- Authors:
- Jones, R.
- Hatfield, J. L.
- Chan, A. S. K.
- Parkin, T. B.
- Jarecki, M. K.
- Source: Journal of Environmental Quality
- Volume: 37
- Issue: 4
- Year: 2008
- Summary: The interactive effects of soil texture and type of N fertility (i.e., manure vs. commercial N fertilizer) on N2O and CH4 emissions have not been well established. This study was conducted to assess the impact of soil type and N fertility on greenhouse gas fluxes (N2O, CH4, and CO2) from the soil surface. The soils used were a sandy loam (789 g kg-1 sand and 138 g kg-1 clay) and a clay soil (216 g kg-1 sand, and 415 g kg-1 clay). Chamber experiments were conducted using plastic buckets as the experimental units. The treatments applied to each soil type were: (i) control (no added N), (ii) urea-ammonium nitrate (UAN), and (iii) liquid swine manure slurry. Greenhouse gas fluxes were measured over 8 weeks. Within the UAN and swine manure treatments both N2O and CH4 emissions were greater in the sandy loam than in the clay soil. In the sandy loam soil N2O emissions were significantly different among all N treatments, but in the clay soil only the manure treatment had significantly higher N2O emissions. It is thought that the major differences between the two soils controlling both N2O and CH4 emissions were cation exchange capacity (CEC) and percent water-filled pore space (%WFPS). We speculate that the higher CEC in the clay soil reduced N availability through increased adsorption of NH4+ compared to the sandy loam soil. In addition the higher average %WFPS in the sandy loam may have favored higher denitrification and CH4 production than in the clay soil.
- Authors:
- Source: Agronomy Journal
- Volume: 100
- Issue: 1
- Year: 2008
- Summary: Processing biomass through a distributed network of fast pyrolyzers may be a sustainable platform for producing energy from biomass. Fast pyrolyzers thermally transform biomass into bio-oil, syngas, and charcoal. The syngas could provide the energy needs of the pyrolyzer. Bio-oil is an energy raw material ([~]17 MJ kg-1) that can be burned to generate heat or shipped to a refinery for processing into transportation fuels. Charcoal could also be used to generate energy; however, application of the charcoal co-product to soils may be key to sustainability. Application of charcoal to soils is hypothesized to increase bioavailable water, build soil organic matter, enhance nutrient cycling, lower bulk density, act as a liming agent, and reduce leaching of pesticides and nutrients to surface and ground water. The half-life of C in soil charcoal is in excess of 1000 yr. Hence, soil-applied charcoal will make both a lasting contribution to soil quality and C in the charcoal will be removed from the atmosphere and sequestered for millennia. Assuming the United States can annually produce 1.1 x 109 Mg of biomass from harvestable forest and crop lands, national implementation of The Charcoal Vision would generate enough bio-oil to displace 1.91 billion barrels of fossil fuel oil per year or about 25% of the current U.S. annual oil consumption. The combined C credit for fossil fuel displacement and permanent sequestration, 363 Tg per year, is 10% of the average annual U.S. emissions of CO2-C.
- Authors:
- Hepperly, P.
- LaSalle, T. J.
- Year: 2008
- Authors:
- Plowden, Y.
- Benham, E. C.
- Franks, E. C.
- Salon, P. R.
- Dell, C. J.
- Source: Journal of Soil and Water Conservation
- Volume: 63
- Issue: 3
- Year: 2008
- Summary: No-till (NT) crop production is expected to sequester soil C, but little data is available for dairy forage systems. Our objective was to quantify impacts of NT and rye (Secale cereale L.) cover crops on soil C and N pools and associated soil properties on Pennsylvania dairies. Samples were collected from seven fields following corn harvest. The NT fields had approximately 50% more C and N in particulate and mineral-associated pools in the upper 5 cm (2 in) compared to conventional tillage, but C and N accumulations below 5 cm were similar. This suggests a C sequestration rate of ~0.5 Mg ha-1 y-1 (~0.2 tn ac-1 yr-1) in the 8 to 13 years NT has been used. Soil aggregate stability and cation exchange capacity were proportional to C pool sizes. Rye cover crops had no clear impact. Findings show that expected increases in C sequestration and soil quality with NT can be achieved in dairy forage systems.
- Authors:
- Source: Handout for US EPA Integrated Nitrogen Committee
- Year: 2008
- Authors:
- Wallander, R.
- Lemke, R. L.
- Miller, P. R.
- Engel, R. E.
- Dusenbury, M. P.
- Source: Journal of Environmental Quality
- Volume: 37
- Issue: 2
- Year: 2008
- Summary: Field measurements of N2O emissions from soils are limited for cropping systems in the semiarid northern Great Plains (NGP). The objectives were to develop N2O emission-time profiles for cropping systems in the semiarid NGP, define important periods of loss, determine the impact of best management practices on N2O losses, and estimate direct N fertilizer-induced emissions (FIE). No-till (NT) wheat (Triticum Aestivum L.)-fallow, wheat-wheat, and wheat-pea (Pisum sativum), and conventional till (CT) wheat-fallow, all with three N regimes (200 and 100 kg N ha-1 available N, unfertilized control); plus a perennial grass-alfalfa (Medicago sativa L.) system were sampled over 2 yr using vented chambers. Cumulative 2-yr N2O emissions were modest in contrast to reports from more humid regions. Greatest N2O flux activity occurred following urea-N fertilization (10-wk) and during freeze-thaw cycles. Together these periods comprised up to 84% of the 2-yr total. Nitrification was probably the dominant process responsible for N2O emissions during the post-N fertilization period, while denitrification was more important during freeze-thaw cycles. Cumulative -yr N2O-N losses from fertilized regimes were greater for wheat-wheat (1.31 kg N ha-1) than wheat-fallow (CT and NT) (0.48 kg N ha-1), and wheat-pea (0.71 kg N ha-1) due to an additional N fertilization event. Cumulative losses from unfertilized cropping systems were not different from perennial grass-alfalfa (0.28 kg N ha-1). Tillage did not affect N2O losses for the wheat-fallow systems. Mean FIE level was equivalent to 0.26% of applied N, and considerably below the Intergovernmental Panel on Climate Change mean default value (1.25%).
- Authors:
- Worth, D.
- Desjardins, R. L.
- Verge´, X. P. C.
- Dyer, J. A.
- Source: Canadian Journal of Soil Science
- Volume: 88
- Issue: 5
- Year: 2008
- Summary: Estimates of the efficiency of mitigation measures on reducing greenhouse gas (GHG) emissions from the agricultural sector are required. In this paper, recently calculated dairy GHG emissions for 2001 were extrapolated back to 1981 for census years using an index. The index was verified by comparing it with estimates based on the Intergovernmental Panel on Climate Change (IPCC) methodology for 1991. The index agreed with the IPCC estimates within 1% for methane and 4% for nitrous oxide on a national scale with no region having a difference of more than 5% for methane. For nitrous oxide, all regions were within 10%, except British Columbia, where the index was 19% too high. The index indicates that GHG emissions from primary milk production within the Canadian dairy industry have decreased by about 49% since 1981, mainly due to a 57% reduction in the dairy cow population during that period. The GHG emissions per kilogram of milk decreased by 35%, that is from 1.22 kg CO2eq kg-1 milk to 0.91 kg CO2eq kg-1 milk. Because this study took into account the energy-related CO2 emissions from all the major farm inputs (fertilizer and fossil fuel), there was little risk of hidden GHG emissions in the emission intensity calculation. This study demonstrates that where lack of input data restricts historical application of simulation models, a semi-empirical index approach can yield valuable results. Key words: Greenhouse gas, dairy industry, index, intensity indicator
- Authors:
- Source: Soil & Tillage Research
- Volume: 98
- Issue: 1
- Year: 2008
- Summary: As in other drained, intensively cultivated Histosols of the world, soil subsidence is a growing concern of vegetable farmers in the muck crops region of North Central, Ohio. Subsidence in organic soils is caused primarily by aerobic degradation of soil organic matter (SOM), which in turn makes available large quantities of once bound C and N. Upon drainage and cultivation, soil C and N dynamics shift drastically. Organic soils transition from CO2 and organic N sinks, to persistent sources, whereas CH4 uptake capacity increases. Therefore, this study was conducted to assess the short-term (within the first year) impact of conversion of intensively tilled organic soils to no-till management. The specific objectives of this study were to: (i) compare soil moisture content, soil temperature, and greenhouse gas (GHG) emission rates from moldboard/disking (MB), no-till (NT), and bare (B) treatments in cultivated organic soils, and (ii) estimate the rate of subsidence associated with these tillage practices. Over the year, soil moisture content (SMC) was significantly higher in MB (0.90 kg kg-1) than B (0.84 kg kg-1) treatments; however NT (0.87 kg kg-1) was not significantly different from either MB or B treatments. Mean annual temperatures at 5 cm depth were significantly higher in B (16.9 °C) compared to MB (16.2 °C) and NT (15.9 °C) treatments The CO2 emissions were not significantly different among treatments, while N2O emissions were significantly higher from MB (96.9 kg N2O-N ha-1 yr-1) than NT (35.8 kg N2O-N ha-1 yr-1) plots. Both CH4 uptake and CH4 emission exhibited low annual flux in all treatments.
- Authors:
- Alberta Environment and Water
- Year: 2008
