• Authors:
    • Benning, J. L.
    • Powers, W. J.
    • Kovar, J. L.
    • Russell, J. R.
    • Haan, M. M.
  • Source: Rangeland Ecology & Management
  • Volume: 60
  • Issue: 3
  • Year: 2007
  • Summary: The objectives of the current study were to determine the amounts of above- and below-ground plant biomass production, P uptake by forage, and P concentration of cool-season grass forage as influenced by management and season. Five forage management treatments were evaluated over 3 years in smooth bromegrass (Bromus inermis Leyss) pastures. Management practices were: ungrazed (U), hay harvest/fall stockpile grazing (HS), rotational stocking to residual sward heights of 10 (10R) or 5 (5R) cm, and continuous stocking to maintain sward height at 5 cm (5C). Forage samples were hand-clipped within and outside grazing exclosures monthly from April through November of each year and analyzed for mass and P concentration. Root samples were collected at the initiation and completion of the study for determination of root length density (RLD) and root surface area density (RSAD). Phosphorus concentrations of forage outside the grazing exclosures did not differ among 5C, 5R, and IOR treatments, which were greater than U paddocks in April and August and less than HS paddocks in June. Mean annual forage productivity was greater in HS, 10R, 5R, and 5C paddocks (6 744 +/- 62 kg center dot ha(-1) mean +/- SE) than in the U paddocks (1 872 +/- 255 kg center dot ha(-1)). Mean P concentration of forage outside exclosures was greatest during the spring (0.21 +/- 0.01%), and lowest during the fall (0.13 +/- 0.01%). Mean annual P uptake by forage followed the same trend as forage production, being greater in the HS, 10R, 5R, and 5C paddocks (13.9 +/- 2.0 kg center dot ha(-1)) than in the U paddocks (3.7 +/- 0.5 kg center dot ha(-1)). After 3 years, RLD decreased in the ungrazed paddocks, but was unchanged in the HS, 10R, 5R, and 5C paddocks. Forage production and P uptake by forage is stimulated by forage harvest, either by grazing or hay harvest in smooth bromegrass pastures.
  • Authors:
    • Hamerschlag, K.
  • Year: 2007
  • Authors:
    • Hao,X.
    • Kravchenko,A. N.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 1
  • Year: 2007
  • Summary: Management practice and soil texture are known to affect soil C. Relatively little information exists, however, on interactions between textural and management effects. The objective of this study was to evaluate management effects on soil total C along a textural gradient in well-drained Typic Hapludalfs in southwest Michigan. Three management practices considered in this study were conventional tillage (CT) and no-till (NT) both with conventional chemical inputs, and conventional tillage with leguminous cover crops and no chemical inputs (CT-cover). Four replicate plots were sampled for each practice, with approximately 100 soil samples taken at the 0- to 5-cm depth in each plot. In all management practices, the relationships of total C and N with clay + silt varied depending on the range of clay + silt values, with regression slopes at clay + silt 570 g kg-1. Total C in the CT-cover and NT treatments was higher than that in the CT treatment across the whole range of studied textures; however, a greater difference in total C between NT and CT occurred at greater clay + silt contents. Total C in the CT-cover and NT treatments were not different when clay + silt was 600 g kg-1. The results indicate that the potential for C accumulation in surface soils via NT treatment depends on soil texture.
  • Authors:
    • Wright, J.
    • Herrick, J.
    • Fredrickson, E.
    • Bestelmeyer, B.
    • Brown, J.
    • Skaggs, R.
    • Peters, D. P. C.
    • Havstad, K. M.
  • Source: Ecological Economics
  • Volume: 64
  • Issue: 2
  • Year: 2007
  • Summary: The over 300 million ha of public and private rangelands in the United States are characterized by low and variable precipitation, nutrient-poor soils, and high spatial and temporal variability in plant production. This land type has provided a variety of goods and services, with the provisioning of food and fiber dominating through much of the 20th century. More recently, food production from a rangeland-based livestock industry is often pressured for a variety of reasons, including poor economic returns, increased regulations, an aging rural population, and increasingly diverse interests of land owners. A shift to other provisioning, regulating, cultural, and supporting services is occurring with important implications for carbon sequestration, biodiversity, and conservation incentives. There are numerous goods and services possible from rangelands that can supply societal demands such as clean water and a safe food supply. The use of ecologically-based principles of land management remains at the core of the ability of private land owners and public land managers to provide these existing and emerging services. We suggest that expectations need to be based on a thorough understanding of the diverse potentials of these lands and their inherent limits. A critical provisioning service to rangelands will be management practices that either maintain ecological functions or that restore functions to systems that have been substantially degraded over past decades. With proper incentives and economic benefits, rangelands, in the U.S. or globally, can be expected to provide these historical and more unique goods and services in a sustainable fashion, albeit in different proportions than in the past.
  • Authors:
    • Qi, J.
    • Thelen, K.
    • Kravchenko, A.
    • Senthilkumar, S.
    • Huang, X.
  • Source: Geoderma
  • Volume: 141
  • Issue: 1-2
  • Year: 2007
  • Summary: Accurate mapping of total soil carbon is important for reliable assessment of carbon sequestration potential from a field to regional scales. Highly variable soil and topographical attributes of glacial till terrain cause difficulties in mapping soil carbon based only on a limited number of soil samples. The objectives of this study were to demonstrate the feasibility of mapping total soil carbon using newly developed on-the-go near-infrared spectroscopy (NIRS) measurements and Landsat Enhanced Thematic Mapper (ETM) image reflectance in glacial till soils with and without additional topographical information. The studied field was about 50 ha in size and located in Kalamazoo County of Michigan. The predominant soil is Kalamazoo loam (fine-loamy, mixed, mesic Typic Hapludalfs). NIRS spectra were collected along 22 north-south transects separated by a distance of 25 m and the distance between the measurements within a transect was equal to 5 m. The field was bare of vegetation and relatively dry during soil sampling. Landsat ETM imagery during soil sampling period was obtained. Eighty-five soil samples were collected on the NIRS transects from 0-10 cm depth. Principal component regression was used to relate NIRS spectra and ETM data to measured soil carbon. Regression coefficients between measured and predicted carbon values were equal to 0.70 and 0.46 using NIRS data and ETM imagery, respectively. When topographical attributes, such as elevation and terrain curvature were included into the regression model along with NIRS and ETM data, the regression coefficients improved to 0.81 and 0.62, respectively. The results indicated that combination of the NIRS and ETM measurements with topography is a valuable tool for accurate total carbon mapping in glacial till soils. Field soil moisture and texture were found to be helpful in explaining carbon variation and improving its prediction for ETM imagery data, but were not useful when added to NIRS measurements.
  • Authors:
    • Randall, G. W.
    • Lamb, J. A.
    • Clapp, C. E.
    • Allmaras, R. R.
    • Huggins, D. R.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 1
  • Year: 2007
  • Summary: Soil organic carbon (SOC) in agroecosystems is regulated by crop rotation and soil disturbance. We assessed crop sequence and tillage effects on SOC dynamics and storage using natural 13C abundance of corn (Zea mays L.) and soybean [Glycine max (L.), Merr.]. Treatments consisted of tillage: moldboard plow (MP), chisel plow (CP), and no-tillage (NT); and crop sequence: continuous corn (CC), continuous soybean (SS), and alternating corn-soybean (CS). Soil samples were collected after 14 yr in each treatment and in fallow alley-ways and were analyzed for SOC, {delta}13C, bulk density, and pH. Tillage by crop sequence interactions occurred as treatments with MP and SS as well as fallow averaged 135 Mg SOC ha-1 (0- to 45-cm depth), while CP treatments with corn (CC and CS) and NT with CC averaged 164 Mg SOC ha-1. Crop sequence effects on SOC (0- to 45-cm depth) occurred when tillage was reduced with CP and NT averaging 15% greater SOC in CC than SS. In addition to less C inputs than CC, SS accelerated rates of SOC decomposition. Tillage effects on SOC were greatest in CC where CP had 26% and NT 20% more SOC than MP, whereas SOC in SS was similar across tillage treatments. Up to 33% of the greater SOC under CC for CP and NT, compared with MP, occurred below tillage operating depths. Substantial losses of SOC were estimated (1.6 Mg SOC ha-1 yr-1) despite lowering SOC decay rates with reduced tillage and high levels of C inputs with CC.
  • Authors:
    • Chicago Climate Exchange
  • Year: 2007
  • Summary: Chicago Climate Exchange (CCX) is the world's first and North America's only active voluntary, legally binding integrated trading system to reduce emissions of all six greenhouse gases (GHGs), with Offset Projects worldwide. CCX employs independent verification and has been trading GHG emission reductions since 2003. CCX Members that cannot reduce their own emissions can purchase credits from those who make extra emission cuts or from verified Offset Projects. CCX issues tradable Carbon Financial Instrument (CFI) contracts to owners or aggregators of eligible projects on the basis of sequestration, destruction or displacement of GHG emissions. Eligible projects include: agricultural methane, landfill methane, coal mine methane, agricultural and rangeland soil carbon, forestry and renewable energy.
  • Authors:
    • Groffman, Peter M.
    • Gold, A. J.
    • Nowicki, B. L.
    • Kellogg, D. Q.
    • Addy, K.
    • Clough, T. J.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 7
  • Year: 2007
  • Summary: Few data are available to validate the Intergovernmental Panel on Climate Change's (IPCC) emission factors for indirect emissions of nitrous oxide (N2O). In particular the N2O emissions resulting from nitrogen leaching and the associated groundwater and surface drainage (EF5-g) are particularly poorly characterized. In situ push-pull methods have been used to identify the fate of NO3 in the groundwater. In this study, we adapted a previously published in situ denitrification push-pull method to examine the fate of 15N2O introduced into the subsoil-groundwater matrix. Enriched 15 N2O was manufactured, added to groundwater via a closed system in the laboratory, and then introduced into the groundwater-subsoil matrix in an upland-marsh transition zone of a salt marsh and a forested alluvial riparian zone. Conservative tracers (SF6 and Br ) and 15N2O were injected into the groundwater and left for 1-4 h after which the groundwater was sampled. Added 15N2O behaved in a conservative manner at one site while the other site showed variability with some injections showing significant consumption (38 [micro]g N2O-15 Nkg-1 soil day-1) of 15N2O. Our results show that the fate and dynamics of N2O in groundwater are complex and variable and that these dynamics should be considered in the development of improved IPCC inventory calculations.
  • Authors:
    • Dobermann, A.
    • Walters, D. T.
    • Binder, D. L.
    • Haddix, M. L.
    • Adviento-Borbe, M. A. A.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 9
  • Year: 2007
  • Summary: Crop intensification is often thought to increase greenhouse gas (GHG) emissions, but studies in which crop management is optimized to exploit crop yield potential are rare. We conducted a field study in eastern Nebraska, USA to quantify GHG emissions, changes in soil organic carbon (SOC) and the net global warming potential (GWP) in four irrigated systems: continuous maize with recommended best management practices (CC-rec) or intensive management (CC-int) and maize-soybean rotation with recommended (CS-rec) or intensive management (CS-int). Grain yields of maize and soybean were generally within 80-100% of the estimated site yield potential. Large soil surface carbon dioxide (CO2) fluxes were mostly associated with rapid crop growth, high temperature and high soil water content. Within each crop rotation, soil CO2 efflux under intensive management was not consistently higher than with recommended management. Owing to differences in residue inputs, SOC increased in the two continuous maize systems, but decreased in CS-rec or remained unchanged in CS-int. N2O emission peaks were mainly associated with high temperature and high soil water content resulting from rainfall or irrigation events, but less clearly related to soil NO3-N levels. N2O fluxes in intensively managed systems were only occasionally greater than those measured in the CC-rec and CS-rec systems. Fertilizer-induced N2O emissions ranged from 1.9% to 3.5% in 2003, from 0.8% to 1.5% in 2004 and from 0.4% to 0.5% in 2005, with no consistent differences among the four systems. All four cropping systems where net sources of GHG. However, due to increased soil C sequestration continuous maize systems had lower GWP than maize-soybean systems and intensive management did not cause a significant increase in GWP. Converting maize grain to ethanol in the two continuous maize systems resulted in a net reduction in life cycle GHG emissions of maize ethanol relative to petrol-based gasoline by 33-38%. Our study provided evidence that net GHG emissions from agricultural systems can be kept low when management is optimized toward better exploitation of the yield potential. Major components for this included (i) choosing the right combination of adopted varieties, planting date and plant population to maximize crop biomass productivity, (ii) tactical water and nitrogen (N) management decisions that contributed to high N use efficiency and avoided extreme N2O emissions, and (iii) a deep tillage and residue management approach that favored the build-up of soil organic matter from large amounts of crop residues returned.
  • Authors:
    • Guzman, J.
    • Al-Kaisi, M.
  • Source: Integrated Crop Management
  • Volume: IC-498
  • Issue: 7
  • Year: 2007