Combining low‐input systems with conservation tillage may be feasible for field crops under northeastern conditions. This study compared the effects of herbicide‐free (HF), organic (ORG), ...conventional (CONV), and herbicide‐tolerant (GM) cropping systems applied to three 20 yr‐old tillage treatments (MP, moldboard plow; CP, chisel plow; NT, no‐till) on weed biomass and crop productivity in a 4‐yr barley (Hordeum vulgare L.)–red clover (Trifolium pratense L.)–corn (Zea mays L.)–soybean Glycine max (L.) Merr. rotation. Barley yield (4.5 Mg ha–1), and red clover forage yield (two cuts: 5.3 Mg ha–1) were similar across treatments. With MP and CP tillage, silage corn yield for CONV and GM systems (15 Mg ha–1) was 25% greater than for HF and ORG (11 Mg ha–1), whereas HF‐NT and ORG‐NT systems produced no harvestable yield. Soybean yield for HF‐MP and ORG‐MP systems was similar to that for CONV and GM (2.4 Mg ha–1), whereas yield in for the HF and ORG systems with CP and NT was half or less than for other treatments. Some form of primary tillage (CP or MP) was needed in corn and soybean to achieve adequate weed control and yield in the ORG and HF systems. Midseason weed proportion of total biomass was greater in the HF and ORG systems with CP and NT, and provided good yield prediction in corn (R2 = 0.74) and soybean (R2 = 0.84). Nutrient availability appeared adequate in corn following N2–fixing red clover but limiting in NT and CP for soybean following corn. Improving crop sequence, fertilization, and weed management will be key to the adoption of low‐input systems using conservation tillage practices in cool, humid climates.
Environmentally Smart Nitrogen (ESN) (Agrium, Calgary, AB) is a polymer‐coated form of urea N that provides controlled‐release, allowing higher seed‐placed safe rates. Field studies were conducted ...from 2009 to 2012 near Lethbridge, AB, Canada, to determine how upper limits of seed safety using seed‐placed ESN in cereals and canola change with increased N rates and alterations to the coating integrity of ESN. Alterations to the coating integrity of ESN were created in the laboratory (consistent within an incremental range of 20 to 80% N release after 7 d immersion in 23°C water) and then arranged in a factorial combination with five rates (30, 45, 60, 75, and 90 kg N ha−1) of the seed‐placed ESN lots and urea (100% N release). Low N release rates (20–40%) were important for all three crops and increased the safe rate of seed‐placed ESN to the optimum range of 60 to 90 kg N ha−1 for spring cereals and 60 kg N ha−1 for canola. This confirms three times the safe rate of urea (observed at 30 kg N ha−1 for cereals) can be seed‐placed and achieve N sufficiency for spring wheat in one operation. Canola stand establishment was negatively affected by greater N release and rates. However, reductions to canola yield were modest (5%) unless ESN was replaced with urea, which reflects its greater compensatory response to stand thinning. Results from this study confirm the substitution of urea with ESN allows 3× rates of seed‐placed N provided N release was ≤40%, which is readily achieved through proper handling.
Grazing swathed, small-grain crops can reduce costs of overwintering beef cows (Bos taurus) by 40%. However, the late planting required to target mid-September harvest may be associated with low ...yield and carrying capacity. The objective was to compare whole-plant yield, nutritive value, and potential carrying capacity in relation to beef cow requirements for spring barley (Hordeum vulgare L.), oat (Avena sativa L.), and triticale (X Triticosecale Wittmack) when planted on seven weekly intervals (10 May-23 June) over 3 yr at Lacombe, AB; whole-plant material was harvested at soft dough (barley and triticale) or milk stages (oat). Data were analyzed relative to planting date delay as an independent variable. Barley matured more rapidly than oat and triticale, with the latest planting date harvested on 27 August for barley, 8 September for oat and 25 September for triticale. Nutritive value for barley and triticale was unaffected by planting date, but neutral (NDF) and acid detergent fiber (ADF) concentrations increased quadratically with delay in planting for oat. In vitro true digestibility (IVTD) was lower for oat than barley and triticale. Yield declined linearly with planting delay for barley (35-39%), but increased (quadratically) as planting was delayed from late May to early June for oat (8%) and triticale (10%). Consequently, the potential carrying capacity for triticale was 1.6 and 1.8 times greater than barley and oat, respectively when planted for swathing in late August or early September.
As chemical management options for weeds become increasingly limited due to selection for herbicide resistance, investigation of additional nonchemical tools becomes necessary. Harvest weed seed ...control (HWSC) is a methodology of weed management that targets and destroys weed seeds that are otherwise dispersed by harvesters following threshing. It is not known whether problem weeds in western Canada retain their seeds in sufficient quantities until harvest at a height suitable for collection. A study was conducted at three sites over 2 yr to determine whether retention and height criteria were met by wild oat, false cleavers, and volunteer canola. Wild oat consistently shed seeds early, but seed retention was variable, averaging 56% at the time of wheat swathing, with continued losses until direct harvest of wheat and fababean. The majority of retained seeds were >45 cm above ground level, suitable for collection. Cleavers seed retention was highly variable by site-year, but generally greater than wild oat. The majority of seed was retained >15 cm above ground level and would be considered collectable. Canola seed typically had >95% retention, with the majority of seed retained >15 cm above ground level. The suitability ranking of the species for management with HWSC was canola > cleavers > wild oat. Efficacy of HWSC systems in western Canada will depend on the target species and site- and year-specific environmental conditions. Nomenclature: False cleavers, Galium spurium L. GALSP; volunteer canola, Brassica napus L. BRSNN; wild oat, Avena fatua L. AVEFA; fababean, Vicia faba L.; wheat, Triticum aestivum L.
High costs of fertilizer in western Canada have generated interest in alternative N sources. Legumes produce N through fixation, and may increase soil residual and mineralizable N, thus reducing the ...need for fertilizer N in subsequent crops. Hybrid canola (Brassica napus L.) has a high N requirement for optimum yield, but knowledge of rotational effects of legumes on canola is limited. The objective was to determine the effects of legume and non‐legume preceding crops on yield and quality of canola grown the following year and malting barley (Hordeum vulgare L.) grown after canola. Field pea (Pisum sativum L.), lentil (Lens culinaris Medik.), faba bean (Vicia faba L.), canola, and wheat (Triticum aestivum L.) harvested for grain, and faba bean grown as a green manure were direct‐seeded at seven locations in 2009. Canola was seeded in 2010 and barley in 2011, with fertilizer N applied at 0, 30, 60, 90, and 120 kg ha−1. On average, all legumes, except faba bean for seed, produced higher canola and barley yields than when wheat was the preceding crop. Faba bean green manure produced the highest yields, while canola on canola produced the lowest canola yield. The legumes had little negative effect on canola oil or barley protein concentration. Yields of both crops increased with increasing N rate, but canola oil concentration decreased, and barley protein increased. The results indicate that growing legumes for seed before hybrid canola can improve canola and subsequent barley yield without negatively affecting canola oil or malting barley protein.
Over 90% of Canadian kochia populations are resistant to acetolactate synthase (ALS)– inhibiting herbicides. We questioned whether the target site–based resistance could affect plant growth and ...competitiveness. Homozygous F2 herbicide-resistant (HR) kochia plants with an amino acid substitution at Trp574 (sources: Alberta AB, Saskatchewan SK, and Manitoba MB), or Pro197 (MB, AB with two populations) were grown in replacement series with homozygous F2 herbicide-susceptible (HS) plants from the corresponding heterogeneous population (total: six populations). In pure stands, growth of HR plants from AB and SK was similar to that of HS plants, regardless of mutation; conversely, MB2-HR plants (Trp574Leu) developed more slowly and were taller than MB2-HS plants. Final dry weight of HR plants in pure stands was similar across all six populations, whereas that for HS plants in pure stands and HR–HS plants in mixed stands (50–50%) varied with population. Results for AB and SK populations suggest little impact of either ALS mutation on kochia growth, whereas those for MB lines would suggest an unidentified factor (or factors) affecting the HS, HR, or both biotypes. The variable response within and between lines, and across HS biotypes highlights the importance of including populations of various origins and multiple susceptible controls in HR biotype studies. Nomenclature: Kochia, Kochia scoparia (L.) Schrad. KCHSC.
Core Ideas
Soybean seed inoculation with Bradyrhizobium japonicum enhances grain production.
Greater inoculation response happens in Argentinean sites than in the United States.
Several soil ...properties and crop management practices are related with the responses to inoculation.
Although the relevance of biological N nutrition of soybean Glycine max (L.) Merr. is recognized worldwide, inoculation with Bradyrhizobium japonicum shows variable results and the benefit needs to be validated under current crop production practices. We conducted statistical analysis of soybean field trial data to provide insight into factors affecting the efficacy of soybean inoculation under contrasting crop production conditions. Most experimental sites, 187 trials in the United States and 152 trials in Argentina, were in soils with soybean history and naturalized B. japonicum strains. Yield increases were greater in Argentina (190 kg ha−1 equivalent to 6.39%) than in the United States (60 kg ha−1 equivalent to 1.67%). Tillage methods did not affect inoculant performance. In the United States, inoculation was more effective in soils with higher pH (>6.8) while in Argentina the greatest inoculation effect on crop production occurred in soils with a lower pH (<5.5). In the United States, where most of the trials were in rotation with corn (Zea mays L), the greatest positive effect of inoculation was observed in late planted soybean crops and independent of soil organic matter (SOM). In Argentina, the inoculant had its greatest effect in soils with no soybean history, a relatively high SOM, higher levels of soil extractable P and S, and in areas with greater precipitation during early reproductive growing stages. In both regions, the yield increases due to B. japonicum inoculation support the regular use of this practice to help provide adequate conditions for soybean production.
A conservation tillage study provided the opportunity to test whether tillage effects on the germinable weed seedbank would be consistent across different crop rotations and to investigate the ...potential residual effects of herbicide treatments terminated 12 yr earlier. Our objective was to measure the effects of tillage (moldboard plow MP vs. chisel plow CP vs. no-till NT), crop rotation (2-yr barley–red clover followed by 4-yr barley–canola–wheat–soybean rotation, compared to a cereal monoculture), and of a prior weed management factor (three intensity levels of herbicide use) on the density, diversity, and community structure of weed seedbanks. Species richness, evenness (Shannon's E), and diversity (Shannon's H′) of spring seedbanks varied little across treatments and over time. Total seedbank density generally increased as tillage was reduced, with some variations due to weed management in 1993 and crop rotation in 2006. Crop rotations generally had smaller seedbanks with fewer species than the monoculture. In 1993, seedbanks with minimum weed management were twice as dense as those with intensive or moderate weed management (approximately 6,000 vs. 3,000 seed m−2). By 2006, seed density averaged 6,838 seed m−2 across intensive and moderate weed management regardless of tillage, but was nearly twice as large in NT (12,188 seed m−2) compared to MP (4,770 seed m−2) and CP (7,117 seed m−2) with minimum weed management (LSD0.005 = 4488). Species with abundant seedbanks responded differently to treatments. Barnyardgrass and green foxtail had larger seedbanks in the monoculture than in the rotation. Common lambsquarters and pigweed species had large seedbanks in tilled treatments in the rotation, whereas yellow foxtail and field pennycress contributed to the large seedbanks observed in NT treatments. The latter two species were also associated with residual effects of weed management treatments (terminated 12 yr earlier) in NT. The differential seedbank response of weed species, attributed in part to contrasting weed emergence patterns and agronomic practice effects on seed rain, explained some of the weak treatment effects observed for total seedbank density and diversity. The large weed seedbanks observed in NT plots after 18 yr confirms the importance of seed rain and seedbank management for the sustainability of NT systems. Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv.; common lambsquarters, Chenopodium album L.; green foxtail, Setaria viridis (L.) Beauv.; field pennycress, Thlaspi arvense L.; pigweed species, Amaranthus sp.; yellow foxtail, Setaria pumila (Poir.) Roem & Schult.
Advances in cultivar development and the demand for winter wheat (Triticum aestivum L.) as an ethanol feedstock has increased winter wheat acreage across the Canadian Prairies. A sustainable ...production package is required to maintain this renewed interest. Experiments were established in 2002–2004 at Lethbridge and Lacombe, AB, to determine cultivar, seeding rate, and herbicide effects on weed competition and crop yield. Treatments included a factorial combination of four contrasting cultivars (Radiant, CDC Osprey, CDC Falcon, and CDC Ptarmigan), three seeding rates (300, 450, and 600 seeds m–2), and two herbicide treatments (fall only or fall plus a spring in-crop herbicide). CDC Ptarmigan yield was higher (12%) than the other cultivars. This was expected as CDC Ptarmigan has higher yield potential, but its ability to maintain high yields in the presence of weeds was unexpected. The yield of CDC Falcon and Radiant was similar, but CDC Falcon had inferior weed competitive ability, as shown by yield differences, relative to the other three cultivars. CDC Osprey yielded less than the other cultivars. Grain yield was reduced when planted at 600 seeds m–2 by 4%, but weed biomass was less (40%). Spring in-crop herbicide application reduced weed biomass, but the extra application did not improve grain yield. These results suggest winter wheat yields can be maintained without added inputs of spring herbicides, and greater stability of yield, winter survival, and competitiveness will usually occur with increased seeding rates.
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