19722015
  • Authors:
    • Robertson, G. P.
    • Grace, P. R.
    • Bohm, S.
    • McSwiney, C. P.
  • Source: Journal of Natural Resources and Life Sciences Education
  • Volume: 39
  • Year: 2010
  • Summary: Opportunities for farmers to participate in greenhouse gas (GHG) credit markets require that growers, students, extension educators, offset aggregators, and other stakeholders understand the impact of agricultural practices on GHG emissions. The Farming Systems Greenhouse Gas Emissions Calculator, a web-based tool linked to the SOCRATES soil carbon process model, provides a simple introduction to the concepts and magnitudes of gas emissions associated with crop management. Users choose a county of interest on an introductory screen and are taken to the input/output window, where they choose crops, yields, tillage practices, or nitrogen fertilizer rates. Default values are provided based on convention and county averages. Outputs include major contributors of greenhouse gases in field crops: soil carbon change, nitrous oxide (N2O) emission, fuel use, and fertilizer. We contrast conventional tillage and no-till in a corn-soybean-wheat (Zea mays L.-Glycine max (L.) Merr.-Triticum aestivum L.) rotation and compare continuous corn fertilized at 101 and 134 kg N ha-1 yr-1. In corn years, N2O was the dominant GHG, due to high fertilizer requirements for corn. No-till management reduced greenhouse gas emissions by 50% due to net soil carbon storage. Continuous corn fertilized at 101 kg N ha-1 yr-1 emitted 1.25 Mg CO2 equivalents ha-1 yr-1 compared with 1.42 Mg CO2 equivalents ha-1 yr-1 at 134 kg N ha-1 yr-1, providing a 12% GHG savings. The calculator demonstrates how cropping systems and management choices affect greenhouse gas emissions in field crops.
  • Authors:
    • Hoben, J. P.
    • Gehl, R. J.
    • Grace, P. R.
    • Robertson, G. P.
    • Millar, N.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 15
  • Issue: 2
  • Year: 2010
  • Summary: Nitrous oxide (N2O) is a major greenhouse gas (GHG) product of intensive agriculture. Fertilizer nitrogen (N) rate is the best single predictor of N2O emissions in row-crop agriculture in the US Midwest. We use this relationship to propose a transparent, scientifically robust protocol that can be utilized by developers of agricultural offset projects for generating fungible GHG emission reduction credits for the emerging US carbon cap and trade market. By coupling predicted N2O flux with the recently developed maximum return to N (MRTN) approach for determining economically profitable N input rates for optimized crop yield, we provide the basis for incentivizing N2O reductions without affecting yields. The protocol, if widely adopted, could reduce N2O from fertilized row-crop agriculture by more than 50%. Although other management and environmental factors can influence N2O emissions, fertilizer N rate can be viewed as a single unambiguous proxy--a transparent, tangible, and readily manageable commodity. Our protocol addresses baseline establishment, additionality, permanence, variability, and leakage, and provides for producers and other stakeholders the economic and environmental incentives necessary for adoption of agricultural N2O reduction offset projects.
  • Authors:
    • Ellsworth, T. R.
    • Khan, S. A.
    • Mulvaney, R. L.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 2
  • Year: 2010
  • Summary: last paragraph: "In the modern era of intensified agriculture, soils are generally managed as a commodity to maximize short-term economic gain. Unfortunately, this concept entirely ignores the consequences for a vast array of biotic and abiotic soil processes that affect air and water quality and most important, the soil itself. After five decades of agrocentric management, the world's arable soils have been degraded and cereal production is increasingly exceeded by grain demand for a burgeoning human population. Should not an issue with global economic, political, and environmental ramifications be taken seriously?"
  • Authors:
    • Six, J.
    • Lee, J.
    • Temple, S. R.
    • Rolston, D. E.
    • Mitchell, J.
    • Kaffka, S. R.
    • Wolf, A.
    • De Gryze, S.
  • Source: Ecological Applications
  • Volume: 20
  • Issue: 7
  • Year: 2010
  • Summary: Despite the importance of agriculture in California's Central Valley, the potential of alternative management practices to reduce soil greenhouse gas (GHG) emissions has been poorly studied in California. This study aims at (1) calibrating and validating DAYCENT, an ecosystem model, for conventional and alternative cropping systems in California's Central Valley, (2) estimating CO2, N2O and CH4 soil fluxes from these systems, and (3) quantifying the uncertainty around model predictions induced by variability in the input data. The alternative practices considered were cover cropping, organic practices, and conservation tillage. These practices were compared with conventional agricultural management. The crops considered were beans, corn, cotton, safflower, sunflower, tomato, and wheat. Four field sites for which at least five years of measured data were available, were used to calibrate and validate the DAYCENT model. The model was able to predict 86% to 94% of the measured variation in crop yields and 69% to 87% of the measured variation in soil organic carbon (SOC) contents. A Monte-Carlo analysis showed that the predicted variability of SOC contents, crop yields and N2O fluxes was generally smaller than the measured variability of these parameters, in particular for N2O fluxes. Conservation tillage had the smallest potential to reduce GHG emissions among the alternative practices evaluated, with a significant reduction of the net soil GHG fluxes in two of the three sites of 336 ± 47 (mean ± standard error) and 550 ± 123 kg CO2-eq ha-1 yr-1. Cover cropping had a larger potential, with net soil GHG flux reductions of 752 ± 10, 1072 ± 272 and 2201 ± 82 kg CO2-eq ha-1 yr-1. Organic practices had the greatest potential for soil GHG flux reduction, with 4577 ± 272 kg CO2-eq ha-1 yr-1. Annual differences in weather or management conditions contributed more to the variance in annual GHG emissions than soil variability did. We concluded that the DAYCENT model was successful at predicting GHG emissions of different alternative management systems in California, but that a sound error analysis must accompany the predictions to understand the risks and potentials of GHG mitigation through adoption of alternative practices.
  • Authors:
    • Mauder, M.
    • MacPherson, J. I.
    • Srinivasan, R.
    • Grant, B.
    • Worth, D.
    • Smith, W. N.
    • Pattey, E.
    • Desjardins, R. L.
  • Source: Agricultural and Forest Meteorology
  • Volume: 150
  • Issue: 6
  • Year: 2010
  • Summary: Nitrous oxide (N2O) emissions are a large proportion of the agriculture sector's contribution to the greenhouse gas inventory of most developed countries. The spatial and temporal variability of N2O emissions from agricultural soils has long been considered the main factor limiting our ability to estimate N2O emissions, particularly the emissions associated with the spring snowmelt period. Tower and aircraft-based flux measurement systems and a process-based model were used to quantify N2O emissions for four years (2000, 2001, 2003 and 2004) in an agricultural area of eastern Canada, near Ottawa, where a corn-soybean crop rotation dominates. A tower-based system, which relies on the flux gradient technique, provided diurnal N2O emissions at a field scale. An aircraft-based system, which relies on the relaxed eddy accumulation technique, provided N2O emissions for two similar agricultural regions and the denitrification and decomposition (DNDC) model was used to estimate daily N2O emissions at a regional scale. In most cases, aircraft-based N2O emissions measurements were comparable for the two agricultural regions. Corresponding tower-based measurements which were collected over a field in the Ottawa area showed similar emission patterns to the aircraft-based measurements but in some cases the tower-based emissions were larger, as expected. This is because the footprint of aircraft-based measurements always incorporated a significant amount of crops such as soybean and other types of vegetation which do not receive additional nitrogen fertilization as well as waterlogged areas that do not emit N2O. While in three of the four years, the tower-based measurements were made over a tile drained field where nitrogen fertilizer had been applied the previous year. The N2O emissions patterns after planting were also similar for both aircraft and tower-based systems, but again they were slightly larger for the tower-based system. Aircraft-based N2O flux measurements are also compared to the N2O emissions obtained using the most recent version of the process-based model DNDC. Tests showed that DNDC gave comparable N2O emissions estimates for the measurement period as a whole, but was not always able to correctly predict the timing of peak emissions.
  • Authors:
    • ERS,USDA
  • Volume: 2012
  • Year: 2010
  • Authors:
    • Jackson, W.
    • Cox, T. S.
    • Cox, C. M.
    • Buckler, E. S.
    • Brummer, E. C.
    • Ibrahim, A. M. H.
    • Hulke, B. S.
    • Murray, S. C.
    • Jones, S. S.
    • Ploschuk, E.
    • Paterson, A. H.
    • Hu, F.
    • Culman, S. W.
    • Crews, T. E.
    • Xu, Y.
    • Wyse, D. L.
    • Wade, L. J.
    • Van Tassel, D. L.
    • Tao, D.
    • Snapp, S.
    • Sacks, E. J.
    • Borevitz, J.
    • Bell, L. W.
    • Reganold, J. P.
    • Glover, J. D.
    • Holland, J.
    • Gill, B. S.
    • Eriksson, D.
    • DeHaan, L. R.
  • Source: Science
  • Volume: 328
  • Issue: 5986
  • Year: 2010
  • Summary: Despite doubling of yields of major grain crops since the 1950s, more than one in seven people suffer from malnutrition. Global population is growing; demand for food, especially meat, is increasing; much land most suitable for annual crops is already in use; and production of nonfood goods (e.g., biofuels) increasingly competes with food production for land. The best lands have soils at low or moderate risk of degradation under annual grain production but make up only 12.6% of global land area (16.5 million km2). Supporting more than 50% of world population is another 43.7 million km2 of marginal lands (33.5% of global land area), at high risk of degradation under annual grain production but otherwise capable of producing crops. Global food security depends on annual grains—cereals, oilseeds, and legumes—planted on almost 70% of croplands, which combined supply a similar portion of human calories. Annual grain production, though, often compromises essential ecosystem services, pushing some beyond sustainable boundaries. To ensure food and ecosystem security, farmers need more options to produce grains under different, generally less favorable circumstances than those under which increases in food security were achieved this past century. Development of perennial versions of important grain crops could expand options.
  • Authors:
    • Alluvione, F.
    • Del Grosso, S. J.
    • Halvorson, A. D.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced-efficiency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. Nitrous oxide emissions were monitored from corn (Zea mays L.) based rotations receiving fertilizer rates of 246 kg N ha-1 when in corn, 56 kg N ha-1 when in dry bean (Phaseolus vulgaris L.), and 157 kg N ha-1 when in barley (Hordeum vulgare L. ssp. vulgare). Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn-dry bean (NT-CDb), and no-till corn-barley (NT-CB). In the NT-CC and CT-CC systems, a controlled-release, polymer-coated urea (ESN) and dry granular urea were compared. In the NT-CDb and NT-CB rotations, a stabilized urea source (SuperU) was compared with urea. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Cumulative growing season N2O emissions from urea and ESN application were not different under CT-CC, but ESN reduced N2O emissions 49% compared with urea under NT-CC. Compared with urea, SuperU reduced N2O emissions by 27% in dry bean and 54% in corn in the NT-CDb rotation and by 19% in barley and 51% in corn in the NT-CB rotation. This work shows that the use of no-till and enhanced-efficiency N fertilizers can potentially reduce N2O emissions from irrigated systems.
  • Authors:
    • Fine, P.
    • Clapp, C. E.
    • Zhang, Y.
    • Chen, D.
    • Venterea, R. T.
    • Bloom, P.
    • Tamir, G.
    • Bar-Tal, A.
    • Heller, H.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 2
  • Year: 2010
  • Summary: The use of organic residues as soil additives is increasing, but, depending on their composition and application methods, these organic amendments can stimulate the emissions of CO2 and N2O. The objective of this Study was to quantify the effects of management practices in irrigated sweet corn (Zea mays L.) on CO2 and N2O emissions and to relate emissions to environmental factors. In a 3-yr study, corn residues (CR) and pasteurized chicken manure (PCM) Were used as soil amendments compared with no residue (NR) under three management practices: shallow tillage (ST) and no tillage (NT) under consecutive corn crops and ST Without crop. Tillage significantly increased (P < 0.05) CO2 and N2O fluxes in residue-amended plots and in NR plots. Carbon dioxide and N2O fluxes were correlated with soil NH4 concentrations and with days since tillage and days since seeding, Fluxes of CO2 were correlated with soil water content, whereas N2O flux had higher correlation with air temperature. Annual CO2 emissions were higher with PCM than with CR and NR (9.7, 2.9, and 2.3 Mg C ha(-1), respectively). Fluxes of N2O were 34.4, 0.94, and 0.77 kg N ha(-1) yr(-1) with PCM, CR, and NR, respectively. Annual amounts of CO2-C and N2O-N emissions from the PCM treatments were 64 and 3% of the applied C and N, respectively. Regardless of cultivation practices, elevated N2O emissions were recorded in the PCM treatment. These emissions could negate some of the beneficial effects of PCM on soil properties.
  • Authors:
    • Robertson, G. P.
    • Grace, P. R.
    • Millar, N.
    • Gehl, R. J.
    • Hoben, J. P.
  • Source: Global Change Biology
  • Volume: 17
  • Year: 2010
  • Summary: Row-crop agriculture is a major source of nitrous oxide (N2O) globally, and results from recent field experiments suggest that significant decreases in N2O emissions may be possible by decreasing nitrogen (N) fertilizer inputs without affecting economic return from grain yield. We tested this hypothesis on five commercially farmed fields in Michigan, USA planted with corn in 2007 and 2008.