• Authors:
    • Carr, P. M.
    • Anderson, R. L.
    • Lawley, Y. E.
    • Miller, P. R.
    • Zwinger, S. F.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: Special Issue 01
  • Year: 2012
  • Summary: The use of killed cover crop mulch for weed suppression, soil erosion prevention and many other soil and crop benefits has been demonstrated in organic no-till or zero-till farming systems in eastern US regions and in Canada. Implements have been developed to make this system possible by terminating cover crops mechanically with little, if any, soil disturbance. Ongoing research in the US northern Great Plains is being conducted to identify cover crop species and termination methods for use in organic zero-till (OZ) systems that are adapted to the crop rotations and climate of this semi-arid region. Current termination strategies must be improved so that cover crop species are killed consistently and early enough in the growing season so that subsequent cash crops can be grown and harvested successfully. Delaying termination until advanced growth stages improves killing efficacy of cover crops and may provide weed-suppressive mulch for the remainder of the growing season, allowing no-till spring seeding of cash crops during the next growing season. Excessive water use by cover crops, inability of legume cover crops to supply adequate amounts of N for subsequent cash crops and failure of cover crops to suppress perennial weeds are additional obstacles that must be overcome before the use of killed cover crop mulch can be promoted as a weed control alternative to tillage in the US northern Great Plains. Use of vegetative mulch produced by killed cover crops will not be a panacea for the weed control challenges faced by organic growers, but rather one tool along with crop rotation, novel grazing strategies, the judicious use of high-residue cultivation equipment, such as the blade plow, and the use of approved herbicides with systemic activity in some instances, to provide organic farmers with new opportunities to incorporate OZ practices into their cropping systems. Emerging crop rotation designs for organic no-till systems may provide for more efficient use of nutrient and water resources, opportunities for livestock grazing before, during or after cash crop phases and improved integrated weed management strategies on organic farms.
  • Authors:
    • Fowler, D. B.
  • Source: Crop Science
  • Volume: 52
  • Issue: 1
  • Year: 2012
  • Summary: The traditional winter wheat ( Triticum aestivum L.) production area on the North American Great Plains extended as far north as southern Alberta, Canada. This paper reviews a research and development program initiated with the objective of expanding production north and east into higher winter stress areas of the Canadian prairies. Winter survival was considered the main limitation to production in this region. However, the widespread adoption of no-till seeding into standing stubble for snow trapping has proven to be a successful method of overwintering wheat if cold hardy cultivars are grown using recommended management practices. Plant breeding improvements have increased production potential and winter wheat has become western Canada's third largest wheat class. Average commercial yields of 149, 125, and 118% of spring wheat in Manitoba, Saskatchewan, and Alberta, respectively, have demonstrated the high yield potential that can be realized while employing environmentally sustainable crop management practices. In light of current environmental concerns, changing weather patterns, diminishing world wheat reserves, and an ever increasing global population to feed, one would assume that winter wheat production in western Canada would be widely embraced. However, marketing obstacles and difficulties inserting winter wheat into rotations, both of which have a direct influence on farmers' net returns, remain to be overcome for this potential to be fully realized.
  • Authors:
    • Harker, K. N.
    • O'Donovan, J. T.
    • Blackshaw, R. E.
    • Johnson, E. N.
    • Lafond, G. P.
    • May, W. E.
  • Source: Canadian Journal of Plant Science
  • Volume: 92
  • Issue: 4
  • Year: 2012
  • Summary: Canola seed costs are substantial, but only a relatively small proportion of planted seeds actually emerge as seedlings. Direct-seeded (no-till) experiments were conducted from 2008 to 2010 at four western Canada locations [Lacombe AB (2007-2010), Lethbridge AB, Indian Head SK, and Scott SK] to determine the influence of cultivar (hybrid vs. open-pollinated), seeding speed (6.4 vs. 11.2 k h -1), and seeding depth (1 vs. 4 cm) on the emergence, maturity, yield, and seed quality of glyphosate-resistant canola. Canola emergence density was positively associated with precipitation levels surrounding the time of seeding; other site and environmental predictors such as soil temperature, soil texture, soil organic matter, latitude and longitude did not consistently influence canola emergence density. The agronomic performance of hybrid canola, including seed yield and quality, was usually superior to open-pollinated canola, but there was no difference in emergence density between the two cultivars. However, the hybrid cultivar emerged 1 d earlier, grew faster and covered the ground more quickly than the open-pollinated cultivar; important results from a crop-weed competition standpoint. Although seeding depth did not influence average canola yield, it often had a major impact on canola emergence density. Under moist conditions, average canola emergence improved from 37 to 62% as seeding depth decreased from 4 to 1 cm, respectively. Seeding at a depth of 1 vs. 4 cm also decreased days to emergence, increased canola ground cover, decreased days to flowering and days to maturity and tended to decrease green seed levels. Relatively high canola emergence rates can reduce the need for additional herbicide applications, herbicide input costs and selection pressure for herbicide resistance. Relatively high canola stand densities can improve the ability of canola to successfully tolerate and accommodate biotic and abiotic stress.
  • Authors:
    • Vera, C. L.
    • Malhi, S. S.
    • Kutcher, H. R.
    • Willenborg, C. J.
    • Hall, L. M.
    • Dosdall, L. M.
    • Klein-Gebbinck, H.
    • Smith, E. G.
    • Lupwayi, N. Z.
    • Blackshaw, R. E.
    • O'Donovan, J. T.
    • Turkington, T. K.
    • Harker, K. N.
    • McLaren, D. L.
    • Grant, C. A.
    • May, W. E.
    • Lafond, G. P.
    • Gan, Y.
  • Source: Canadian Journal of Plant Science
  • Volume: 92
  • Issue: 2
  • Year: 2012
  • Summary: Relatively high prices and increasing demand for canola ( Brassica napus L.) have prompted growers to produce more canola on more cropland. Here we determine if canola seed yield and oil concentration can be increased over current levels with high levels of crop inputs. From 2008 to 2010, direct-seeded experiments involving two seeding rates (75 vs. 150 seeds m -2), two nitrogen rates (100 vs. 150% of soil test recommendation), and the presence or absence of polymer-coated nitrogen or fungicides, were conducted at eight western Canada locations in canola-wheat-canola or continuous canola rotations. Herbicides, insecticides and fertilizers other than nitrogen were applied as required for optimal canola production. Increasing recommended nitrogen rates by 50% increased canola yields by up to 0.25 Mg ha -1. High (150 seeds m -2) versus lower (75 seeds m -2) seeding rates increased canola yields by 0.07 to 0.16 Mg ha -1. Fungicide treatment or polymer-coated nitrogen blended with uncoated urea increased canola yields by 0.10 Mg ha -1 in 2010, but not in 2008. The highest canola input combination treatment following wheat (3.50 Mg ha -1) yielded substantially more than the same high input treatment following canola (3.22 Mg ha -1). Average site yields were influenced by site conditions such as soil organic matter, days to maturity, and temperature, but these site and environmental predictors did not alter treatment rankings. Using higher than the soil test recommended rate of nitrogen or planting 150 versus 75 seeds m -2 increased canola yields consistently across western Canada. Canola oil concentration varied among canola cultivars, but was consistently low when N rates were high (150% of recommended). Higher than normal seeding rates led to high canola seed oil concentration in some cases, but the effect was inconsistent.
  • Authors:
    • Paliwal, J.
    • Mebatsion, H.
    • Jayas, D.
  • Source: Biosystems Engineering
  • Volume: 111
  • Issue: 4
  • Year: 2012
  • Summary: An algorithm to classify cereal grains, namely: barley, oats, rye and wheat (Canada Western Amber Durum (CWAD) and Canada Western Red Spring (CWRS)) based on grain kernel shapes using invariant elliptic Fourier descriptors (IEFDs) was developed. Boundary contours were extracted from the digital images of kernels, expressed as chain-coded points and then approximated by 13 Fourier harmonics. After normalisation of the size, rotation and starting point of the contours, the IEFDs were determined. Based on the first three IEFDs, perfect classification was achieved for barley, CWAD, CWRS and rye. The classification accuracies of oats were 99.7% and 100% for the first three and five IEFDs, respectively.
  • Authors:
    • Li, Q.
    • Auld, H.
    • Cheng, C. S. Q.
    • Li, G. L.
  • Source: CLIMATIC CHANGE
  • Volume: 112
  • Issue: 3-4
  • Year: 2012
  • Summary: Synoptic weather typing and regression-based downscaling approaches have become popular in evaluating the impacts of climate change on a variety of environmental problems, particularly those involving extreme impacts. One of the reasons for the popularity of these approaches is their ability to categorize a complex set of meteorological variables into a coherent index, facilitating the projection of changes in frequency and intensity of future daily extreme weather events and/or their impacts. This paper illustrated the capability of the synoptic weather typing and regression methods to analyze climatic change impacts on a number of extreme weather events and environmental problems for south-central Canada, such as freezing rain, heavy rainfall, high-/low-streamflow events, air pollution, and human health. These statistical approaches are helpful in analyzing extreme events and projecting their impacts into the future through three major steps or analysis procedures: (1) historical simulation modeling to identify extreme weather events or their impacts, (2) statistical downscaling to provide station-scale future hourly/daily climate data, and (3) projecting changes in the frequency and intensity of future extreme weather events and their impacts under a changing climate. To realize these steps, it is first necessary to conceptualize the modeling of the meteorology, hydrology and impacts model variables of significance and to apply a number of linear/nonlinear regression techniques. Because the climate/weather validation process is critical, a formal model result verification process has been built into each of these three steps. With carefully chosen physically consistent and relevant variables, the results of the verification, based on historical observations of the outcome variables simulated by the models, show a very good agreement in all applications and extremes tested to date. Overall, the modeled results from climate change studies indicate that the frequency and intensity of future extreme weather events and their impacts are generally projected to significantly increase late this century over south-central Canada under a changing climate. The implications of these increases need be taken into consideration and integrated into policies and planning for adaptation strategies, including measures to incorporate climate change into engineering infrastructure design standards and disaster risk reduction measures. This paper briefly summarized these climate change research projects, focusing on the modeling methodologies and results, and attempted to use plain language to make the results more accessible and interesting to the broader informed audience. These research projects have been used to support decision-makers in south-central Canada when dealing with future extreme weather events under climate change.
  • Authors:
    • Bedard-Haughn, A.
    • Pare, M. C.
  • Source: GEODERMA
  • Volume: 189
  • Year: 2012
  • Summary: Arctic soils store great amounts of soil organic matter (SOM) that are likely to be affected by future climate changes. Knowledge of the ability of the soil to mineralize nitrogen (N) and release greenhouse gases (GHG) at the landscape scale is critical to predict and model future effects of climate change on Arctic SOM. The objective of this study was to investigate how soil gross N mineralization and GHG emissions vary across landscapes and Arctic ecosystems. This study was conducted in three Arctic ecosystems: Sub-Arctic (Churchill, MB), Low-Arctic (Daring Lake, NWT), and High-Arctic (Truelove Lowlands, NU). The topography was divided into five landform units: 1) upper (Up), 2) back (Back), and 3) lower (Low) slopes for catena sites and 4) hummock and 5) interhummock for hummocky sites (i.e., hummock in Churchill and ice-wedge polygons in Truelove). All sites were sampled near the end of their growing seasons (i.e., from two to three weeks before plant senescence). Soil gross N mineralization was measured in situ using a N-15 dilution technique, whereas soil GHG emissions (N2O, CH4, and CO2) were measured in situ using a multicomponent Fourier transform infrared gas analyzer combined with an automated dark chamber. For all ecosystems, topography significantly influenced soil gross N mineralization and CO2 emissions. Topography had no significant impact on N2O and CH4 fluxes most likely because net fluxes were extremely low throughout landscapes. Soil gross N mineralization and CO2 emissions increased from Up. Back, to Low and from hummock to interhummock landform units. For example, at Churchill, soil gross mineralization rates averaged 4 mg N-NH4+ kg(-1) in upper slopes and progressively increased to about 25 mg N-NH4+ kg(-1) d(-1) in the lower slopes. Similarly, CO2 emission rates at Daring Lake averaged 0.5 mu mol CO2 m(-2) s(-1) in upper slopes and progressively increased to about 2.3 mu mol CO2 m(-2) s(-1) in the lower slopes. Comparisons among ecosystems showed that Churchill (Sub-Arctic) had the highest gross N mineralization rates followed by Truelove (High-Arctic) and Daring Lake (Low-Arctic). Furthermore, Daring Lake had significantly higher CO2 emissions than Churchill and no difference in CH4 and N2O emissions between both ecosystems was found. These findings suggest that all factors influencing C and N cycling processes such as climate and human induced changes may not have similar effects across landscapes or across Arctic ecosystems.
  • Authors:
    • Zhang, X. B.
    • Gameda, S.
    • Qian, B. D.
    • De Jong, R.
  • Source: CLIMATIC CHANGE
  • Volume: 112
  • Issue: 2
  • Year: 2012
  • Summary: It is theoretically interesting for climate change detection and practically important for agricultural producers to know whether climate change has influenced agroclimatic conditions and, if so, what the potential impacts are. We present analyses on statistical differences in means and variances of agroclimatic indices between three 30-year periods in the 20th century (i.e., 1911-1940, 1941-1970 and 1971-2000). We found many occurrences of statistically significant changes in means between pairs of the three 30-year periods. The findings consistently support agroclimatic trends identified from trend analysis as an earlier growing season start and an earlier end to spring frost (SF), together with an extended growing season, more frost-free days (FFD) and more available heat units were often found in the later 30-year periods as compared to the earlier ones. In addition, this study provides more detailed quantitative information than the trend signals for the practical interests of agricultural applications. Significant changes were detected for SF and FFD at a much larger percentage of stations between the latter two 30-year periods (1941-1970 vs. 1971-2000) as compared to the earlier two periods (1911-1940 vs. 1941-1970). In contrast, changes in variances of the selected agroclimatic indices were less evident than changes in their means, based on the percentage of stations showing significant differences. We also present new climate averages of the selected agroclimatic indices that can be useful for agricultural planning and management.
  • Authors:
    • McLaughlin, N. B.
    • Reynolds, W. D.
    • Drury, C. F.
    • Yang, X. M.
    • Shi, X. H.
    • Zhang, X. P.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 120
  • Year: 2012
  • Summary: Ridge tillage (RT) creates a distinctly different soil environment relative to no-tillage (NT) and mouldboard plow tillage (MP), which may in turn affect soil properties. In this study, the impacts of long-term (29 years) RT on soil organic carbon (SOC), water content, bulk density and penetration resistance were compared with NT and MP tillage on a clay loam soil under a corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation. The ridges in RT were formed at 76-cm spacing and corn was planted in the center of the ridges whereas soybean was planted in the shoulders of the ridges at 38-cm spacing. Soil samples were collected from the ridge crest (i.e. corn row), from the two ridge shoulder positions and from the interrow (furrow) positions of the ridges to evaluate both the spatial and profile distributions of the selected soil properties under RT relative to NT and MP. Ridge tillage produced low SOC in the interrows, high SOC in the crests and medium SOC in the shoulders relative to MP and NT. Soil water content was higher in the interrows than in the crests of the ridges, while soil penetration resistance followed the reverse trend. No-tillage resulted in a distinct SOC stratification with significantly higher SOC in surface soil and slightly lower SOC in subsurface soil while a uniform distribution of SOC was observed in the plow layer of MP soil. Hence, RT produced different SOC, water content, bulk density and penetration resistance distributions than NT and MP. Twenty-nine years of RT management resulted in improved soil physical conditions in the plow layer for crop root growth relative to NT and greater SOC stocks within the plow layer compared to MP.
  • Authors:
    • Gan,T. Y.
    • Tanzeeba, S.
  • Source: CLIMATIC CHANGE
  • Volume: 112
  • Issue: 2
  • Year: 2012
  • Summary: The potential hydrologic impact of climatic change on three sub-basins of the South Saskatchewan River Basin (SSRB) within Alberta, namely, Oldman, Bow and Red Deer River basins was investigated using the Modified Interactions Soil-Biosphere-Atmosphere (MISBA) land surface scheme of Kerkhoven and Gan (Advances in Water Resources 29:808-826 2006). The European Centre for Mid-range Weather Forecasts global re-analysis (ERA-40) climate data, Digital Elevation Model of the National Water Research Institute, land cover data and a priori soil parameters from the Ecoclimap global data set were used to drive MISBA to simulate the runoff of SSRB. Four SRES scenarios (A21, A1FI, B21 and B11) of four General Circulation Models (CCSRNIES, CGCM2, ECHAM4 and HadCM3) of IPCC were used to adjust climate data of the 1961-1990 base period (climate normal) to study the effect of climate change on SSRB over three 30-year time periods (2010-2039, 2040-2069, 2070-2099). The model results of MISBA forced under various climate change projections of the four GCMs with respect to the 1961-1990 normal show that SSRB is expected to experience a decrease in future streamflow and snow water equivalent, and an earlier onset of spring runoff despite of projected increasing trends in precipitation over the 21st century. Apparently the projected increase in evaporation loss due to a warmer climate over the 21st century will offset the projected precipitation increase, leading to an overall decreasing trend in the basin runoff of SSRB. Finally, a Gamma probability distribution function was fitted to the mean annual maximum flow and mean annual mean flow data simulated for the Oldman, Bow and Red Deer River Basins by MISBA to statistically quantify the possible range of uncertainties associated with SRES climate scenarios projected by the four GCMs selected for this study.