• Authors:
    • Campbell, C. A.
    • Kirkwood, V.
    • Gregorich, E. G.
    • Monreal, C.
    • Tarnocai, C.
    • Desjardins, R. L.
    • Dumanski, J.
  • Source: Climatic Change
  • Volume: 40
  • Issue: 1
  • Year: 1998
  • Summary: Increasing carbon sequestration in agricultural soils in Canada is examined as a possible strategy in slowing or stopping the current increase in atmospheric CO2 concentrations. Estimates are provided on the amount of carbon that could be sequestered in soils in various regions in Canada by reducing summerfallow area, increased use of forage crops, improved erosion control, shifts from conventional to minimal and no-till, and more intensive use of fertilizers. The reduction of summerfallow by more intensive agriculture would increase the continuous cropland base by 8.1% in western Canada and 6.8% in all of Canada. Although increased organic carbon (OC) sequestration could be achieved in all agricultural regions, the greatest potential gains are in areas of Chernozemic soils. The best management options include reduction of summerfallow, conversion of fallow areas to hay or continuous cereals, fertilization to ensure nutrient balance, and adoption of soil conservation measures. The adoption of these options could sequester about 50-75% of the total agricultural emissions of CO2 in Canada for the next 30 years. However, increased sequestration of atmospheric carbon in the soil is possible for only a limited time. Increased efforts must be made to reduce emissions if long-term mitigation is to be achieved.
  • Authors:
    • Liang, B. C.
    • Anderson, D. W.
    • Greer, K. J.
    • Gregorich, E. G.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3
  • Year: 1998
  • Summary: Because of concerns about the eventual impact of atmospheric CO2 accumulations, there is growing interest in reducing net CO2 emissions from soil and increasing C storage in soil. This review presents a framework to assess soil erosion and deposition processes on the distribution and loss of C in soils. The physical processes of erosion and deposition affect soil C distribution in two main ways and should be considered when evaluating the impact of agriculture on C storage. First, these processes redistribute considerable amounts of soil C, within a toposequence or a field, or to a distant site. Accurate estimates of soil redistribution in the landscape or field are needed to quantify the relative magnitude of soil lost by erosion and accumulated by deposition. Secondly, erosion and deposition drastically alter the biological process of C mineralization in soil landscapes. Whereas erosion and deposition only redistribute soil and organic C, mineralization results in a net loss of C from the soil system to the atmosphere. Little is known about the magnitude of organic C losses by mineralization and those due to erosion, but the limited data available suggest that mineralization predominates in the first years after the initial cultivation of the soil, and that erosion becomes a major factor in later years. Soils in depositional sites usually contain a larger proportion of the total organic C in labile fractions of soil C because this material can be easily transported. If the accumulation of soil in depositional areas is extensive, the net result of the burial (and subsequent reduction in decomposition) of this active soil organic matter would be increased C storage. Soil erosion is the most widespread form of soil degradation. At regional or global levels its greatest impact on C storage may be in affecting soil productivity. Erosion usually results in decreased primary productivity, which in turn adversely affects C storage in soil because of the reduced quantity of organic C returned to the soil as plant residues. Thus the use of management practices that prevent or reduce soil erosion may be the best strategy to maintain, or possibly increase, the worlds soil C storage.
  • Authors:
    • Izaurralde, R.
    • Gill, K.
    • Arshad, M.
  • Source: Journal of Sustainable Agriculture
  • Volume: 12
  • Issue: 2/3
  • Year: 1998
  • Summary: Properties of a silt loam (Dark Gray Luvisol), weed population and wheat production ( Triticum aestivum) in canola ( Brassica campestris)-wheat-wheat (C), fallow-wheat-wheat (F), field pea ( Pisum sativum)-wheat-wheat (P) and continuous wheat (W) cropping systems were compared under conventional tillage (CT) and no-till (NT) in field trials near Beaverlodge, Alberta, Canada. Percentage of water stable aggregates (WSA) was reduced after a fallow season. Soil NO 3-N was similar among cropped plots which was significantly lower than fallow plots in two of the three years. Ammonium-N, extractable P and penetration resistance (PR) of soil were not affected by crop rotation. The W plots tended to have more weeds than both the first (W1) and second (W2) year wheat plots in rotations. Wheat appeared to suppress weeds better than canola, field pea or fallow. Average annual production of 3.95 t/ha as grain and 10.7 t/ha as above-ground dry matter (AGDM) by W1 were significantly greater than the corresponding production by W2 and W. Wheat grain and AGDM production in the two years of C, F, P and W systems were not significantly different in most cases. However, cumulative yields by C, P and W systems for three years of rotation were greater than the corresponding grain and AGDM yields from F rotation by 1.10-4.19 and 4.3-8.7 t/ha, respectively. Tillage did not affect NO 3-N, NH 4-N, P and WSA in soil but reduced its PR. The NT system provided better control of annual broadleaf weeds whereas perennial weeds were better controlled by CT. The CT system produced more grains (average of 0.42 t/ha per year) than NT system. Crop rotation by tillage interaction effects on soil properties, weed populations and crop yields were not significant which indicated that the crop rotations were equally effective under both the tillage systems. Benefits of crop rotation over monoculture in this study were of similar nature as in earlier studies conducted on fields already under annual cropping systems. Canola and field pea were more beneficial than wheat as previous-crop for wheat production. Replacing fallow with a crop resulted in increased crop production and straw returned to soil, reduced potential for leaching of NO 3-N, and improved water stable aggregation of soil.
  • Authors:
    • Potter, J. W.
    • Cerkauskas, R. F.
    • McKeown, A. W.
    • Van Driel, L.
  • Source: Canadian Journal of Plant Science
  • Volume: 78
  • Issue: 2
  • Year: 1998
  • Summary: A 6-yr (1987-1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Results of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with the highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT plots during the last 3 yr. No major trends in incidence and severity of bacterial and fungal diseases and of disorders of fruit were evident during the 5-yr period and neither fruit yield nor quality were significantly affected by these factors. Root-knot nematodes (Meloidogyne hapla Chitwood) were numerically less in the rye-tomato rotation than in other treatments; both root-knot and root lesion nematodes (Pratylenchus penetrans [Cobb]) tended to be less numerous under CT than under ST. Strip-tillage is feasible for machine harvest processing tomatoes. However, we are concerned about the tendency of tomatoes grown under reduced tillage to have lower yields than those grown under conventional tillage. More work is required on the interactions of cultivars, cover crops and nematodes in soil conservation systems.
  • Authors:
    • Naeth, M. A.
    • Chanasyk, D. S.
    • Sansom, J. J.
    • Bateman, J. C.
  • Source: Canadian Journal of Soil Science
  • Volume: 78
  • Issue: 4
  • Year: 1998
  • Summary: The effects of sulfur and gypsum amendments in conjunction with crop management (fallow/barley and forage) on soil physical properties, soil moisture and vegetation characteristics were measured on a sodic and calcareous sandy loam minespoil at the Highvale coal mine, west of Edmonton, Alberta. Amendment and crop management had no significant effect on bulk density, plant species composition, canopy cover, ground cover or annual aboveground biomass. Crop management significantly affected penetration resistance (which was generally higher under forage), while amendment treatments did not. Profile soil moisture was lowest within the gypsum-amended plots at all depths, and was similar for sulfur-amended and control plots. Crop management affected profile soil moisture, with significantly less moisture under continuous forage than fallow/barley. As percolation is critical to the effectiveness of amendments in the amelioration process, cereal/fallow rotations are more effective than continuous forage in facilitating that process.
  • Authors:
    • Lyon, D. J.
    • Peterson, G. A.
    • Halvorson, A. D.
    • Leavitt, S. W.
    • Follett, R. F.
    • Paul, E. A.
  • Source: Soil Science Society of America Journal
  • Volume: 61
  • Issue: 4
  • Year: 1997
  • Summary: The size and turnover rate of the resistant soil organic matter (SOM) fractions were measured by 14C dating and 13C/12C measurements. This involved soils archived in 1948, and recent samples, from a series of long-term sites in the North American Great Plains. A reevaluation of C dates obtained in the 1960s expanded the study scope. The 14C ages of surface soils were modern in some native sites and near modern in the low, moist areas of the landscape. They were much older at the catena summits. The 14C ages were not related to latitude although this strongly influenced the total SOM content. Cultivation resulted in lower C contents and increased the 14C age by an average of 900 yr. The 10- to 20-cm depths from both cultivated and native sites were 1200 yr older than the 0- to 10-cm depth. The 90- to 120-cm depth of a cultivated site at 7015 yr before present (BP) was 6000 yr older than the surface. The nonhydrolyzable C of this depth dated 9035 yr BP. The residue of 6 M HCl hydrolysis comprised 23 to 70% of the total soil C and was, on the average, 1500 yr older. The percentage of nonhydrolyzable C and its 14C age analytically identify the amount and turnover rate of the old resistant soil C.
  • Authors:
    • Cole, C. V.
    • Elliott, E. T.
    • Paustian, K.
    • Paul, E. A.
  • Year: 1997
  • Authors:
    • Parton, W. J.
    • Mueller, T.
    • Molina, J. A. E.
    • Li, C.
    • Komarov, A. S.
    • Klein-Gunnewiek, H.
    • Kelly, R. H.
    • Jensen, L. S.
    • Jenkinson, D. S.
    • Frolking, S.
    • Franko, U.
    • Coleman, K.
    • Chertov, O. G.
    • Arah, J. R. M.
    • McGill, W. B.
    • Powlson, D. S.
    • Smith, J. U.
    • Smith, P.
    • Thornley, J. H. M.
    • Whitmore, A. P.
  • Source: Geoderma
  • Volume: 81
  • Issue: 1-2
  • Year: 1997
  • Summary: Nine soil organic models were evaluated using twelve datasets from seven long-term experiments. Datasets represented three different land-uses (grassland, arable cropping and woodland) and a range of climatic conditions within the temperate region. Different treatments (inorganic fertilizer, organic manures and different rotations) at the same site allowed the effects of differing land management to be explored. Model simulations were evaluated against the measured data and the performance of the models was compared both qualitatively and quantitatively. Not all models were able to simulate all datasets; only four attempted all. No one model performed better than all others across all datasets. The performance of each model in simulating each dataset is discussed. A comparison of the overall performance of models across all datasets reveals that the model errors of one group of models (RothC, CANDY, DNDC, CENTURY, DAISY and NCSOIL) did not differ significantly from each other. Another group (SOMM, ITE and Verberne) did not differ significantly from each other but showed significantly larger model errors than did models in the first group. Possible reasons for differences in model performance are discussed in detail.
  • Authors:
    • Peterson, G. A.
    • Lyon, D. J.
    • Halvorson, A. D.
    • Leavitt, S. W.
    • Paul, E. A.
    • Follett, R. F.
  • Source: Soil Science Society of America Journal
  • Volume: 61
  • Issue: 4
  • Year: 1997
  • Summary: The purposes of this study were to improve knowledge of regional vegetation patterns of C-3 and C-4 plants in the North American Great Plains and to use delta(13)C methodology and long-term research sites to determine contributions of small-grain crops to total soil organic carbon (SOC) now present, Archived and recent soil samples were used, Detailed soil sampling was in 1993 at long-term sites near Akron, CO, and Sidney, NE, After soil sieving, drying, and deliming, SOC and delta(13)C were determined using an automated C/N analyzer interfaced to an isotope-ratio mass spectrometer, Yield records from long-term experimental sites were used to estimate the amount of C-3 plant residue C returned to the soil, Results from delta(13)C analyses of soils from near Waldheim, Saskatchewan, to Big Springs, TX, showed a strong north to south decrease in SOC derived from C-3 plants and a corresponding increase from C-4 plants. The delta(13)C analyses gave evidence that C-3 plant residue C (possibly from shrubs) is increasing at the Big Springs, TX, and Lawton, OK, sites, Also, delta(13)C analyses of subsoil and topsoil layers shows evidence of a regional shift to more C-3 species, possibly because of a cooler climate during the past few hundreds to thousands of years, Data from long-term research sites indicate that the efficiency of incorporation of small-grain crop residue C was about 5.4% during 84 Jr at Akron, CO, and about 10.5% : during 20 yr at Sidney, NE, The C-14 age of the SOC at 0- to IO-tm depth was 193 yr and at 30 to 45 cm was 4000 yr; C-14 age of nonhydrolyzable C was 2000 and 7000 yr for these same two respective depths, Natural partitioning of the C-13 isotope by the photosynthetic pathways of C-3 and C-4 plants provides a potentially powerful tool to study SOC dynamics at both regional and local scales.
  • Authors:
    • Martel, J.
    • Beyaert, R. P.
    • Donald, R. G.
    • Simard, R. R.
    • Voroney, R. P.
    • Liang, B. C.
    • Drury, C. F.
    • Gregorich, E. G.
    • Carter, M. R.
    • Bolinder, M. A.
    • Angers, D. A.
  • Source: Soil & Tillage Research
  • Volume: 41
  • Issue: 3-4
  • Year: 1997
  • Summary: Soil organic matter storage capacity in agroecosystems varies with soil type, climate and agricultural management practices. The effects of different tillage systems on organic C and N storage were determined for a range of soils of eastern Canada mainly under continuous corn and small grain cereal production. Soil profiles from eight sites on which comparative tillage experiments had been performed for up to 11 years were sampled to a 60 cm depth in four increments (0-10, 10-20, 20-40 and 40-60cm). Organic C and N contents and dry bulk density were determined for each sampling depth. Bulk density measurements showed that the total soil mass in the soil profiles was not influenced by the tillage systems. No significant differences were found between tillage treatments in the total organic C and N storage down to 60 cm depth; the soil profiles under no-till (NT) and chisel plowing (CP) generally did not contain more C and N than those under conventional moldboard plowing (MP). However, the depth distribution of soil C and N varied with tillage. In the surface 0-10cm, C and N contents were higher under NT than under MP, whereas at deeper levels (20-40cm) the reverse trend was observed. It is concluded than under eastern Canadian conditions, where crop production and residue inputs are not affected by tillage, reduced tillage systems would not result in the storage of more soil organic matter in the entire soil profile at least in a 5-10 year period. Placement of the residues would be a major factor influencing the C and N distribution at specific depths.