• Authors:
    • Riznek, R.
    • Campbell, C.
    • Grant, B.
    • Smith, W.
    • Desjardins, R. L.
  • Source: Increasing Climate Variability and Change
  • Year: 2005
  • Summary: Carbon sequestration in agricultural soils is frequently promoted as a practical solution for slowing down the rate of increase of CO2 in the atmosphere. Consequently, there is a need to improve our understanding of how land management practices may affect the net removal of greenhouse gases (GHG) from the atmosphere. In this paper we examine the role of agriculture in influencing the GHG budget and briefly discuss the potential for carbon mitigation by agriculture. We also examine the opportunities that exist for increasing soil C sequestration using management practices such as reduced tillage, reduced frequency of summer fallowing, introduction of forage crops into crop rotations, conversion of cropland to grassland and nutrient addition via fertilization. In order to provide information on the impact of such management practices on the net GHG budget we ran simulations using CENTURY (a C model) and DNDC (a N model) for five locations across Canada, for a 30-yr time period. These simulations provide information on the potential trade-off between C sequestration and increased N2O emissions. Our model output suggests that conversion of cropland to grassland will result in the largest reduction in net GHG emissions, while nutrient additions via fertilizers will result in a small increase in GHG emissions. Simulations with the CENTURY model also indicated that favorable growing conditions during the last 15 yr could account for an increase of 6% in the soil C at a site in Lethbridge, Alberta.
  • Authors:
    • Follett, R. F.
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: The central USA contains some of the most productive agricultural land of the world. Due to the high proportion of land area committed to crops and pasture in this region, the carbon (C) stored and greenhouse gas (GHG) emission due to agriculture represent a large percentage of the total for the USA. Our objective was to summarize potential soil organic C (SOC) sequestration and GHG emission from this region and identify how tillage and cropping system interact to modify these processes. Conservation tillage (CST), including no-tillage (NT), has become more widespread in the region abating erosion and loss of organic rich topsoil and sequestering SOC.
  • Authors:
    • Government of Canada
  • Year: 2005
  • Summary: Canada's domestic Offset System is designed to encourage cost-effective domestic reductions or removals (i.e. carbon storage) of greenhouse gas emissions in activities that are not regulated. The System is a key element of the Government of Canada's plan to honour its commitments under the Kyoto Protocol.
  • Authors:
    • VandenBygaart, A. J.
    • Angers, D. A.
    • Rochette, P.
    • Gregorich, E. G.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: Agricultural soils can constitute either a net source or sink of the three principal greenhouse gases, carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). We compiled the most up-to-date information available on the contribution of agricultural soils to atmospheric levels of these gases and evaluated the mitigation potential of various management practices in eastern Canada and northeastern USA. Conversion of native ecosystems to arable cropping resulted in a loss of ~22% of the original soil organic carbon (C)--a release of about 123 Tg C to the atmosphere; drainage and cultivation of organic soils resulted in an additional release of about 15 Tg C. Management practices that enhance C storage in soil include fertilization and legume- and forage-based rotations. Adopting no-till did not always increase soil C. This apparent absence of no-till effects on C storage was attributed to the type and depth of tillage, soil climatic conditions, the quantity and quality of residue C inputs, and soil fauna. Emission of N2O from soil increased linearly with the amount of mineral nitrogen (N) fertilizer applied (0.0119 kg N2O-N kg N-1). Application of solid manure resulted in substantially lower N2O emission (0.99 kg N2O-N ha-1 year-1) than application of liquid manure (2.83 kg N2O-N ha-1 year-1) or mineral fertilizer (2.82 kg N2O-N ha-1 year-1). Systems containing legumes produced lower annual N2O emission than fertilized annual crops, suggesting that alfalfa (Medicago sativa L.) and other legume forage crops be considered different from other crops when deriving national inventories of greenhouse gases from agricultural systems. Plowing manure or crop stubble into the soil in the autumn led to higher levels of N2O production (2.41 kg N2O-N ha-1 year-1) than if residues were left on the soil surface (1.19 kg N2O-N ha-1 year-1). Elevated N2O emission during freeze/thaw periods in winter and spring, suggests that annual N2O emission based only on growing-season measurements would be underestimated. Although measurements of CH4 fluxes are scant, it appears that agricultural soils in eastern Canada are a weak sink of CH4, and that this sink may be diminished through manuring. Although the influence of agricultural management on soil C storage and emission of greenhouse gases is significant, management practices often appear to involve offsets or tradeoffs, e.g., a particular practice may increase soil C storage but also increase emission of N2O. In addition, because of high variability, adequate spatial and temporal sampling are needed for accurate estimates of greenhouse gas flux and soil C stock. Therefore a full accounting of greenhouse gas contributions of agricultural soils is imperative for determining the true mitigation potential of management practices.
  • Authors:
    • Rochette, P.
    • Pattey, E.
    • Lemke, R. L.
    • Wagner-Riddle, C.
    • Gregorich, E. G.
    • Ellert, B. H.
    • Drury, C. F.
    • Chantigny, M. H.
    • Janzen, H. H.
    • Helgason, B. L.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 72
  • Issue: 1
  • Year: 2005
  • Summary: Agricultural soils emit nitrous oxide (N2O), a potent greenhouse gas. Predicting and mitigating N2O emissions is not easy. To derive national coefficients for N2O emissions from soil, we collated over 400 treatment evaluations (measurements) of N2O fluxes from farming systems in various ecoregions across Canada. A simple linear coefficient for fertilizer-induced emission of N2O in non-manured soils (1.18% of N applied) was comparable to that used by the Intergovernmental Panel on Climate Change (IPCC) (1.25% of N applied). Emissions were correlated to soil and crop management practices (manure addition, N fertilizer addition and inclusion of legumes in the rotation) as well as to annual precipitation. The effect of tillage on emissions was inconsistent, varying among experiments and even within experiments from year to year. In humid regions (e.g., Eastern Canada) no-tillage tended to enhance N2O emissions; in arid regions (e.g., Western Prairies) no-tillage sometimes reduced emissions. The variability of N2O fluxes shows that we cannot yet always distinguish between potential mitigation practices with small (e.g., < 10%) differences in emission. Our analysis also emphasizes the need for developing consistent experimental approaches (e.g., 'control' treatments) and methodologies (i.e. measurement period lengths) for estimating N2O emissions.
  • Authors:
    • Zentner, R. P.
    • Liang, B. C.
    • Sherrod, L.
    • Gregorich, E. G.
    • Paustian, K.
    • Janzen, H. H.
    • Campbell, C. A.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 2
  • Year: 2005
  • Summary: Summer fallow (fallow) is still widely used on the North American Great Plains to replenish soil moisture between crops. Our objective was to examine how fallowing affects soil organic carbon (SOC) in various agronomic and climate settings by reviewing long-term studies in the midwestern USA (five sites) and the Canadian prairies (17 sites). In most soils, SOC increased with cropping frequency though not usually in a linear fashion. In the Canadian studies, SOC response to tillage and cropping frequency varied with climate--in semiarid conditions, SOC gains under no-till were about 250 kg ha-1 yr-1 greater than for tilled systems regardless of cropping frequency; in subhumid environments, the advantage was about 50 kg ha-1 yr-1 for rotations with fallow but 250 kg ha-1 yr-1 with continuous cropping. Specific crops also influenced SOC: Replacing wheat (Triticum aestivum L.) with lentil (Lens culinaris Medikus) had little effect; replacing wheat with lower-yielding flax (Linum usitatismum L.) reduced SOC gains; and replacing wheat with erosion-preventing fall rye (Secale cereale L.) increased SOC gains. In unfertilized systems, cropping frequency did not affect SOC gains, but in fertilized systems, SOC gains often increased with cropping frequency. In a Colorado study (three sites each with three slope positions), SOC gains increased with cropping frequency, but the response tended to be highest at the lowest potential evaporation site (where residue C inputs were greatest) and least in the toeslope positions (despite their high residue C inputs). The Century and the Campbell et al. SOC models satisfactorily simulated the relative responses of SOC although they underestimated gains by about one-third.
  • Authors:
    • Parton, W. J.
    • Del Grosso, S. J.
    • Paustian, K.
    • Conant, R. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 71
  • Issue: 3
  • Year: 2005
  • Summary: Carbon sequestration in agricultural, forest, and grassland soils has been promoted as a means by which substantial amounts of CO2 may be removed from the atmosphere, but few studies have evaluated the associated impacts on changes in soil N or net global warming potential (GWP). The purpose of this research was to (1) review the literature to examine how changes in grassland management that affect soil C also impact soil N, (2) assess the impact of different types of grassland management on changes in soil N and rates of change, and (3) evaluate changes in N2O fluxes from differently managed grassland ecosystems to assess net impacts on GWP. Soil C and N stocks either both increased or both decreased for most studies. Soil C and N sequestration were tightly linked, resulting in little change in C:N ratios with changes in management. Within grazing treatments N2O made a minor contribution to GWP (0.1-4%), but increases in N2O fluxes offset significant portions of C sequestration gains due to fertilization (10-125%) and conversion (average = 27%). Results from this work demonstrate that even when improved management practices result in considerable rates of C and N sequestration, changes in N2O fluxes can offset a substantial portion of gains by C sequestration. Even for cases in which C sequestration rates are not entirely offset by increases in N2O fluxes, small increases in N2O fluxes can substantially reduce C sequestration benefits. Conversely, reduction of N2O fluxes in grassland soils brought about by changes in management represents an opportunity to reduce the contribution of grasslands to net greenhouse gas forcing.
  • Authors:
    • Al-Kaisi, M. M.
    • Yin, X.
    • Licht, M. A.
  • Source: Applied Soil Ecology
  • Volume: 30
  • Issue: 3
  • Year: 2005
  • Summary: A wide range of tillage systems have been used by producers in the Corn-Belt in the United States during the past decade due to their economic and environmental benefits. However, changes in soil organic carbon (SOC) and nitrogen (SON) and crop responses to these tillage systems are not well documented in a corn-soybean rotation. Two experiments were conducted to evaluate the effects of different tillage systems on SOC and SON, residue C and N inputs, and corn and soybean yields across Iowa. The first experiment consisted of no-tillage (NT) and chisel plow (CP) treatments, established in 1994 in Clarion-Nicollet-Webster (CNW), Galva-Primghar-Sac (GPS), Kenyon-Floyd-Clyde (KFC), Marshall (M), and Otley-Mahaska-Taintor (OMT) soil associations. The second experiment consisted of NT, strip-tillage (ST), CP, deep rip (DR), and moldboard plow (MP) treatments, established in 1998 in the CNW soil association. Both corn and soybean yields of NT were statistically comparable to those of CP treatment for each soil association in a corn-soybean rotation during the 7 years of tillage practices. The NT, ST, CP, and DR treatments produced similar corn and soybean yields as MP treatment in a com-soybean rotation during the 3 years of tillage implementation of the second experiment. Significant increases in SOC of 17.3, 19.5, 6.1, and 19.3% with NT over CP treatment were observed at the top 15-cm soil depth in CNW, KFC, M, and OMT soil associations, respectively, except for the GPS soil association in a corn-soybean rotation at the end of 7 years. The NT and ST resulted in significant increases in SOC of 14.7 and 11.4%, respectively, compared with MP treatment after 3 years. Changes in SON due to tillage were similar to those observed with SOC in both experiments. The increases in SOC and SON in NT treatment were not attributed to the vertical stratification of organic C and N in the soil profile or annual C and N inputs from crop residue, but most likely due to the decrease in soil organic matter mineralization in wet and cold soil conditions. It was concluded that NT and ST are superior to CP and MP in increasing SOC and SON in the top 15 cm in the short-term. The adoption of NT or CP can be an effective strategy in increasing SOC and SON in the Corn-Belt soils without significant adverse impact on corn and soybean yields in a corn-soybean rotation.
  • Authors:
    • Dowbenko, R. E.
  • Source: Manitoba Agronomists Conference
  • Year: 2005
  • Authors:
    • Irvine, B.
    • Chen, Y.
    • Doan, V.
  • Source: Canadian Biosystems Engineering
  • Volume: 47
  • Year: 2005
  • Summary: A two-year field study was conducted to investigate the performance of seeding canola crop as influenced by types of residue (canola, wheat, and pea) and types of seed opener (disc and hoe). Seed placement (seeding depth and seed scattering index), speed of crop emergence, and plant populations were used to evaluate the seeding performance. Seeding placement as affected by field wheel tracks (inside and outside wheel tracks) was also examined. The results showed that the disc opener produced a greater seeding depth and faster emergence than the hoe opener. The two openers resulted in the same level of plant population. In the first year, plots with pea residue resulted in greater and more uniform seeding depth, faster emergence, and higher plant population than plots with wheat and canola residues. In the second year, a better uniformity of seeding depth was observed for pea residue than the other two types of residue, while there were no significant differences between residue types in the other measured variables due to the extremely dry soil condition in the spring of that year. Seeds were placed more uniformly outside the wheel track than inside the wheel track, while the mean seeding depths were similar inside and outside the wheel track.