• Authors:
    • Post, W. M.
    • West, T. O.
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 6
  • Year: 2002
  • Summary: Changes agricultural management can potentially increase the accumulation rate of soil organic C (SOC), thereby sequestering CO2 from the atmosphere. This study was conducted to quantify potential soil C sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur. Analyses of C sequestration rates were completed using a global database of 67 long-term agricultural experiments, consisting of 276 paired treatments. Results indicate, on average, that a change from conventional tillage (CT) to no-till (NT) can sequester 57 +/- 14 g C m(-2) yr(-1), excluding wheat (Triticum aestivum L.)-fallow systems which may not result in SOC accumulation with a change from CT to NT. Enhancing rotation complexity can sequester an average 20 +/- 12 g C m(-2) yr(-1), excluding a change from continuous corn (Zea mays L.) to corn-soybean (Glycine mar L.) which may not result in a significant accumulation of SOC. Carbon sequestration rates, with a change from CT to NT, can be expected to peak in 5 to 10 yr with SOC reaching a new equilibrium in 15 to 20 yr. Following initiation of an enhancement in rotation complexity, SOC may reach a new equilibrium in approximately 40 to 60 yr. Carbon sequestration rates, estimated for a number of individual crops and crop rotations in this study, can be used in spatial modeling analyses to more accurately predict regional, national, and global C sequestration potentials.
  • Authors:
    • Campbell, C. A.
    • Derksen, D. A.
    • Lafond, G. P.
    • Zentner, R. P.
  • Source: Soil & Tillage Research
  • Volume: 67
  • Issue: 1
  • Year: 2002
  • Authors:
    • van Kooten,G. C.
    • Shaikh,S. L.
    • Suchánek,P.
  • Source: Land Economics
  • Volume: 78
  • Issue: 4
  • Year: 2002
  • Summary: Land-use change and forestry projects are considered a low-cost option for addressing climate change mitigation. In Canada, afforestation is targeted to sequester enough carbon to meet one-fifth of its international obligations, and at lower cost than emissions reduction. We examine economic aspects of the institutions and incentives needed to encourage landowners in Canada to adopt tree planting on a large scale. Based on data from a survey of landowners, the transaction costs of getting landowners to convert their land from agriculture to plantation forests appear to be a significant obstacle, possibly increasing the costs of afforestation projects beyond what conventional economic analysis suggests.
  • Authors:
    • Entz, T.
    • Janzen, H. Henry
    • Ellert, B. H.
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 5
  • Year: 2002
  • Summary: Sensitive methods are essential to resolve small changes in soil C storage, such as those attained in sequestration projects, against much larger quantities of C already present. To measure temporal changes in C storage we proposed a high-resolution method based on collecting volumetric soil cores from a microsite (4 by 7 m), marking core locations to intersperse multiple cores collected initially and in a subsequent sampling year, rigorous analytical quality control, and calculating soil C pool sizes with proper corrections for unequal soil masses. To evaluate the method, we measured the recovery of 3.64 Mg C ha(-1) added as coal dust to microsites. We calculated C stored in successive soil layers of both fixed volume and equivalent mass. We inferred coal C recovery from spatial comparisons between coal-amended and unamended plots, and from temporal comparisons between soil samples collected before and after coal addition. The comparisons among C storage showed effective recovery of added coal C, but only for paired temporal differences based on calculations of organic C storage in an equivalent soil mass. With spatial comparisons, coal C became undetectable when soil thickness exceeded 35 cm. With temporal comparisons, coal C recovery ranged from 91 to 106%, provided differences were calculated for successively thicker layers of equivalent soil mass. In contrast, recovery was only 64 to 82% when temporal differences were calculated for layers of fixed soil volume. The method is useful to quantify small temporal changes in soil organic C storage within microsites, and possibly over more extensive areas with sufficient samples to characterize spatial variability.
  • Authors:
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 66
  • Issue: 2
  • Year: 2002
  • Summary: Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions. It is hypothesized that the degree of stratification of soil organic C and N pools with soil depth, expressed as a ratio, could indicate soil quality or soil ecosystem functioning, because surface organic matter is essential to erosion control, water infiltration, and conservation of nutrients. Stratification ratios allow a wide diversity of soils to be compared on the same assessment scale because of an internal normalization procedure that accounts for inherent soil differences. Stratification ratios of soil organic C were 1.1, 1.2 and 1.9 under conventional tillage (CT) and 3.4, 2.0 and 2.1 under no tillage (NT) in Georgia, Texas, and Alberta/British Columbia, respectively. The difference in stratification ratio between conventional and NT within an environment was inversely proportional to the standing stock of soil organic C to a depth of 15-20 cm across environments. Greater stratification of soil C and N pools with the adoption of conservation tillage under inherently low soil organic matter conditions (i.e., warmer climatic regime or coarse-textured soil) suggests that standing stock of soil organic matter alone is a poor indication of soil quality. Stratification of biologically active soil C and N pools (i.e., soil microbial biomass and potential activity) were equally or more sensitive to tillage, cropping intensity, and soil textural variables than stratification of total C and N. High stratification ratios of soil C and N pools could be good indicators of dynamic soil quality, independent of soil type and climatic regime, because ratios >2 would be uncommon under degraded conditions. Published by Elsevier Science B.V.
  • Authors:
    • Steiner, J. L.
    • Franzluebbers, A. J.
  • Source: Agricultural Practices and Policies for Carbon Sequestration in Soil
  • Year: 2002
  • Summary: No-tillage crop production has become an accepted practice throughout the U.S. The Kyoto Protocol on climate change has prompted great interest in conservation tillage as a management strategy to help sequester CO2 from the atmosphere into soil organic matter. Numerous reports published in recent years indicate a large variation in the amount of potential soil organic carbon (SOC) storage with no tillage (NT) compared with conventional tillage (CT). Environmental controls (i.e., macroclimatic variables of temperature and precipitation) may limit the potential of NT to store SOC. We synthesized available data on SOC storage with NT compared with CT from published reports representing 111 comparisons from 39 locations in 19 states and provinces across the U.S. and Canada. These sites provided a climatic continuum of mean annual temperature and precipitation, which was used to identify potential SOC storage limitations with NT. Soil organic C storage potential under NT was greatest (~0.050 kg · m -2· yr-1) in subhumid regions of North America with mean annual precipitation-to-potential evapotranspiration ratios of 1.1 to 1.4 mm · mm-1. Although NT is important for water conservation, aggregation, and protection of the soil surface from wind and water erosion in all climates, potential SOC storage with NT compared with CT was lowest in cold and dry climates, perhaps due to prevailing cropping systems that relied on low-intensity cropping, which limited C fixation. Published data indicate that increasing cropping intensity to utilize a greater fraction of available water in cold and dry climates can increase potential SOC storage with NT. These analyses indicate greatest potential SOC storage with NT would be most likely in the relatively mild climatic regions rather than extreme environments.
  • Authors:
    • Carter, M. R.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 1
  • Year: 2002
  • Summary: Soil quality concepts are commonly used to evaluate sustainable land management in agroecosystems. The objectives of this review were to trace the importance of soil organic matter (SOM) in Canadian sustainable land management studies and illustrate the role of SOM and aggregation in sustaining soil functions. Canadian studies on soil quality were initiated in the early 1980s and showed that loss of SOM and soil aggregate stability were standard features of nonsustainable land use. Subsequent studies have evaluated SOM quality using the following logical sequence: soil purpose and function, processes, properties and indicators, and methodology. Limiting steps in this soil quality framework are the questions of critical limits and standardization for soil properties. At present, critical limits for SOM are selected using a commonly accepted reference value or based on empirically derived relations between SOM and a specific soil process or function (e.g., soil fertility, productivity, or erodibility). Organic matter fractions (e.g., macro-organic matter, light fraction, microbial biomass, and mineralizable C) describe the quality of SOM. These fractions have biological significance for several soil functions and processes and are sensitive indicators of changes in total SOM. Total SOM influences soil compactibility, friability, and soil water-holding capacity while aggregated SOM has major implications for the functioning of soil in regulating air and water infiltration, conserving nutrients, and influencing soil permeability and erodibility. Overall, organic matter inputs, the dynamics of the sand-sized macro-organic matter, and the soil aggregation process are important factors in maintaining and regulating organic matter functioning in soil.
  • Authors:
    • Azooz, R.
    • Soon, Y.
    • Arshad, M.
  • Source: Soil & Tillage Research
  • Volume: 65
  • Issue: 1
  • Year: 2002
  • Summary: In recent years, crop rotation and no-till farming have become common practices in Alberta, Canada, and are widely recommended to maintain and/or enhance soil quality for sustained crop production, and improve environmental quality. This study was undertaken to evaluate the effects of rape ( Brassica rapa [ B. napus var. oleifera]) and field pea ( Pisum sativum) as replacements for summer fallow on wheat ( Triticum aestivum) production, and to determine the role of tillage (no-till versus modified no-till) on crop production on an Albright silt loam (Mollic Cryoboralf) near Beaverlodge, Alta. Spring wheat was grown for 2 years of the 3-year cropping cycle. Crop sequences studied were: rape-wheat-wheat (RWW), field pea-wheat-wheat (PWW) and fallow-wheat-wheat (FWW). The control was continuous wheat, i.e. wheat-wheat-wheat or monoculture wheat (MW). In modified no-till, sweeps attached to the seed drill pushed crop residues aside from the centre 7.5 cm of the seed row. Wheat yield following field pea increased by an average (1997-99) of 10.5% compared to monoculture wheat. Our data showed no measurable effect of rape on succeeding wheat yields compared to monoculture wheat. Wheat yields following fallow were intermediate between the RWW and PWW cropping systems. Residue management through the modified no-till system resulted in a warmer seedbed during spring and improved wheat production in all crop rotations studied, especially the first succeeding wheat. Modified no-till also resulted in higher yields of rape but not pea. Our data indicate that in a 3-year rotation with wheat, the preferred break crop would be field pea for the cold semiarid region of Alberta.
  • Authors:
    • Riveland, N.
    • Lafond, G.
    • Nielsen, D.
    • Brandt, S.
    • Miller, P.
    • Tanaka, D.
    • Johnston, A.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 2
  • Year: 2002
  • Summary: Oilseed crops are grown throughout the semiarid region of the northern Great Plains of North America for use as vegetable and industrial oils, spices and birdfeed. In a region dominated by winter and spring wheat ( Triticum aestivum), the acceptance and production of another crop requires that it both has an agronomic benefit to the cropping system and improve the farmers' economic position. In this review, we compare the adaptation and rotational effects of oilseed crops in the northern Great Plains. Rape ( Brassica sp. [ Brassica napus var. oleifera]), mustard ( B. juncea and Sinapis alba), and flax ( Linum usitatissimum) are well adapted to cool, short-season conditions found on the Canadian prairies and northern Great Plains border states of the USA. Sunflower ( Helianthus annuus) and safflower ( Carthamus tinctorius) are better adapted to the longer growing season and warmer temperatures found in the northern and central Great Plains states. Examples are presented of how agronomic practices have been used to manipulate a crop's fit into a local environment, as demonstrated with the early spring and dormant seeding management of rape, and of the role of no-till sowing systems in allowing the establishment of small-sown oilseed crops in semiarid regions. Continued evaluation of oilseed crops in rotation with cereals will further expand our understanding of how they can be used to strengthen the biological, economic and environmental role of the region's cropping systems. Specific research needs for each oilseed crop have been recommended.
  • Authors:
    • Lajeunesse, J.
    • Pageau, D.
    • Legere, A.
    • Simard, M.
    • Warwick, S.
  • Source: Weed Technology
  • Volume: 16
  • Issue: 2
  • Year: 2002
  • Summary: The presence of volunteer rape ( B. napus [ B. napus var. oleifera]) is becoming a significant agroecological concern, given the large-scale use of herbicide-tolerant varieties in some areas. Our goal was to estimate the frequency and persistence of volunteer rape in Quebec cropping systems by surveying fields that included a single rape crop since 1995 in Quebec, Canada. A survey was conducted in 131 fields in the main rape-growing areas of Quebec: in the Saguenay-Lac Saint-Jean region and the Quebec City-La Pocatiere area, Canada, during June-August 2000. Volunteer rape plants were counted in 0.25-m 2 quadrats every 10 m along a W pattern, and every 15 m along the margins of 88 fields. Volunteer rape plants were found in 90% of the fields surveyed and in a wide range of crops, including cereal, maize, and soyabean. Average densities of 4.9 and 3.9 plants/m 2 were found a year after rape production in fields and field margins, respectively. Volunteer rape densities decreased significantly over time. However, volunteer plants were still present at low densities 4 and 5 years after production. Dense stands of volunteer rape were found before postemergence herbicide application in no-till fields (9.84.1 plants/m 2), suggesting that, contrary to what was suggested in the literature, seeds could become dormant in no-till as well as in tilled systems. A small proportion of the volunteer rape plants observed in no-till fields near Quebec City and Ottawa included plants that had overwintered, either originating from autumn-germinated seedlings, harvested adult plants that had grown new leaves before the onset of winter, or spring regrowth from the base of unharvested adult plants from experimental plots. The presence and persistence of low densities of volunteer rape may not have been a cause of concern until now. However, producers should be made more aware of the potential short-term and long-term problems associated with potential gene flow between different herbicide-tolerant rape (HT rape) varieties and also between HT rape and related weed species.