• Authors:
    • Lal, R.
    • Puget, P.
  • Source: Soil & Tillage Research
  • Volume: 80
  • Issue: 1-2
  • Year: 2005
  • Summary: Minimum tillage practices are known for increasing soil organic carbon (SOC). However, not all environmental situations may manifest this potential change. The SOC and N stocks were assessed on a Mollisol in central Ohio in an 8-year-old tillage experiment as well as under two relatively undisturbed land uses; a secondary forest and a pasture, on the same soil type. Cropped systems had 51 +/- 4 (equiv. mass) Mg ha(-1) lower SOC and lower 3.5 +/- 0.3 (equiv. mass)Mg ha(-1) N in the top 30cm soil layer than Linder forest. Being a secondary forest, the loss in SOC and N stocks by cultivation may have been even more than these reported herein. No differences among systems were detected below this depth. The SOC stock in the pasture treatment was 29 +/- 3 Mg ha(-1), greater in the top 10 cm layer than in cultivated soils. but was similar to those tinder forest and no-till (NT). Among tillage practices (plow, chisel and NT) only the 0-5 cm soil layer under NT exhibited higher SOC and N concentrations. An analysis of the literature of NT effect on SOC stocks. using meta-analysis, suggested that NT would have an overall positive effect on SOC sequestration rate but with a greater variability of what was previously reported. The average sequestration rate of NT was 330 kg SOC ha(-1) year(-1) with a 95%, confidence interval ranging from 47 to 620 kg SOC ha(-1) year(-1). There was no effect of soil texture or crop rotation on the SOC sequestration rate that could year explain this variability. The conversion factor for SOC stock changes from plow to NT was equal to 1.04. This suggests that the complex mechanisms and pathways of SOC accrual warrant a cautious approach when generalizing the beneficial changes of NT on SOC stocks. (C) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Spokas, K. A.
    • Burger, M.
    • Venterea, R. T.
  • Source: Journal of Environmental Quality
  • Volume: 34
  • Issue: 5
  • Year: 2005
  • Summary: Comprehensive assessment of the total greenhouse gas (GHG) budget of reduced tillage agricultural systems must consider emissions of nitrous oxide (N2O) and methane (CH4), each of which have higher global warming potentials than carbon dioxide (CO2). Tillage intensity may also impact nitric oxide (NO) emissions, which can have various environmental and agronomic impacts. In 2003 and 2004, we used chambers to measure N2O, CH4, and NO fluxes from plots that had been managed under differing tillage intensity since 1991. The effect of tillage on non-CO2 GHG emissions varied, in both magnitude and direction, depending on fertilizer practices. Emissions of N2O following broadcast urea (BU) application were higher under no till (NT) and conservation tillage (CsT) compared to conventional tillage (CT). In contrast, following anhydrous ammonia (AA) injection, N2O emissions were higher under CT and CsT compared to NT. Emissions following surface urea ammonium nitrate (UAN) application did not vary with tillage. Total growing season non-CO2 GHG emissions were equivalent to CO2 emissions of 0.15 to 1.9 Mg CO2 ha-1 yr-1 or 0.04 to 0.53 Mg soil-C ha-1 yr-1. Emissions of N2O from AA-amended plots were two to four times greater than UAN- and BU-amended plots. Total NO + N2O losses in the UAN treatment were approximately 50% lower than AA and BU. This study demonstrates that N2O emissions can represent a substantial component of the total GHG budget of reduced tillage systems, and that interactions between fertilizer and tillage practices can be important in controlling non-CO2 GHG emissions.
  • Authors:
    • Lal, R.
    • Jacinthe, P. -A.
  • Source: Soil & Tillage Research
  • Volume: 80
  • Issue: 1-2
  • Year: 2005
  • Summary: Methane (CH4) oxidation potential of soils decreases with cultivation, but limited information is available regarding the restoration of that capacity with implementation of reduced tillage practices. A study was conducted to assess the impact of tillage intensity on CH4 oxidation and several C-cycling indices including total and active microbial biomass C (t-MBC, a-MBC), mineralizable C (Cmin) and N (Nmin), and aggregate-protected C. Intact cores and disturbed soil samples (0-5 and 5-15 cm) were collected from a corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation under moldboard-plow (MP), chisel-plow (CP) and no-till (NT) for 8 years. An adjacent pasture (60 years) soils were also sampled as references. At all sites, soil was a Kokomo silty clay loam (mesic Typic Argiaquolls). Significant tillage effects on t-MBC and protected C were found in the 0-5 cm depth. Protected C, a measure of C retained within macro-aggregates and defined as the difference in Cmin (CO2 evolved in a 56 days incubation) between intact and sieved (<2 mm) soil samples, amounted to 516, 162 and 121 mg C kg-1 soil in the 0-5 cm layer of the forest, pasture and NT soils, respectively. Protected C was negligible in the CP and MP soils. Methane uptake rate ([mu]g CH4-C kg-1 soil per day, under ambient CH4) was higher in forest (2.70) than in pasture (1.22) and cropland (0.61) soils. No significant tillage effect on CH4 oxidation rate was detected (MP: 0.82; CP: 0.41; NT: 0.61). These results underscore the slow recovery of the CH4 uptake capacity of soils and suggest that, to have an impact, tillage reduction may need to be implemented for several decades.
  • Authors:
    • Dell, C. J.
    • Venterea, R. T.
    • Sauer, T. J.
    • Allmaras, R. R.
    • Reicosky, D. C.
    • Johnson, J. M. F
  • 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. The rate of SOC storage in NT compared to conventional tillage (CT) has been significant, but variable, averaging 0.40 ± 0.61 Mg C ha-1 year-1 (44 treatment pairs). Conversion of previous cropland to grass with the conservation reserve program increased SOC sequestration by 0.56 ± 0.60 Mg C ha-1 year-1 (five treatment pairs). The relatively few data on GHG emission from cropland and managed grazing land in the central USA suggests a need for more research to better understand the interactions of tillage, cropping system and fertilization on SOC sequestration and GHG emission.
  • Authors:
    • Johnson, D. W.
    • Moeltner, K.
    • van Kooten, G. C.
    • Manley, J.
  • Source: Climatic Change
  • Volume: 68
  • Issue: 1-2
  • Year: 2005
  • Summary: Carbon terrestrial sinks are often seen as a low-cost alternative to fuel switching and reduced fossil fuel use for lowering atmospheric CO2. To determine whether this is true for agriculture, one meta-regression analysis (52 studies, 536 observations) examines the costs of switching from conventional tillage to no-till, while another (51 studies, 374 observations) compares carbon accumulation under the two practices. Costs per ton of carbon uptake are determined by combining the two results. The viability of agricultural carbon sinks is found to vary by region and crop, with no-till representing a low-cost option in some regions (costs of less than $10 per tC), but a high-cost option in others (costs of $100-$400 per tC). A particularly important finding is that no-till cultivation may store no carbon at all if measurements are taken at sufficient depth. In some circumstances no-till cultivation may yield a triple dividend of carbon storage, increased returns and reduced soil erosion, but in many others creating carbon offset credits in agricultural soils is not cost effective because reduced tillage practices store little or no carbon.
  • Authors:
    • Sherrod, L.
    • Robertson, G. P.
    • Peterson, G. A.
    • Halvorson, A. D.
    • Mosier, A. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 72
  • Issue: 1
  • Year: 2005
  • Summary: When appraising the impact of food and fiber production systems on the composition of the Earth's atmosphere and the 'greenhouse' effect, the entire suite of biogenic greenhouse gases - carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) - needs to be considered. Storage of atmospheric CO2 into stable organic carbon pools in the soil can sequester CO2 while common crop production practices can produce CO2, generate N2O, and decrease the soil sink for atmospheric CH4. The overall balance between the net exchange of these gases constitutes the net global warming potential (GWP) of a crop production system. Trace gas flux and soil organic carbon (SOC) storage data from long-term studies, a rainfed site in Michigan that contrasts conventional tillage (CT) and no-till (NT) cropping, a rainfed site in northeastern Colorado that compares cropping systems in NT, and an irrigated site in Colorado that compares tillage and crop rotations, are used to estimate net GWP from crop production systems. Nitrous oxide emissions comprised 40-44% of the GWP from both rain-fed sites and contributed 16-33% of GWP in the irrigated system. The energy used for irrigation was the dominant GWP source in the irrigated system. Whether a system is a sink or source of CO2, i.e. net GWP, was controlled by the rate of SOC storage in all sites. SOC accumulation in the surface 7.5 cm of both rainfed continuous cropping systems was approximately 1100 kg CO2 equivalents ha-1 y-1. Carbon accrual rates were about three times higher in the irrigated system. The rainfed systems had been in NT for >10 years while the irrigated system had been converted to NT 3 years before the start of this study. It remains to be seen if the C accrual rates decline with time in the irrigated system or if N2O emission rates decline or increase with time after conversion to NT.
  • Authors:
    • Andrasko, K.
    • DeAngelo, B.
    • Gillig, D.
    • McCarl, B.
    • Jones, K.
    • Depro, B.
    • Sommer, A. J.
    • Sohngen, B.
    • Murray, B. C.
  • Year: 2005
  • Summary: From executive summary: "This report evaluates the potential for additional carbon sequestration and GHG reductions in U.S. forestry and agriculture over the next several decades and beyond. It reports these reductions as changes from baseline trneds, starting in 2010 and projected out 100 years to 2110. The report employs the Forest and Agriculture Sector Optimization Model with Greenhouse Gases (FASOMGHG). FASOMGHG is a partial equilibrium economic model of the U.S. forest and agriculture sectors, with land use competition between them, and linkages to international trade. FASOMGHG includes most major GHG mitigation options in U.S. forestry and agriculture; accounts fo rchanges in CO2, GH4, and N2O from most activities; and tracks carbon sequestration and carbon losses over time. It also projects a dynamic baseline and reports all additional GHG mitigation as changes from that baseline. FASOMGHG tracks five forest product categories and over 2,000 production possibilities for field crops, livestock, and biofuels for private lands in the conterminous United States broken into 11 regions. Public lands are not included. FASOMGHG evaluates the joint economic and biophysical effects of a range of GHG mitigation scenarios, under which costs, mitigation levels, eligible activities, and GHG coverage may vary. The six scenarios evaluated in this report are constant GHG prices, rising GHG prices, fixed national mitigation levels, inclusion of selected mitigation activities only, incentive payments for CO2 only, and payments on a per-acre versus per-tonne basis. GHG mitigation incentives are estimated by dollars per tonne of CO2 equivalent ($/t CO2 Eq.) payments for four of the six scenarios above. The model and analysis cover the 100 years from 2010 to 2110, but three focus dates are highlighted: 2015, 2025, and 2055. FASOMGHG's standard GHG accounting and payment approach is a comprehensive, pay-as-you-go system, for all applicable GHGs and activities over time. The analysis reported here is unique from other studies conducted on forestry and agricultural mitigation options on a number of fronts. First, the range of covered activities across the sectors is wide. Most comparable studies look at just one of the sectors or at one or a small subset of activities within each secvtor, which this report examines a fairly comprehensive set of activites across the two sectos covering a vast majority of all GHG effects. Of particular note are the inclusions of biofuels and non-CO2 mitigation options in agriculture. Second, the intertemporal dynamics of the economic and biophysical systems within FASOMGHG allow for an accounting of mitigation over time and by region, and for quantification of leakage effects that other studies generally have not produced. And third, the inclusion of non-GHG co-effects allows insights into the multiple environmental and economic tradeoffs that pertain to GHG mitigation in these sectors.
  • Authors:
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: Agriculture in the southeastern USA can be highly productive (i.e., high photosynthetic fixation of atmospheric CO2) due to warm-moist climatic conditions. However, its impacts on greenhouse gas emissions and mitigation potential have not been thoroughly characterized. This paper is a review and synthesis of literature pertaining to soil organic C (SOC) sequestration and greenhouse gas emissions from agricultural activities in the southeastern USA. Conservation tillage is an effective strategy to regain some of the SOC lost following decades, and in some areas centuries, of intensive soil tillage and erosion. With conventional tillage (CT) as a baseline, SOC sequestration with no tillage (NT) was 0.42 ± 0.46 Mg ha-1 year-1 (10 ± 5 years). Combining cover cropping with NT enhanced SOC sequestration (0.53 ± 0.45 Mg ha-1 year-1) compared with NT and no cover cropping (0.28 ± 0.44 Mg ha-1 year-1). By increasing cropping system complexity, SOC could be increased by 0.22 Mg ha-1 year-1, irrespective of tillage management. Taking into account an average C cost of producing and transporting N fertilizer, SOC sequestration could be optimized at 0.24 Mg ha-1 year-1 with application of 107 kg N ha-1 year-1 on N-responsive crops, irrespective of tillage management. In longer-term studies (5-21 years), poultry litter application led to SOC sequestration of 0.72 ± 0.67 Mg ha-1 year-1 (17 ± 15% of C applied). Land that was previously cropped and converted to forages sequestered SOC at a rate of 1.03 ± 0.90 Mg ha-1 year-1 (15 ± 17 years). Limited data suggest animal grazing increases SOC sequestration on upland pastures. By expanding research on SOC sequestration into more diverse pasture and manure application systems and gathering much needed data on methane and nitrous oxide fluxes under almost any agricultural operation in the region, a more complete analysis of greenhouse gas emissions and potential mitigation from agricultural management systems would be possible. This information will be necessary for developing appropriate technological and political solutions to increase agricultural sustainability and combat environmental degradation in the southeastern USA.
  • 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:
    • Strickland, T. C.
    • Bednarz, C. W.
    • Truman, C. C.
    • Potter, T. L.
    • Bosch, D. D.
  • Source: Transactions of the ASAE
  • Volume: 48
  • Issue: 6
  • Year: 2005
  • Summary: Conservation tillage has significant potential as a water management tool for cotton production on sandy, drought-prone soils. Plant residue remaining at the soil surface from prior crops serves as a vapor barrier against water loss, reduces raindrop impact energy, slows surface runoff, and often increases infiltration. By increasing infiltration, the potential for greater plant-available water can be enhanced and irrigation requirements reduced. Five years of data were collected to quantify the hydrologic differences between strip till and conventional till production systems. Surface runoff and lateral subsurface flow were measured on six 0.2 ha plots in South Georgia in order to quantify the water-related effects of conservation tillage. Significant differences in surface and subsurface water losses were observed between the conventional and strip tilled plots. Surface runoff from the conventionally tilled plots exceeded that from the strip tilled plots, while subsurface losses were reversed. Surface runoff losses from the conventionally tilled plots exceeded those from the strip tilled plots by 81% (129 mm/year). Shallow lateral subsurface losses from the strip tilled plots exceeded those from the conventionally tilled plots by 73% (69 mm/year). Overall, a net annual gain of 60 mm of water was observed for the strip tilled plots.