• Authors:
    • Pan, G.
    • Ogle, S.
    • Siebner, C.
    • McConkey, B.
    • Katterer, T.
    • Grace, P. R.
    • Goidts, E.
    • Etchevers, J.
    • Dodd, M.
    • Cerri, C. E. P.
    • Andren, O.
    • Paustian, K.
    • vanWesemael, B.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contribution of such networks to reducing the uncertainty of soil carbon balances. Some SMNs are designed to estimate country-specific land use or management effects on SOC stocks, while others collect soil carbon and ancillary data to provide a nationally consistent assessment of soil carbon condition across the major land-use/soil type combinations. The former use a single sampling campaign of paired sites, while for the latter both systematic (usually grid based) and stratified repeated sampling campaigns (5-10 years interval) are used with densities of one site per 10-1,040 km2. For paired sites, multiple samples at each site are taken in order to allow statistical analysis, while for the single sites, composite samples are taken. In both cases, fixed depth increments together with samples for bulk density and stone content are recommended. Samples should be archived to allow for re-measurement purposes using updated techniques. Information on land management, and where possible, land use history should be systematically recorded for each site. A case study of the agricultural frontier in Brazil is presented in which land use effect factors are calculated in order to quantify the CO2 fluxes from national land use/management conversion matrices. Process-based SOC models can be run for the individual points of the SMN, provided detailed land management records are available. These studies are still rare, as most SMNs have been implemented recently or are in progress. Examples from the USA and Belgium show that uncertainties in SOC change range from 1.6-6.5 Mg C ha-1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha-1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i. e. a spatially implicit upscaling approach).
  • Authors:
    • Beres, B. L.
    • Carcamo, H. A.
    • Dosdall, L. M.
    • Yang, R. C.
    • Evenden, M. L.
    • Spaner, D. M.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Most semiarid regions of the northern Great Plains are prone to wheat stem sawfly (Hymenoptera: Cephidae, Cephus cinctus Norton) attack. As an alternative to the wheat ( Triticum aestivum L.)-fallow system, our objective was to determine if continuous cropping infested wheat stubble would inhibit wheat stem sawfly (WSS) emergence. Adult sawfly emergence from undisturbed stubble was compared to stubble harrowed with heavy tine or rotary drum harrows before recropping. Adult emergence from a control of "no recropping" was compared to direct seeding infested stubble with (i) air drills configured with knife-type openers spaced 23 or 30 cm apart, (ii) an air drill configured with high disturbance shovel-type sweep openers, and (iii) a low disturbance air drill equipped with disc openers. Pre-seed heavy tine harrowing reduced adult sawfly emergence but usually required a high tension setting. No-till planting into infested spring wheat stubble also lowered WSS emergence compared to leaving the field fallow. A system of heavy tine harrows and an air drill equipped with knife openers spaced 30 cm apart reduced WSS adult emergence in spring by 50 to 70%. Grain yield was optimized in spring wheat with air drills equipped with narrow knife openers; in winter wheat optimal yield was obtained with the low disturbance disc drill configurations. Our results indicate incremental benefits from continuous cropping rather than fallowing fields infested with WSS, which is a sustainable alternative to conventional tillage. A systems approach is recommended that integrates these practices with diversified nonhost crop phases and resistant cultivars.
  • Authors:
    • Lupwayi, N.
    • Lemke, R.
    • Holzapfel, C.
    • May, W.
    • Lafond, G.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 2
  • Year: 2011
  • Summary: Including grain-legumes in cropping systems contributes to a reduction in greenhouse gas emissions and enhances agronomic and economic performance of cropping systems. The objective was to examine the potential for increasing the frequency of field pea ( Pisum sativum L.) (FP) in a spring wheat ( Triticum aestivum L.) (W)-based cropping system. Three crop rotations, continuous pea (C-Pea), W-FP, and W-W-FP, were evaluated over a 10-yr period (1998-2007) at Indian Head, SK. During the FPphase of C-Pea and W-FP, three starter N rates (5, 20, 40 kg N ha -1) were applied. One rate of N (80 kg N ha -1) was used in W. Rotation and N had similar effects on plant densities in either crop. Field pea grain yields were 25% lower with C-Pea than W-FP or W-W-FP but similar between W-FP and W-W-FP. Starter N had some effect on FP grain yields at the higher N rate in W-FP but not C-Pea. Spring wheat grain yields were 3% greater on FP than W stubble. Grain protein in FP was 3.1% higher on C-Pea than W-P or W-W-FP while grain protein in W was 1 g kg -1 higher on FP than W stubble. Crop water use efficiency in FP and W was not affected by crop rotation. Based on the results of this study, we conclude that the frequency of FP in cropping systems in the subhumid and semiarid areas can be increased intermittently with only a 1-yr cereal break between FP crops when combined with proper integrated crop management practices.
  • Authors:
    • Paliwal, J.
    • Mebatsion, H.
    • Jayas, D.
  • Source: Computers and Electronics in Agriculture
  • Volume: 80
  • Year: 2011
  • Summary: The variation in the shape of cereal grains, namely; barley, oat, rye and wheat (Canada Western Amber Durum and Canada Western Red Spring), were quantitatively evaluated using principal components analysis (PCA) based on elliptic Fourier descriptors. Grain image boundary contours were extracted from the digital images of kernels, expressed as chain-coded points and then approximated by 13 elliptic Fourier coefficients. After normalization of the size, rotation and starting point of the contours, four groups of coefficients namely; invariant, symmetrical, asymmetric and standardized Fourier coefficients were analyzed separately using PCA. The PCA based on the symmetric Fourier coefficients captured the shape variability of different grains with fewer principal components (PCs) than the rest. Results suggest that the major shape variations of grains can be summarized by the first two, five, eight and seventeen PCs of the symmetric, standardized, invariant and asymmetric Fourier coefficients, respectively, capturing about 99% of shape variations. The effect of growing regions on kernel shapes was also studied and results revealed that the shape variability is well captured by the PCA of the symmetric coefficients of the standardized Fourier descriptors.
  • Authors:
    • Olson, B.
    • Curtis, T.
    • Chanasyk, D.
    • Miller, J.
  • Source: Journal of Environmental Quality
  • Volume: 40
  • Issue: 3
  • Year: 2011
  • Summary: Application of beef cattle ( Bos taurus) manure based on nitrogen (N) requirements of crops has resulted in elevated concentrations of soil test phosphorus (P) in surface soils, and runoff from this cropland can contribute to eutrophication of surface waters. We conducted a 3-yr field study (2005-2007) on a Lethbridge loam soil cropped to dryland barley ( Hordeum vulgare) in southern Alberta, Canada to evaluate the effect of annual and triennial P-based and annual N-based feedlot manure on P and N in runoff. The manure was spring applied and incorporated. There was one unamended control plot. A portable rainfall simulator was used to generate runoff in the spring of each year after recent manure incorporation, and the runoff was analyzed for total P, total dissolved P, total particulate P, dissolved reactive P, total N, total dissolved N, total particulate N, NO 3-N, and NH 4-N. Annual or triennial P-based application resulted in significantly ( p≤0.05) lower (by 50 to 94%) concentrations or loads of mainly dissolved P fractions in runoff for some years compared with annual N-based application, and this was related to lower rates of annual manure P applied. For example, mean dissolved reactive P concentrations in 2006 and 2007 were significantly lower for the annual P-based (0.12-0.20 mg L -1) than for the annual N-based application (0.24-0.48 mg L -1), and mean values were significantly lower for the triennial P-based (0.06-0.13 mg L -1) than for the annual N-based application. In contrast, other P fractions in runoff were unaffected by annual P-based application. Our findings suggested no environmental benefit of annual P-based application over triennial P-based application with respect to P and N in runoff. Similar concentrations and loads of N fractions in runoff for the P- and N-based applications indicated that shifting to a P-based application would not significantly influence N in runoff.
  • Authors:
    • Gradin, B.
    • Holm, F.
    • Stevenson, F.
    • Leeson, J.
    • Legere, A.
    • Thomas, A.
  • Source: Weed Research
  • Volume: 51
  • Issue: 1
  • Year: 2011
  • Summary: Contrasting approaches to integrated weed management (IWM) for prairie cropping systems were evaluated by measuring weed response to six IWM systems in a wheat-oilseed rape-barley-pea rotation at Saskatoon and Watrous, Saskatchewan, Canada. The six IWM systems (high herbicide/zero tillage; medium herbicide/zero tillage; low herbicide/zero tillage; low herbicide/low tillage; medium herbicide/medium tillage; no herbicide/high tillage) included various combinations of seeding rate and date, herbicide timing and rate, and tillage operations, in order to achieve similar weed management levels. Changes in weed communities were assessed over 4 years by monitoring species composition and abundance at various times during the growth season. Principal response curves indicated a gradual increase in Thlaspi arvense, Chenopodium album, Amaranthus retroflexus and Fallopia convolvulus in the no herbicide/high tillage system. Winter and early spring annuals and perennials increased in most systems, but particularly in the low herbicide/zero tillage and medium herbicide/zero tillage systems. Although five of the six IWM systems provided similar results, changes in weed communities would suggest that operations could be revised to improve the overall management of certain weed species and reduce seed return in the no herbicide/high tillage system and in systems with low herbicide inputs and zero tillage. This study confirms the potential of contrasting IWM systems under the challenging environmental conditions of the Canadian Prairies.
  • Authors:
    • Bueckert, R.
    • Gan. Y.T.
    • Liu, L. P.
    • Rees, K. van
  • Source: Field Crops Research
  • Volume: 122
  • Issue: 3
  • Year: 2011
  • Summary: Oilseed and pulse crops have been increasingly used to diversify cereal-based cropping systems in semiarid environments, but little is known about the root characteristics of these broadleaf crops. This study was to characterize the temporal growth patterns of the roots of selected oilseed and pulse crops, and determine the response of root growth patterns to water availability in semiarid environments. Canola ( Brassica napus L.), flax ( Linum usitatissimum L.), mustard ( Brassica juncea L.), chickpea ( Cicer arietinum L.), field pea ( Pisum sativum L.), lentil ( Lens culinaris), and spring wheat ( Triticum aestivum L.) were tested under high- (rainfall+irrigation) and low- (rainfall only) water availability conditions in southwest Saskatchewan, in 2006 and 2007. Crops were hand-planted in lysimeters of 15 cm in diameter and 100 cm in length that were installed in the field prior to seeding. Roots were sampled at the crop stages of seedling, early-flower, late-flower, late-pod, and physiological maturity. On average, root length density, surface area, diameter, and the number of tips at the seedling stage were, respectively, 41, 25, 14, and 110% greater in the drier 2007 than the corresponding values in 2006. Root growth in all crops progressed rapidly from seedling, reached a maximum at late-flower or late-pod stages, and then declined to maturity; this pattern was consistent under both high- and low-water conditions. At the late-flower stage, root growth was most sensitive to water availability, and the magnitude of the response differed between crop species. Increased water availability increased canola root length density by 70%, root surface area by 67%, and root tips by 79% compared with canola grown under low-water conditions. Water availability had a marginal influence on the root growth of flax and mustard, and had no effect on pulse crops. Wheat and two Brassica oilseeds had greater root length density, surface area and root tips throughout the entire growth period than flax and three pulses, while pulse crops had thicker roots with larger diameters than the other species. Sampling roots at the late-flower stage will allow researchers to capture best information on root morphology in oilseed and pulse crops. The different root morphological characteristics of oilseeds, pulses, and wheat may serve as a science basis upon which diversified cropping systems are developed for semiarid environments.
  • Authors:
    • Bueckert, R.
    • Gan, Y. T.
    • Liu, L. P.
    • Rees, K. van
  • Source: Field Crops Research
  • Volume: 122
  • Issue: 3
  • Year: 2011
  • Summary: Root distribution patterns in the soil profile are the important determinant of the ability of a crop to acquire water and nutrients for growth. This study was to determine the root distribution patterns of selected oilseeds and pulses that are widely adapted in semiarid northern Great Plains. We hypothesized that root distribution patterns differed between oilseed, pulse, and cereal crops, and that the magnitude of the difference was influenced by water availability. A field experiment was conducted in 2006 and 2007 near Swift Current (50°15′N, 107°44′W), Saskatchewan, Canada. Three oilseeds [canola ( Brassica napus L.), flax ( Linum usitatissimum L.), mustard ( Brassica juncea L.)], three pulses [chickpea ( Cicer arietinum L.), field pea ( Pisum sativum L.), lentil ( Lens culinaris)], and spring wheat ( Triticum aestivum L.) were hand-planted in lysimeters of 15 cm in diameter and 100 cm in length which were pushed into soil with a hydraulic system. Crops were evaluated under low- (natural rainfall) and high- (rainfall+irrigation) water conditions. Vertical distribution of root systems was determined at the late-flowering stage. A large portion (>90%) of crop roots was mainly distributed in the 0-60 cm soil profile and the largest amount of crop rooting took place in the top 20 cm soil increment. Pulses had larger diameter roots across the entire soil profile than oilseeds and wheat. Canola had 28% greater root length and 110% more root tips in the top 10 cm soil and 101% larger root surface area in the 40 cm soil under high-water than under low-water conditions. In 2007, drier weather stimulated greater root growth for oilseeds in the 20-40 cm soil and for wheat in the 0-20 cm soil, but reduced root growth of pulses in the 0-50 cm soil profile. In semiarid environments, water availability did not affect the vertical distribution patterns of crop roots with a few exceptions. Pulses are excellent "digging" crops with a strong "tillage" function to the soil due to their larger diameter roots, whereas canola is more suitable to the environment with high availability of soil water that promotes canola root development.
  • Authors:
    • Middleton, A. B.
    • Bremer, E.
    • McKenzie, R. H.
    • Pfiffner, P. G.
    • Woods, S. A.
  • Source: Canadian Journal of Plant Science
  • Volume: 91
  • Issue: 2
  • Year: 2011
  • Summary: High crop productivity is essential for irrigated crops and may be strongly affected by decisions of seeding date and rate. An irrigated field experiment was conducted at two locations in southern Alberta for 4 yr to compare the impact of seeding date and rate on productivity and quality of nine cereal crops and two oilseed crops. Seeding rate was only evaluated on one date in late April or early May, when maximum yields were expected. Delayed seeding reduced crop yields by 0.6 to 1.7% per day after the end of April: flax ( Linum usitatissimum L.) ≤ CWRS wheat ( Triticum aestivum L.), feed triticale (* Triticosecale W.) ≤ CPS or SWS wheat ≤ triticale or barley ( Hordeum vulgare L.) silage ≤ durum ( T. turgidum L.), feed or malt barley
  • Authors:
    • Buckley, K. E.
    • Moulin, A. P.
    • Volkmar, K.
  • Source: Canadian Journal of Soil Science
  • Volume: 91
  • Issue: 4
  • Year: 2011
  • Summary: The potential for adverse effects on soil quality and erosion in pinto bean-potato rotations is significant due to low levels of residue input to the soil following potatoes or beans, and the effect of tillage on soil structure, particularly in sandy-textured soils typical of the potato-growing area of Manitoba. Soil quality is reduced by low inputs of residue and carbon commensurate with an increase in the proportion of small and unstable aggregates susceptible to erosion. Furthermore N and P concentrations at the soil surface may be affected by various management options including fall cover crops, application of straw and the use of composted manure. In a study conducted at Carberry, MB, from 2000 to 2006, KCI-extractible NO(3)-N and Olsen P were determined in the fall prior to seeding in each year of the study. Water-soluble P, determined in the fall of 2005 for selected treatments, increased with application of compost. Soil organic C, total N and the proportion of erodible (