• Authors:
    • Zentner, R. P.
    • McGill, W. B.
    • Juma, N.
    • Ellert, B. H.
    • Izaurralde, R. C.
    • Campbell, C. A.
    • Janzen, H. H.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3
  • Year: 1998
  • Summary: The Canadian prairie, which accounts for about 80% of Canada's farmland, has large reserves of soil organic carbon (SOC). Changes in the size of the SOC pool have implications for soil productivity and for atmospheric concentrations of CO2, an important 'greenhouse gas'. We reviewed recent findings from long-term research sites to determine the impact of cropping practices on SOC reserves in the region. From this overview, we suggest that: (1) the loss of SOC upon conversion of soils to arable agriculture has abated; (2) significant gains in SOC (typically about 3 Mg C ha-1 or less within a decade) can be achieved in some soils by adoption of improved practices, like intensification of cropping systems, reduction in tillage intensity, improved crop nutrition, organic amendments, and reversion to perennial vegetation; (3) changes in SOC occur predominantly in 'young' or labile fractions; (4) the change in SOC, either gain or loss, is of finite duration and magnitude; (5) estimates of SOC change from individual studies are subject to limitations and are best viewed as part of a multi-site network; and (6) the energy inputs into agroecosystems need to be included in the calculation of the net C balance. The long-term sites indicate that Canadian prairie soils can be a net sink for CO2, though perhaps only in the short term. These sites need to be maintained to measure the effects of continued agronomic evolution and predicted global changes.
  • Authors:
    • Heinemeyer, O.
    • Lyon, D. J.
    • Drijber, R. A.
    • Doran, J. W.
    • Mosier, A. R.
    • Kessavalou, A.
  • Source: Journal of Environmental Quality
  • Volume: 27
  • Issue: 5
  • Year: 1998
  • Summary: Cropping and tillage management can increase atmospheric CO2, N2O, and CH4 concentrations, and contribute to global warming and destruction of the ozone layer. Fluxes of these gases in vented surface chambers, and water-filled pore space (WFPS) and temperature of survace soil were measured weekly from a long-term winter wheat (Triticum aestivum L.)-fallow rotation system under chemical (no-tillage) and mechanical tillage (noninversion subtillage at 7 to 10 cm or moldboard plowing to 15 cm) follow management and compared with those from "native" grass sod at Sidney, NE, from March 1993 to July 1995. Cropping, tillage, within-field location, time of year, soil temperature, and WFPS influenced net greenhouse gas fluxes. Mean annual interrow CO2 emissions from wheat-fallow ranged from 6.9 to 20.1 kg C ha-1 d-1 and generally increased with intensity and degree of tillage (no-till least and plow greatest). Nitrous oxide flux averaged summer > autumn > winter. Winter periods accounted for 4 to 10% and 3 to 47% of the annual CO2 and N2O flux, respectively, and 12 to 21% of the annual CH4 uptake. Fluxes of CO2 and N2O, and CH4 uptake increased linearly with soil temperature. No-till fallow exhibited the least threat to deterioration of atmospheric or soil quality as reflected by greater CH4 uptake, decreased N2O and CO2 emissions, and less loss of soil organic C than tilled soils. However, potential for increased C sequestration in this wheat-fallow system is limited due to reduced C input from intermittent cropping.
  • Authors:
    • Vitosh, M. L.
    • Pierce, F. J.
    • Christenson, D. R.
    • Peters, S. E.
    • Frye, W. W.
    • Blevins, R. L.
    • Dick, W. A.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3-4
  • Year: 1998
  • Summary: Soil organic matter has recently been implicated as an important sink for atmospheric carbon dioxide (CO2), However, the relative impacts of various agricultural management practices on soil organic matter dynamics and, therefore, C sequestration at spatial scales larger than a single plot or times longer than the typical three year experiment have rarely been reported. Results of maintaining agricultural management practices in the forest-derived soils of the eastern Corn (Zea mays L.) Belt states of Kentucky, Michigan, Ohio and Pennsylvania (USA) were studied. We found annual organic C input and tillage intensity were the most important factors in affecting C sequestration. The impact of rotation on C sequestration was primarily related to the way it altered annual total C inputs. The removal of above-ground plant biomass and use of cover crops were of lesser importance, The most rapid changes in soil organic matter content occurred during the first five years after a management practice was imposed with slower changes occurring thereafter. Certain management practices, e.g, no-tillage (NT), increased the soil's ability to sequester atmospheric CO2. The impact of this sequestration will be significant only when these practices are used extensively on a large percentage of cropland and when the C-building practices are maintained, Any soil C sequestered will be rapidly mineralized to CO2 if the soil organic matter building practices are not maintained,
  • Authors:
    • Paustian, K.
    • Elliott, E. T.
    • Doran, J. W.
  • Source: Soil & Tillage Research
  • Volume: 49
  • Issue: 1-2
  • Year: 1998
  • Summary: Two experiments were established in 1969 and 1970 near Sidney, NE, to determine the effect of moldboard plow (plow), sub-tillage (sub-till), and no-tillage (no-till) fallow management on soil properties, biological activities, and carbon and nitrogen cycling. One experiment was on land which had been broken from sod in 1920, seeded to crested wheatgrass [Agropyron cristatum (L.) Gaertn.] from 1957 to 1967, and cultivated for wheat again in 1967 (Previously Cultivated site). The second experiment was established on land that was in native mixed prairie sod until 1969 (Native Sod site), and compared the three tillage management practices listed above in a winter wheat-fallow system as well as replicated plots remaining in sod. Soil sampling done 10-12 years after these experiments were initiated, indicated that the biological environment near the soil surface (0-30 cm) with no-till was often cooler and wetter than that with conventional tillage management practices, especially moldboard plowing. Biological activity and organic C and N reserves were concentrated nearer the soil surface (0-7.6 cm) with no-tillage, resulting in greater potential for tie-up of plant available N in organic forms. However, regardless of tillage practice with wheat-fallow management at either site, long-term (22-27 years) losses of soil organic C from surface soil (0-30 cm) ranged from 12 to 32% (320-530 kg C ha(-1) year(-1)), respectively, for no-till and plowing. These soil C losses were closely approximated by losses measured to a depth of 122 cm, indicating that under the cropping, tillage, and climatic conditions of this study, soil C changes were adequately monitored by sampling to a depth of 30 cm within which most C loss occurs. No-till management maintains a protective surface cover of residue and partially decomposed materials near the soil surface. However, the decline in soil organic matter, and associated degradation in soil quality, will likely only be slowed by increasing C inputs to soil through use of a more intensive cropping system which increases the time of cropping and reduces the time in fallow. (C) 1998 Elsevier Science B.V. All rights reserved.
  • 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:
    • Zuberer, D. A.
    • Hons, F. M.
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3-4
  • Year: 1998
  • Summary: Quality of agricultural soils is largely a function of soil organic matter. Tillage and crop management impact soil organic matter dynamics by modification of the soil environment and quantity and quality of C input. We investigated changes in pools and fluxes of soil organic C (SOC) during the ninth and tenth year of cropping with various intensities under conventional disk-and-bed tillage (CT) and no tillage (NT). Soil organic C to a depth of 0.2 m increased with cropping intensity as a result of greater C input and was 10% to 30% greater under NT than under CT. Sequestration of crop-derived C input into SOC was 22+-2% under NT and 9+-4% under CT (mean of cropping intensities +- standard deviation of cropping systems). Greater sequestration of SOC under NT was due to a lower rate of in situ soil CO2 evolution than under CT (0.22+-0.03 vs.0.27+-0.06 g CO2-C g-1 SOC yr-1). Despite a similar labile pool of SOC under NT than under CT (1.1+-0.1 vs. 1.0+-0.1 g mineralizable C kg-1 SOC d-1), the ratio of in situ to potential CO2 evolution was less under NT (0.56+-0.03) than under CT (0.73+-0.08), suggesting strong environmental controls on SOC turnover, such as temperature, moisture, and residue placement. Both increased C sequestration and a greater labile SOC pool were achieved in this low-SOC soil using NT and high-intensity cropping.
  • 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:
    • Hütsch,B. W.
  • Source: Biology and Fertility of Soils
  • Volume: 27
  • Issue: 3
  • Year: 1998
  • Summary: The effect of land use and different soil tillage systems on CH4 oxidation was tested in a laboratory incubation study. Intact soil cores were collected from the topsoil (0–12 cm) of a field site with ploughed, direct-drilled and set-aside treatments, and from an adjacent undisturbed forest site. CH4 oxidation rates were 4.5 to 11 times higher in the direct-drilled than in the continuously ploughed treatment, in the set-aside soil they were intermediate. The oxidation rates in the forest soil were 11 times the highest rate measured at the field site, pointing to a distinct land use effect. Vertical profiles of CH4 oxidation activity revealed a very clear zonation in all treatments. CH4 oxidation increased significantly below the plough layer (0–25 cm), and showed a subsurface maximum under direct-drilling (5–15 cm) and under forest (5–10 cm). The vertical zonation under set-aside was comparable to that under ploughing. Generally, the maximum CH4 oxidizing activity was in the zone nearest to the soil surface, unless various constraints prevented this.
  • 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:
    • Doran, J. W.
    • Koerner, P. T.
    • Power, J. F.
    • Wilhelm, W. W.
  • Source: Soil Science Society of America Journal
  • Volume: 62
  • Issue: 5
  • Year: 1998
  • Summary: Returning crop residue improves water conservation and storage, nutrient availability, and crop yields, We have little knowledge, however, er, of the residual impacts of crop residues on soil properties and crop production. We hypothesized that residual impacts of crop residues vary with the amount of residues used. A 10-yr study near Lincoln, NE, evaluated the residual effects of an earlier 8-yr study of various crop residue amounts on crop growth and selected soil properties. From 1978 through 1985, crop residues were returned at 0, 50, 100, and 150% of the quantity produced by the previous crop (averaging 0 to approximate to 6 Mg ha(-1) yr(-1)). Continuous corn (Zea mays L.) was produced 1986 through 1995 on these plots, except sorghum [Sorghum bicolor (L.) Moench] was substituted in several years. To study management effects on residual responses, plots were subdivided with or without tillage, N fertilizer (60 kg N ha(-1)), and hairy vetch (Vicia villosa L.) cover crop. Residual effects of the 150% residue amount increased grain production 16% compared with the 0% amount (4900 vs. 4250 kg ha(-1), respectively), and were not affected by time or other management practices. Increasing previous residue amount did enhance soil N availability (from 73.0 to 82.3 kg autoclave-mineralizable N ha(-1)) and Bray soil P (16.7 to 20.3 kg ka(-1)). These results are among the first to show that residual effects of crop residue are prolonged (half-life of approximate to 10 yr) and probably result from changes in soil properties that enhance soil nutrient availability.