• Authors:
    • Laird, D. A.
  • 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:
    • Williams, A.
    • Moxey, A.
    • Rees, B.
    • Barnes, A.
    • McVittie, A.
    • Matthews, R.
    • Pajot, G.
    • Eory, V.
    • Wall, E.
    • MacLeod, M.
    • Moran, D.
  • Year: 2008
  • Authors:
    • Fuller, R. J.
    • Blain, A.
    • Smart, S.
    • Petit, S.
    • Firbank, L. G.
  • Source: Philosophical Transactions of The Royal Society B: biological Sciences
  • Volume: 363
  • Issue: 1492
  • Year: 2008
  • Summary: Agricultural intensification is best considered as the level of human appropriation of terrestrial net primary production. The global value is set to increase from 30%, increasing pressures on biodiversity. The pressures can be classified in terms of spatial scale, i.e. land cover, landscape management and crop management. Different lowland agricultural landscapes in Great Britain show differences among these pressures when habitat diversity and nutrient surplus are used as indicators. Eutrophication of plants was correlated to N surplus, and species richness of plants correlated with broad habitat diversity. Bird species diversity only correlated with habitat diversity when the diversity of different agricultural habitats was taken into account. The pressures of agricultural change may be reduced by minimizing loss of large habitats, minimizing permanent loss of agricultural land, maintaining habitat diversity in agricultural landscapes in order to provide ecosystem services, and minimizing pollution from nutrients and pesticides from the crops themselves. While these pressures could potentially be quantified using an internationally consistent set of indicators, their impacts would need to be assessed using a much larger number of locally applicable biodiversity indicators.
  • Authors:
    • Lehmann, J.
    • Gaunt, J. L.
  • Source: Environmental Science & Technology
  • Volume: 42
  • Issue: 11
  • Year: 2008
  • Summary: Compared to its use as an energy source biochar produced by slow pyrolysis is more effective in reducing greenhouse gas emissions when used as a soil conditioner.
  • Authors:
    • Paton, R. J.
    • Morton, J. D.
    • Littlejohn, R. P.
    • Houlbrooke, D. J.
  • Source: Soil Use and Management
  • Volume: 24
  • Issue: 4
  • Year: 2008
  • Summary: The North Otago Rolling Downlands (NORD) of New Zealand is currently undergoing a large change in land use with subsequent intensification as a result of a new large community irrigation scheme. To assess the effect of this change, a 4-year monitoring survey was established on two common Pallic soil types of the area to determine the influence of irrigation term (short, 5 years) and grazing animal (cattle vs. sheep) on a range of physical and organic matter soil quality parameters. This 4-year survey also included the historical land use of dryland sheep farming in the absence of irrigation water. Irrigation term had no significant (P > 0.05) effect on soil physical parameters (percentage macroporosity and bulk density) for 3 of 4 years and no significant effect (P > 0.05) on topsoil total carbon or nitrogen contents. However, irrigation term had a significant (P < 0.01) but biologically small effect on the ratio of carbon to nitrogen with narrowing of the range under longer term irrigation. A significant difference between the dryland and irrigated surveys was found for macroporosity (dryland sheep 17.3% v/v vs. irrigated sheep 13.4% v/v; P < 0.001) and for the C:N ratio (dryland sheep 10.7 vs. irrigated sheep 10.2; P < 0.05). The change in macroporosity under irrigation is likely to take effect within 1 or 2 years of land-use change as little discernable differences in soil physical properties were evident from land under short- or long-term irrigation.
  • Authors:
    • Eriksen-Hamel, N. S.
    • Angers, D. A.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 5
  • Year: 2008
  • Summary: While the adoption of no-till (NT) usually leads to the accumulation of soil organic C (SOC) in the surface soil layers, a number of studies have shown that this effect is sometimes partly or completely offset by greater SOC content near the bottom of the plow layer under full-inversion tillage (FIT). Our purpose was to review the literature in which SOC profiles have been measured under paired NT and FIT situations. Only replicated and randomized studies directly comparing NT and FIT for >5 yr were considered. Profiles of SOC had to be measured to at least 30 cm. As expected, in most studies SOC content was significantly greater (P < 0.05) under NT than FIT in the surface soil layers. At the 21- to 25-cm soil depth, however, which corresponds to the mean plowing depth for the data set (23 cm), the average SOC content was significantly greater under FIT than NT. Moreover, under FIT, greater SOC content was observed just below the average depth of plowing (26-35 cm). On average, there was 4.9 Mg ha(-1) more SOC under NT than FIT (P = 0.03). Overall, this difference in favor of NT increased significantly but weakly with the duration of the experiment (R-2 = 0.15, P = 0.05). The relative accumulation of SOC at depth under FIT could not be related to soil or climatic variables. Furthermore, the organic matter accumulating at depth under FIT appeared to be present in relatively stable form, but this hypothesis and the mechanisms involved require further investigation.
  • Authors:
    • Van Cleemput, O.
    • Ahmed, H. P.
    • Boeckx, P.
    • Beheydt, D.
  • Source: Biology and Fertility of Soils
  • Volume: 44
  • Issue: 6
  • Year: 2008
  • Summary: In this study, we investigated N2O emissions from two fields under minimum tillage, cropped with maize (MT maize) and summer oats (MT oats), and a conventionally tilled field cropped with maize (CT maize). Nitrous oxide losses from the MT maize and MT oats fields (5.27 and 3.64 kg N2O-N ha(-1), respectively) were significantly higher than those from the CT maize field (0.27 kg N2O-N ha(-1)) over a period of 1 year. The lower moisture content in CT maize (43% water-filled pore space [WFPS] compared to 60 -65%) probably caused the difference in total N2O emissions. Denitrification was found to be the major source of N2O loss. Emission factors calculated from the MT field data were high (0.04) compared to the CT field (0.001). All data were simulated with the denitrification decomposition model (DNDC). For the CT field, N2O and N2O+N-2 emissions were largely overestimated. For the MT fields, there was a better agreement with the total N2O and N2O+N-2 emissions, although the N2O emissions from the MT maize field were underestimated. The simulated N2O emissions were particularly influenced by fertilization, but several other measured N2O emission peaks associated with other management practices at higher WFPS were not captured by the model. Several mismatches between simulated and measured NH4+, NO3-and WFPS for all fields were observed. These mismatches together with the insensitivity of the DNDC model for increased N2O emissions at the management practices different from fertilizer application explain the limited similarity between the simulated and measured N2O emissions pattern from the MT fields.
  • Authors:
    • Durigan, J.
    • Correia, N.
  • Source: Bioscience Journal
  • Volume: 24
  • Issue: 4
  • Year: 2008
  • Summary: To evaluate the effect of cover crops [sorghum ( Sorghum bicolor 'Sara'), coverage sorghum ( S. bicolor * S. sudanensis 'Cober Exp'), forage millet ( Pennisetum americanum 'BN2'), common millet ( Pennisetum americanum), finger millet ( Eleusine coracana) and St. Lucia Grass ( Brachiaria brizantha)] and treatment with spontaneous vegetation, in soil fertility after two years under no-tillage systems, experiment was conducted at the farm 'Tres Marcos', Uberlandia, MG - Brazil. The soil was collected in February 2005, after the harvest of the soybean grains (cv. M-SOY 6101), in depths of 0-5 cm, 5-10 cm and 10-20 cm. The coverage resulted in soil chemical properties alteration, with different responses at the sampling depths studied. In first 5 cm of soil, was observed higher pH, organic matter, exchangeable Ca and Mg, base saturation, bases content and effective cation exchange capacity than in deeper samples. The soil kept with spontaneous vegetation showed the highest pH, Ca and Mg levels, base saturation and effective cation exchange capacity, while the soil under cover crop showed higher P and organic matter levels.
  • Authors:
    • Aitken, S. N.
    • Yanchuk, A. D.
    • Gapare, W. J.
  • Source: Conservation Genetics
  • Volume: 9
  • Issue: 2
  • Year: 2008
  • Summary: In previous studies we reported that while core populations of Sitka spruce [Picea sitchensis (Bong.) Carr] have little within-population genetic structure, peripheral populations are strongly spatially structured at distances up to 500 m. Here we explore the implications of this difference in structure on ex situ gene conservation collections and estimates of genetic diversity from research collections. We test the effects of varying the number of individuals sampled and the total area they are sampled across on capture of neutral genetic variation in collections from core, continuous versus peripheral, disjunct populations. Bivariate response surface analysis of genetic marker data for eight sequence tagged site loci from core and peripheral populations suggest that a population sample from 150 trees covering at least 225 ha would be adequate for capturing 95% of the genetic diversity (as measured by allelic richness or expected heterozygosity) in core populations. However, a larger sample of 180 individuals from an area of at least 324 ha is needed in peripheral populations to capture the same proportion of standing variation because of stronger within-population spatial genetic structure. Standard population sampling protocols for estimating among and within-population genetic diversity would significantly underestimate the within-population allelic richness and expected heterozygosity of peripheral but not core populations, potentially leading to poor representation of genetic variation in peripheral populations as well as erroneous conclusions about their genetic impoverishment.
  • Authors:
    • Claupein, W.
    • Lewandowski, I.
    • Boehmel, C.
  • Source: Agricultural Systems
  • Volume: 96
  • Issue: 1/3
  • Year: 2008
  • Summary: Given the political targets, it can be expected that in Europe, energy production from agricultural land will increase and that improved systems for its production are needed. Therefore, a four year field trial was conducted on one site in south-western Germany to compare and evaluate the biomass and energy yield performance of important energy crops. Six energy cropping systems with the potential to produce biomass for first and second-generation biofuels were selected. The systems were short rotation willow coppice, miscanthus, switchgrass, energy maize and two different crop rotation systems including winter oilseed rape, winter wheat and winter triticale. The two crop rotation systems were managed in either conventional tillage or no-till soil cultivation systems. The second test parameter was three different crop-specific nitrogen application levels. The performance of the energy cropping systems was evaluated by measuring the biomass yields and calculating the energy yields, as well as through an energy balance and nitrogen budget. Results show the superiority of the annual energy crop maize in dry matter yield (DMY) and primary net energy yield (PNEY=difference between the primary energy yield (DMY * lower heating value) and the energy consumption) performance with peak values at the highest N-application level of 19.1 t DM ha -1 a -1 and 350 GJ ha -1 a -1, respectively. The highest yielding perennial crop was miscanthus with 18.1 t ha -1 a -1 DMY and a PNEY of 277 GJ ha -1 a -1, followed by willow with 15.2 t ha -1 a -1 and 258 GJ ha -1 a -1, at the highest N-application level. Switchgrass showed the lowest yields of the perennial crops with 14.1 t ha -1 a -1 DMY at the highest N-application level. The yields of the two crop rotation systems did not differ significantly and amounted to 14.6 t ha -1 a -1 DMY of both grain and straw at the highest N-application level. Willow showed the significantly highest energy use efficiency (output (PNEY):input (energy consumption)-ratio) with 99 GJ energy output per GJ fossil energy input at the lowest N-application level (no fertilizer). The two crop rotation systems had the lowest energy use efficiency with 20 GJ GJ -1 for the production of total aboveground biomass. Energy maize gave the best energy yield performance but at a relatively high energy input, whereas willow and miscanthus as perennial energy crops combine high yields with low inputs. Results suggest that no-till systems had no negative impact on biomass and energy yields, but that there was also no positive impact on energy saving.