• Authors:
    • Ogle, S. M.
    • Masanet, E.
    • Torn, M. S.
    • Mishra, U.
  • Source: GEODERMA
  • Volume: 189
  • Year: 2012
  • Summary: Regional assessments of change in soil organic carbon (SOC) stocks due to land-use change are essential for supporting policy and management decisions related to greenhouse gas emissions and mitigation through carbon sequestration in soils. We have developed an improved approach by integrating geostatistical techniques with the Intergovernmental Panel on Climate Change (IPCC) carbon inventory approach to assess the impact of no-till management and crop-residue retention on SOC changes at a regional scale. Specifically, the improved approach utilizes regression kriging (RK) to estimate reference carbon stocks for the IPCC method. In our case study, we compared the results from the RI( method with a simple averaging (SA) method to derive the reference stocks as implemented in the Tier 2 IPCC approach, for a seven state area of the Midwestern United States. Using this improved method, we predict that eliminating tillage and retaining crop residues on all croplands of the study area would result in 11,735 Gg C yr(-1) sequestration for 20 years in the top 30 cm of the soil profile. Most cropland area would sequester 02-0.75 Mg C ha(-1) yr(-1). However, at a few places, the predicted rate of sequestration was more than 0.75 Mg C ha(-1) yr(-1), with an upper limit of 1.1 Mg C ha(-1) yr(-1). The highest rates of carbon accumulation were associated with favorable environmental conditions, such as lower slope positions and cold, temperate, moist climates. Validating predicted SOC change at 18 sites with varying soil types and environmental conditions showed that the RK approach to estimate reference carbon stocks decreased global prediction errors by 45% relative to the default reference values. The increase in prediction accuracy was due to using spatially varying SOC stocks rather than simple data averaging to derive reference SOC values. The uncertainty analysis demonstrated that there was more precision in the results from the RK approach in comparison to the results from the SA approach. These results suggest that improved geostatistical approach is a promising technique for improving soil carbon inventories that utilize the IPCC method, and will provide more precise results for informing public policy and management decisions while retaining ease of application.
  • Authors:
    • Melo, W. J.
    • Nunes, L. A. P. L.
    • Leite, L. F. C.
    • Araujo, A. S. F.
    • Santos, V. B.
  • Source: GEODERMA Volume: 170 Pages:
  • Volume: 170
  • Year: 2012
  • Summary: The aim of this study was to investigate the response of soil microbial biomass and organic matter fractions during the transition from conventional to organic farming in a tropical soil. Soil samples were collected from three different plots planted with Malpighia glaba: conventional plot with 10 years (CON); transitional plot with 2 years under organic farming system (TRA); organic plot with 5 years under organic farming system (ORG). A plot under native vegetation (NV) was used as a reference. Soil microbial biomass C (MBC) and N (MBN), soil organic carbon (SOC) and total N (TN), soil organic matter fractioning and microbial indices were evaluated in soil samples collected at 0-5, 5-10, 10-20 and 20-40 cm depth. SOC and fulvic acids fraction contents were higher in the ORG system at 0-5 cm and 5-10 cm depths. Soil MBC was highest in the ORG, in all depths, than in others plots. Soil MBN was similar between ORG. TRA and NV in the surface layer. The lowest values for soil MBC and MBN were observed in CON plot. Soil microbial biomass increased gradually from conventional to organic farming, leading to consistent and distinct differences from the conventional control by the end of the second year.
  • Authors:
    • McLaughlin, N. B.
    • Reynolds, W. D.
    • Drury, C. F.
    • Yang, X. M.
    • Shi, X. H.
    • Zhang, X. P.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 120
  • Year: 2012
  • Summary: Ridge tillage (RT) creates a distinctly different soil environment relative to no-tillage (NT) and mouldboard plow tillage (MP), which may in turn affect soil properties. In this study, the impacts of long-term (29 years) RT on soil organic carbon (SOC), water content, bulk density and penetration resistance were compared with NT and MP tillage on a clay loam soil under a corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation. The ridges in RT were formed at 76-cm spacing and corn was planted in the center of the ridges whereas soybean was planted in the shoulders of the ridges at 38-cm spacing. Soil samples were collected from the ridge crest (i.e. corn row), from the two ridge shoulder positions and from the interrow (furrow) positions of the ridges to evaluate both the spatial and profile distributions of the selected soil properties under RT relative to NT and MP. Ridge tillage produced low SOC in the interrows, high SOC in the crests and medium SOC in the shoulders relative to MP and NT. Soil water content was higher in the interrows than in the crests of the ridges, while soil penetration resistance followed the reverse trend. No-tillage resulted in a distinct SOC stratification with significantly higher SOC in surface soil and slightly lower SOC in subsurface soil while a uniform distribution of SOC was observed in the plow layer of MP soil. Hence, RT produced different SOC, water content, bulk density and penetration resistance distributions than NT and MP. Twenty-nine years of RT management resulted in improved soil physical conditions in the plow layer for crop root growth relative to NT and greater SOC stocks within the plow layer compared to MP.
  • Authors:
    • Prasad, J. V. N. S.
    • Mishra, P. K.
    • Vittal, K. P. R.
    • Kundu, S.
    • Singh, A. K.
    • Lal, R.
    • Venkateswarlu, B.
    • Deshpande, A. N.
    • Srinivasarao, Ch
    • Mandal, U. K.
    • Sharma, K. L.
  • Source: GEODERMA
  • Volume: 175
  • Year: 2012
  • Summary: Soil fertility management and water conservation strongly impact soil quality and agronomic production of Vertisols. Thus the data from a 22-year of soil fertility management experiment conducted in semi arid tropical region of central India was used to evaluate the impact of input of crop residue carbon (C) through sorghum (Sorghum bicolor L) cultivation in post monsoon season in Vertisols. In addition, the use of chemical fertilizers and manuring on crop yield sustainability and soil organic carbon (SOC) sequestration was assessed to 1-m depth. Retention of crop residues of sorghum, and application of farmyard manure (FYM) equivalent to 25 kg N ha(-1) along with 25 kg N ha(-1) supplied through chemical fertilizers increased and maintained the SOC stock. Green leaf manuring with Leucaena clippings along with chemical fertilizers did not increase the SOC stock However, a conjunctive use of crop residues and Leucaena clippings increased the profile SOC stock (68.5 Mg ha(-1)), an overall SOC build up (39.8%) and a high amount of SOC sequestration (14.4 Mg C ha(-1)). These parameters were positively correlated with cumulative C input and also reflected in the sustainable yield index (SYI). Higher grain yield (1.19 Mg ha(-1)) through the application of 25 kg N (CR) + 25 kg N (Leucaena) was obtained. For every Mg increase in SOC stock in the root zone there was 0.09 Mg ha(-1) increase in grain yield of sorghum. Stabilization of the SOC stock (zero change under cropping) requires a minimum input of 1.1 Mg C ha(-1)year(-1). Application of 50 kg N ha(-1) through chemical fertilizer also maintained the SOC stock at the antecedent SOC level. Therefore, a combined use of organic manure (crop residues and FYM) or green leaf manure along with chemical fertilizer is essential to enhancing SOC sequestration in sorghum cultivation in Vertisols during the post monsoon season in central India.
  • Authors:
    • Dever, C.
    • Hancock, G. R.
    • Wells, T.
    • Murphy, D.
  • Source: GEODERMA
  • Volume: 170
  • Year: 2012
  • Summary: Soil organic carbon (SOC) has considerable spatial and temporal variability both at the hillslope and catchment scale as well as down the soil profile. In recent years the distribution of SOC down the soil profile has become an area of interest in the understanding of the carbon sequestration potential of soils. Most studies however have concentrated on highly disturbed agricultural sites with little data available for untitled locations. In this study the vertical distribution of SOC is examined at a grassland site in the Young River area of Western Australia that has remained undisturbed by human activity for 50 years. Soil physical properties (texture, rock content) as well as the distribution of the environmental tracers Cs-137 and Pb-210 were assessed with the aim of better understanding the transport processes which produce the observed vertical distribution of SOC. While no consistent relationship was found between SOC and soil physical properties significant relationships were found between the distribution of SOC and the environmental tracers, Cs-137 and Pb-210. Finite element simulations based on a diffusion/convection/decay model showed that the transport of Cs-137 and Pb-210 down the soil profile is likely to be driven by the same (primarily diffusive) processes. The same model used in conjunction with plant input and decay data generated from the RothC-26.3 soil carbon model revealed that transport of SOC down the soil profile, while also a diffusion process, was significantly slower indicating that different processes and/or pathways are involved in SOC transport at this site.
  • Authors:
    • Filley, T. R.
    • Yang, X.
    • Zhang, X.
    • Zhang, X.
    • Ding, X.
    • He, H.
    • Zhang, B.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 124
  • Year: 2012
  • Summary: Tillage practices affect soil microorganisms, which in turn influence many processes essential to the function and sustainability of soil. In this study, the changes in soil microbial biomass and community composition in response to conventional tillage (CT, moldboard plowing and post-harvest residue removal) and no-tillage (NT) practices were examined during a maize (Zea mays L.) growing season in a clay loam soil (Typic Hapludoll) in northeastern China. Soil samples were taken in May, June, July, August, and September of 2008 at 0-5, 5-10, and 10-20. cm depths. Microbial communities were characterized by phospholipid fatty acid (PLFA) analysis. While microbial biomass increased at the beginning then decreased toward the end of the growing season in CT soils, it showed the opposite trend in NT soils. Microbial community structure showed better distinction among sampling months than between tillage practices. These results suggest that seasonal variations in soil microbial communities could be greater than changes associated with tillage treatments. However, microbial biomass accumulation was tillage dependent. On average, NT treatment resulted in 21% higher microbial biomass in 0-5. cm depth than CT treatment (P<0.05). Higher fungi to bacteria ratio was also observed under NT than CT treatment at both the 0-5 and 5-10. cm sampling depths. These data demonstrate that examining the effect of management practices on soil quality based on soil microbial communities should consider seasonal changes in the environmental properties. It is strongly recommended that NT practice should be adopted as an effective component of an overall strategy to improve soil quality and sustainability in northeastern China.
  • Authors:
    • Liang, W.
    • Chen, L.
    • Wei, K.
    • Zhang, X.
    • Li, Q.
    • Zhang, S.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 124
  • Year: 2012
  • Summary: Tillage strongly affects the process of soil aggregate stabilization, which involves a variety of binding mechanisms interacting at a range of spatial scales. To understand how binding mechanisms interact to promote soil aggregation, the impacts of three tillage systems (no tillage (NT), ridge tillage (RT) and conventional tillage (CT)) on soil aggregate binding agents (i.e., organic carbon (SOC), microbial biomass and glomalin-related soil proteins (GRSPs)) and aggregation were studied in the black soil of Northeast China. Compared with CT, RT increased all the aggregate-associated SOC, and NT only increased the SOC in the microaggregates. However, the contents of microbial biomass and GRSPs within bulk soil and different aggregate fractions were higher in NT and RT than in CT. Among the four aggregate fractions, greater values of SOC, microbial biomass and easily extractable GRSP (EEGRSP) were found in microaggregates and macroaggregates, respectively; while the total GRSP (TGRSP) was distributed equally among aggregate fractions. Structural equation modelling revealed that SOC, microbial biomass, and GRSPs accounted for 79% of the variation in soil aggregation. Soil organic carbon influenced aggregate stability indirectly through the effects on MBC and MBN. Microbial biomass and glomalin were more important driving factors for aggregate stability in the RT and NT systems. Our results suggest that conservation tillage (RT and NT) is beneficial for soil structure due to its positive effects on aggregation processes in black soil region of Northeast China.
  • Authors:
    • Miller, R.
    • Rothstein, D.
    • Nikiema, P.
  • Source: Biomass & Bioenergy
  • Volume: 39
  • Year: 2012
  • Summary: We assessed the short-term effects of converting pastureland to hybrid poplar and willow bioenergy plantations on soil greenhouse gas (GHG) fluxes and nitrogen (N) leaching in northern Michigan, USA. We used static chambers to measure soil carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) efflux, and tension lysimeters to measure nitrate (NO3-) leaching, in newly-established poplar and willow plantation plots, and in reference pasture plots. Emissions of N2O increased markedly following cultivation with cumulative direct N2O emissions of 0.3, 4.6 and 5.9 Mg ha(-1) of CO2 equivalents (CO(2)eq) in the reference, willow and poplar plots, respectively. Similarly, land conversion resulted in large increases of NO3 leaching with losses of 2.6, 38.8 and 53.9 kg ha(-1) of N from the reference, willow and poplar plots, respectively. Soil CO2 fluxes were significantly affected by land-use conversion; soils from willow and poplar plots emitted 29-42% less CO2 relative to the reference plots. Greater root respiration in the pastureland likely explained the greater soil CO2 efflux in these plots. Estimates of the net GHG emissions due to land-use conversion were strongly influenced by assumptions regarding the root contribution (RC) to total soil CO2 efflux. Assuming an RC = 50%, we estimate that pastureland conversion at this site incurred GHG debts of 7.4 and 11.6 Mg ha(-1) y(-1) as CO(2)eq for willow and poplar, respectively, during the establishment year. These results demonstrate the need to include soil disturbance impacts on the N cycle in future life cycle assessment of these bioenergy crops. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Torbert, H.
    • Watts, D.
    • Way, T.
    • Mays, D.
    • Nyakatawa, E.
    • Smith, D.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 8
  • Year: 2012
  • Summary: Soil management practices can alter the natural balance at the soil-plant-atmosphere ecosystem interface, which can significantly affect the environment. This study compared CO2 fluxes in conventional tillage (CT) and no-tillage (NT) corn (Zea mays L.) production systems receiving poultry litter (PL) and ammonium nitrate (AN) fertilizers on a Decatur silt loam soil in the Tennessee Valley region of North Alabama from Spring 2008 to Fall 2009. Soil CO2 flux in CT plots (9.5 kg CO2 ha(-1) day(-1)) was significantly greater than that in NT plots (4.9 kg CO2 ha(-1) day(-1) in summer. Soil CO2 fluxes were lowest in fall where CT plots had a mean soil CO2 emission of 0.8 kg CO2 ha(-1) day(-1), while plots under NT and grass fallow system were sinks of CO2 with fluxes -0.6 and -1.0 kg CO2 ha(-1) day(-1), respectively. Mean soil CO2 flux averaged over seasons in NT plots was 36% lower than that in CT plots. Grass fallow plots were net sinks of CO2 with a mean CO2 flux of -0.4 kg CO2 ha(-1) day(-1). Our study showed that application of PL or AN fertilizer in NT systems can significantly reduce soil CO2 emissions compared to CT systems in corn production.
  • Authors:
    • Pergher, M.
    • Tomazi, M.
    • Pauletti, V.
    • de Moraes, A.
    • Zanatta, J. A.
    • Bayer, C.
    • Dieckow, J.
    • Piva, J. T.
  • Source: Plant and Soil
  • Volume: 361
  • Issue: 1-2
  • Year: 2012
  • Summary: Aims For tropical and subtropical soils, information is scarce regarding the global warming potential (GWP) of no-till (NT) agriculture systems. Soil organic carbon (OC) sequestration is promoted by NT agriculture, but this may be offset by increased nitrous oxide (N2O) emissions. We assessed the GWP of a NT as compared to conventional tillage (CT) in a subtropical Brazilian Ferralsol. Methods From September 2008 to September 2009 we used static chambers and chromatographic analyses to assess N2O and methane (CH4) soil fluxes in an area previously used for 3-4 years as a field-experiment. The winter cover crop was ryegrass (Lolium multiflorum Lam.) while in summer it was silage maize (Zea mays L.). Results The accumulated N2O emission for NT was about half that of CT (1.26 vs 2.42 kg N ha(-1) year(-1), P = 0.06). Emission peaks for N2O occurred for a month after CT, presumably induced by mineralization of residual nitrogen. In both systems, the highest N2O flux occurred after sidedressing maize with inorganic nitrogen, although the flux was lower in NT than CT (132 vs 367 mu g N m(-2) h(-1), P = 0.05), possibly because some of the sidedressed nitrogen was immobilized by ryegrass residues on the surface of the NT soil. Neither water-filled pore space (WFPS) nor inorganic nitrogen (NH (4) (+) and NO (3) (-) ) correlated with N2O fluxes, although at some specific periods relationships were observed with inorganic nitrogen. Soils subjected to CT or NT both acted as CH4 sinks during most of the experiment, although a CH4 peak in May (autumn) led to overall CH4 emissions of 1.15 kg CH4-C ha(-1) year(-1) for CT and 1.08 kg CH4-C ha(-1) year(-1) for NT (P = 0.90). The OC stock in the 0-20 cm soil layer was slightly higher for NT than for CT (67.20 vs 66.49 Mg ha(-1), P = 0.36). In the 0-100 cm layer, the OC stock was significantly higher for NT as compared to CT (234.61 vs 231.95 Mg ha(-1), P = 0.01), indicating that NT resulted in the sequestration of OC at a rate of 0.76 Mg ha(-1) year(-1). The CO2 equivalent cost of agronomic practices was similar for CT (1.72 Mg CO(2)eq ha(-1) year(-1)) and NT (1.62 Mg CO(2)eq ha(-1) year(-1)). However, NT reduced the GWP relative to CT (-0.55 vs 2.90 Mg CO(2)eq ha(-1) year(-1)), with the difference of -3.45 Mg CO(2)eq ha(-1) year(-1) (negative value implies mitigation) being driven mainly by OC sequestration. The greenhouse gas intensity (GHGI, equivalent to GWP/silage yield) was lower for NT than CT (-31.7 vs 171.1 kg CO(2)eq Mg-1 for silage maize). Conclusion As compared to CT, greenhouse gas emissions from a subtropical soil can be mitigated by NT by lowering N2O emissions and, principally, sequestration of CO2-C.