more rapid cover crop biomass mulch decomposition, allowing weeds to establish. Reducing tillage reduced N availability to the following wheat crop relative to tillage, and reduced N leaching. Poor weed suppression in low-till treatments meant that a higher proportion of available N was sometimes captured by weeds compared with the wheat crop. Future studies should test combinations of alternative tillage and crop termination approaches aimed at specific weed and nutrient challenges.

Previous research has demonstrated that late and sequential applications of glyphosate and glufosinate can have adverse effects on glyphosate- and glufosinate-resistant canola. Similarly, imidazolinone (IMI)-resistant canola may be affected negatively by late applications of imidazolinone herbicides. Field trials were established across the Northern Great Plains region from 2010 to 2012 to examine the response of IMI-resistant canola yield, yield components, and seed quality to late and sequential applications of imazamox. Plots received either a single imazamox application at the two-leaf, six-leaf, bolt, or early bloom stages or sequential applications at the two-leaf followed by six-leaf, two-leaf followed by bolting, and two-leaf followed by early bloom stages; an unsprayed control was included for comparisons. Results indicated that in most site-years there was no effect of imazamox application timing on IMI-resistant canola yield, yield components, or seed quality. These results suggest that late and sequential applications of imazamox to IMI-resistant canola should have little effect on canola production, even if they are made beyond the recommended six-leaf stage. In situations where growers are forced to make late applications (beyond six leaves) to IMI-resistant canola, using solely imazamox appears to minimize adverse effects on seed yield and quality.

Past agronomic practices, particularly cropping sequence and the balance between N applications and crop N removal, will influence soil N supply and crop yield potential. Nitrogen (N) fertilizer applications required to optimize crop yield and quality will be a function of the difference between crop N demand and the amount of N supplied by the soil. Therefore, assessment of the effect of past management practices on crop yield potential and soil N dynamics is important to accurately predict crop fertilizer N requirements. Field studies were conducted at seven locations representative of the varying soil types and ecozones across the Canadian prairies to determine the persistence of the effects of legume and non-legume crops and repeated N fertilizer applications on soil N supply and on the yield and N uptake of spring wheat ( Triticum aestivum L.) and canola ( Brassica napus L.) for two seasons after fertilization had ceased, corresponding to the fourth and fifth season after legume crop production. Field pea ( Pisum sativum L.), lentil ( Lens culinaris Medik.), faba bean ( Vicia faba L.), canola and wheat harvested for grain, and faba bean grown as a green manure were direct-seeded in 2009. Canola was seeded in 2010, barley ( Hordeum vulgare L.) in 2011, and canola again in 2012 with fertilizer N applied at 0, 30, 60, 90 and 120 kg ha −1 in each crop. Fertilizer N applications were then halted and spring wheat was grown in 2013 and canola in 2014, without fertilizer N applications. Very few effects of crops grown in 2009 were apparent on soil NO 3 -N supply, crop yield or crop N accumulation by 2013, which was the fourth year after crop growth, and no effects were observed in 2014. In contrast, fertilizer N applied from 2010 to 2012 had persistent effects, increasing soil NO 3 -N concentration, crop yield and crop N accumulation for two growing seasons after fertilization had ceased, although the magnitude of response varied considerably with location. By fall of 2014, effects of preceding fertilizer applications on soil NO 3 -N were no longer significant. Accumulation of N in wheat grain and straw was closely related (R 2 = 0.86) to soil NO 3 -N across locations while the relationship between soil NO 3 -N and N accumulation in canola seed was not as strong (R 2 = 0.60). Therefore, measurement of soil nitrate is a valuable tool for producers in this region to use when selecting fertilizer N application rates, but mineralization of N over the growing season will also contribute to crop N uptake. Residual effects of N fertilization can be substantial under prairie conditions, increasing N supply to crops for up to two years after the final application, and should be taken into account when assessing fertilizer use efficiency and N requirements for crop production.

Conventional (CONV) potato (Solanum tuberosum L.) production in Alberta has relied on high levels of soil disturbance which may result in long-term degradation of soil resources. A 12-yr (2000–2011) study was conducted to address issues with the CONV system and to evaluate the effects of conservation (CONS) practices on the economics of irrigated potato production. Potato was grown in 3- to 6-yr rotations which included dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), soft wheat (Triticum aestivum L.), oat (Avena sativa L.), and timothy (Phleum pratense L.). CONS included reduced tillage, cover crops, compost addition, and solid-seeded bean. Averaged over 12-yr, potato yields for 4-yr CONV rotations (potato–wheat–beet–bean) were lower than those for CONS systems. However, the decreased costs associated with not using compost in 4-yr CONV offset the losses in yield, thereby resulting in an overall net income higher than that of CONS systems.

Crop rotation and nitrogen (N) fertilization can influence soil N cycling, however, less is known about their interactive effects under varying soil and climatic conditions. We examined the interactive effects of preceding crops and N fertilizer rates on soil N cycling in canola (Brassica napus L.) and spring wheat (Triticum aestivum L.) cropping systems in no-till soils in the Canadian prairies. Field pea (Pisum sativum L.), lentil (Lens culinaris Medik), faba bean (Vicia faba L.; faba bean-seed), canola and wheat grown for grain, and faba bean green manure (faba bean-GRM) were the preceding crops and were direct-seeded at 7 and 6 locations in 2009 and 2010, respectively. Canola and wheat were seeded in 2010 and 2011 (2012 for wheat at one site), respectively with N fertilizer applied at 0, 30, 60, 90 and 120 kg N ha−1. Above-ground residue N returned was greatest for faba bean-GRM and lowest for canola and wheat. On average across sites, apparent in-crop N mineralization (ANM) under canola was greater following faba bean-GRM than all other preceding crops, except field pea, while under wheat, ANM was greater following all the legumes than following canola and wheat. Crop N uptake increased with N fertilizer rate, but the response was generally lower following faba bean-GRM and lentil. The N budget showed that 40–65% of crop N uptake (35–100% at highest ANM site) was possibly derived from ANM, more so following legumes, as compared to 35–60% from N fertilizer. The surplus and unaccounted N were particularly pronounced when canola and wheat were preceded by legumes rather than by canola or wheat. Our findings indicate that legumes can enhance soil N supply in no-till soils, and also highlight the importance of adjusting N fertilizer rates based on preceding crops to minimize the potential for N losses.

In western Canada, more money is spent on wild oat herbicides than on any other weed species, and wild oat resistance to herbicides is the most widespread resistance issue. A direct-seeded field experiment was conducted from 2010 to 2014 at eight Canadian sites to determine crop life cycle, crop species, crop seeding rate, crop usage, and herbicide rate combination effects on wild oat management and canola yield. Combining 2× seeding rates of early-cut barley silage with 2× seeding rates of winter cereals and excluding wild oat herbicides for 3 of 5 yr (2011 to 2013) often led to similar wild oat density, aboveground wild oat biomass, wild oat seed density in the soil, and canola yield as a repeated canola–wheat rotation under a full wild oat herbicide rate regime. Wild oat was similarly well managed after 3 yr of perennial alfalfa without wild oat herbicides. Forgoing wild oat herbicides in only 2 of 5 yr from exclusively summer annual crop rotations resulted in higher wild oat density, biomass, and seed banks. Management systems that effectively combine diverse and optimal cultural practices against weeds, and limit herbicide use, reduce selection pressure for weed resistance to herbicides and prolong the utility of threatened herbicide tools.

We investigated the effect of environmentally smart nitrogen (ESN) fertilizer on nitrous oxide (N2O) emissions under no-till barley (Hordeum vulgare L.) production over 3 years at three sites in Alberta, Canada. Treatments included two barley cultivars, with ESN and urea applied at 1× and 1.5× the recommended rate, and herbicide at 50% and 100% of registered in-crop rates. Cumulative N2O emissions over the growing season were low (0.11 to 1.32 kg nitrogen (N) per hectare or 0.05–0.22 g N kg−1 grain yield), and not affected by barley cultivars or herbicide rates in all nine site-years, nor by fertilizer type or rate in seven out of nine site-years. However, average N2O emissions from ESN were 15% lower (P = 0.05) than urea across all site-years. Our results suggest ESN could play a role in reducing N2O emissions, but the reduction will depend on rainfall events and crop N utilization.

This study evaluated the effects of a ferulic acid esterase (FAE) and a non-FAE-producing inoculant applied alone or in combination with exogenous fibrolytic enzymes (EFE) on the fermentation and nutritive value of mixed grain (barley, oats and spring triticale) silage. The mixed crop was ensiled in laboratory mini-silos either untreated (CON), or treated with a FAE inoculant (FAE), a non-FAE inoculant (NFAE) or NFAE + EFE. Inoculated silages were lower (P

Potato, dry bean, and sugar beet production have increased markedly in recent years on irrigated cropland in Alberta, Canada. Concerns exist about declining soil quality and increased soil erosion when these low-residue crops are grown in sequence in short-duration rotations. A 12-yr rotation study was conducted to determine the merits of adopting various conservation practices (reduced tillage, cover crops, composted manure) and longer-duration rotations to develop a more sustainable production system for these row crops. This article reports on weed density and weed seedbank data collected in the study. Weed densities recorded prior to applying postemergence herbicides indicated that conservation compared with conventional management treatments had greater weed densities in 30 to 45% of the cases in 3-, 4-, and 5-yr rotations. In contrast, a 6-yr conservation rotation that included 2 yr of timothy forage resulted in similar or lower weed densities than rotations with conventional management practices. Residual weed densities recorded 4 wk after applying postemergence herbicides were only greater in conservation than conventional rotations in 2 of 12 yr, regardless of rotation length. Weed seedbank densities at the conclusion of the 12-yr study were similar for 3- to 6-yr rotations under either conservation or conventional management. These findings indicate that implementing a suite of conservation practices poses little risk of increased weed populations in the long term. This knowledge will facilitate grower adoption of more sustainable agronomic practices for irrigated row crops in this region.

The development of glyphosate-resistant canola has provided improved weed-management options for growers, but crop tolerance to glyphosate may be inadequate at later growth stages. In this study, glyphosate-resistant canola 45H28 (RR) was used to determine the effects of glyphosate application timing on yield and yield components at several sites in western Canada. Canola received a single glyphosate applications at the two-leaf, six-leaf, bolting, and early bloom stages and sequential applications at the two-leaf + six-leaf, two-leaf + bolting, and two-leaf + early bloom stages. Contrasts were made between early vs. late, single vs. sequential, and on-label (two to six-leaf stage) vs. off-label (above six-leaf stage). In general, differences between application timings were observed for yield and yield components in 3 of 8 site-yr. Off-label applications of glyphosate (later than six-leaf) significantly decreased yield, seeds per pod, and increased thousand-seed weight and aborted pods in canola at the Lethbridge and St. Albert locations. Increased glyphosate translocation because of adequate, but not excessive, moisture to new growth may have suppressed new seed formation and encouraged pod abortion at the time of application in the 2010 and 2011 seasons. Results from this experiment demonstrate the importance of proper application timing of glyphosate on canola and can help better predict the effects of late applications.

Irrigated processing potato production is an important part of southern Alberta’s agricultural economy. A 12-year (2000–11) study compared conservation (CONS) and conventional (CONV) management for potato in 3- to 6-year rotations which also included dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), and soft wheat (Triticum aestivum L.). Oat (Avena sativa L.) and timothy (Phleum pratense L.) were added to the longest rotation. Conservation management included reduced tillage, cover crops, feedlot manure compost addition, and solid-seeded dry bean. Averaged over 12 years, a 5-year CONS rotation (potato–wheat–sugar beet–wheat–dry bean) resulted in 18 % higher marketable tuber yield than a 3-year CONV rotation (potato–dry bean–wheat). Reduced incidence of potato early dying was also found with CONS management. Results indicate that integration of CONS management practices led to yield and disease control benefits without negatively impacting tuber quality.

Inclusion of legumes in crop rotations is a sustainable approach to reducing nitrogen (N) fertilizer requirements and increasing subsequent crop yields. However, the magnitude of the benefit will depend on the specific legume, the subsequent crop and site-specific conditions. This study compared the effects of preceding legumes and non-legumes on yields and economic optimum N rates (EONR) in a Hard Red Spring wheat (Triticum aestivum L.)–hybrid canola (Brassica napus L.) cropping sequence. Field pea (Pisum sativum L.), lentil (Lens culinaris Medik), faba bean (Vicia faba L.; faba bean-seed), canola and wheat grown for grain, and faba bean grown as green manure (faba bean-GRM) were the preceding crops and were direct-seeded at six locations in western Canada in 2010. Wheat was seeded in 2011 and canola in 2012, with N fertilizer applied at 0, 30, 60, 90 and 120 kg N ha−1 in each year. Averaged across preceding crops, N application increased crop yields at all sites. Wheat grain yield was greater, with a corresponding lower EONR, following legumes than non-legumes due in part to increased N availability. Greater non-N benefits to wheat following legumes than non-legumes were also evident at all but one site, with non-N benefits being lowest for preceding wheat. While preceding legumes had no effect on canola seed yield across sites, EONR for canola were >50% lower for legume-wheat than non-legume-wheat rotations. Among the legumes, growing faba bean-GRM, field pea and lentil were most likely to increase crop yields and reduce EONR as compared to faba bean-seed. Overall, growing legumes for seed before a wheat–canola cropping sequence in conventional cereal cropping systems can increase crop yields, reduce EONR and improve the long-term sustainability of cereal cropping systems.

Rapid expansion of irrigated row crop production, viz., potato (Solanum tuberosum L.), dry bean (Phaseolus vulgaris L.), and sugar beet (Beta vulgaris L.), in southern Alberta in the late 1990s provided the impetus for a 12-yr (2000–2011) study to evaluate cropping systems that maintained or improved soil quality. The study compared conservation (CONS) and conventional (CONV) management in rotations of 3- to 6-yr duration. Conservation management included reduced tillage, cover crops, feedlot manure compost addition, and solid-seeded narrow-row dry bean production. After 12 yr, particulate organic matter C (POM-C) and N (POM-N) showed >145% increases (POM-C, 2.2–5.8 Mg ha⁻¹; POM-N, 0.20–0.49 Mg ha⁻¹) with CONS management compared with 45 to 50% increases in total organic C and N (TOC, 10.2–15.3 Mg ha⁻¹; TN, 1.06–1.53 Mg ha⁻¹) and 20% increases in fine organic matter (FOM)-C and -N (FOM-C, 8.3–10.1 Mg ha⁻¹; FOM-N, 0.87–1.04 Mg ha⁻¹). Aggregate stability of the pre-wet >1-mm fraction increased significantly from 13% under CONV to 21% under CONS management. Overall, the 5-yr CONS rotation (sugar beet–wheat (Triticum aestivum L.)–dry bean–potato–wheat) ranked highest for soil quality (100%), with CONV rotations substantially lower (33–38%). Adoption of CONS management enhanced a wide range of soil quality attributes that could safeguard sustainable expansion of irrigated specialty cropping in southern Alberta.

Winter cereals provide distinct advantages over spring cereals. This includes higher grain yields and limiting weed pressure, soil erosion, and exposure to diseases and insect pests, which are regularly serious threats to spring cereals. The agronomic system for winter cereals in western Canada is built around ensuring that the crop survives winter. Critical to this system is uniform plant stands reaching an optimum growth stage to maximize cold tolerance and no-till production systems that maintain insulating snow cover through the use of stubble from a previous crop. Breeding has led to significant increases in grain yield for both winter wheat and fall rye, however, no progress in cold tolerance improvement has been realized by winter cereal plant breeders over the same period. Progress in fall rye breeding has led to more recent varieties having reduced lodging and plant height and increased seed size and test weight. For winter wheat, the incorporation of robust disease resistance packages ensures ad...

The annual global economic loss caused by weeds has been estimated at more than $100 billion U.S. dollars (Appleby et al. 2000). Additionally, worldwide annual herbicide sales are in the range of U.S. $25 billion (Agrow 2003). In light of these large dollar figures, it becomes clear that a greater understanding of crop—weed interactions is essential in order to develop cost-effective and sustainable weed management practices.

Soil microorganisms mediate many important biological processes for sustainable agriculture. However, correlations between soil microbial properties and crop productivity cannot always be demonstrated. We collected soil microbial data from a canola ( Brassica napus L.) study that was conducted at seven sites on the Canadian prairies about agricultural practices focused on increasing canola yields. The treatments consisted of two canola seeding rates (75 or 150 seeds m −2 ), two nitrogen rates (1× and 1.5× soil test recommendation) and three nitrogen form–fungicide (prothioconazole) combinations (uncoated urea, no fungicide; uncoated urea + fungicide; and 50% polymer-coated urea + fungicide) in a 2 × 2 × 3 factorial arrangement. Microbial biomass C (MBC), β-glucosidase enzyme activity and functional bacterial diversity (based on C substrate utilization patterns) were determined in canola rhizosphere and in bulk soil and related to canola yields. The effects of seeding rate, nitrogen (N) rate and N form on soil microbial biomass, enzyme activity or bacterial functional diversity were usually not statistically significant. In the few cases where significance occurred, doubling the seeding rate from 75 to 150 seeds m −2 usually increased these microbial properties in canola rhizosphere or bulk soil. Increasing N rate to 1.5× the recommended rate had mostly positive effects in canola rhizosphere and negative effects in bulk soil. The effects of N form (including addition of fungicide) were inconsistent. Soil MBC and β-glucosidase enzyme activity correlated positively with canola grain yield at the five sites where yields were −1 ( r = 0.51** to 0.76**), but no or weak negative correlations were observed at the two sites with yields >4000 kg ha −1 . The functional diversity of soil bacteria was not or was weakly negatively correlated with grain yields. Some of these relationships appeared to be influenced by canola root maggot damage because root damage was usually negatively correlated with the soil microbial characteristics, but the correlations were too weak to be relevant. These results suggest underground feedback interactions between crops and soil microbes, i.e., crop/soil management practices that enhance crop growth also enhance soil microbial communities and their activities, and vice versa.

The ability of forage crops to out-compete foxtail barley (Hordeum jubatum L.) and downy brome (Bromus tectorum L.) weeds often fails in saline soils. Ten forage treatments [alfalfa (Medicago sativ...

Historically, soft white spring (SWS) wheat (Triticum aestivum L.) has been a crop choice in southern Alberta’s irrigation districts. A 12-yr (2000–2011) study compared conservation (CONS) and conventional (CONV) management for SWS wheat in 3–5-yr rotations with dry bean (Phaseolus vulgaris L.), potato (Solanum tuberosum L.), and sugar beet (Beta vulgaris L.). Conservation management incorporated reduced tillage, compost, cover crops, and narrow-row dry bean. Wheat was largely unresponsive to CONS management, with only 2 of 13 parameters showing significant positive effects: greater grain Ca (605 vs. 576 μg g−1 on CONV) and S concentrations (1137 vs. 1105 μg g−1 on CONV). Two parameters showed significant negative responses to CONS management: shorter plant height (82.8 vs. 84.8 cm on CONV) and higher take-all [Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker] severity (1.34 vs. 1.27 rating on CONV). The remaining nine parameters were unresponsive: plant density, days to maturity, grain y...

The efficacy of harvest weed seed control depends on the extent of seed shatter of the targeted weeds. Seed shatter of nine weed species, namely, wild oat (Avena fatua L.), green foxtail [Setaria v...