• Authors:
    • Moravcikova, P.
    • Kuniak, L.
    • Hozova, B.
    • Gajdosova, A.
  • Source: Czech Journal of Food Sciences
  • Volume: 25
  • Issue: 6
  • Year: 2007
  • Summary: Water-insoluble beta-(1,3)-D-glucan (lichenan) was determined in 43 samples of various cereal (i.e., oats, barley, wheat, millet) and pseudocereal (i.e., buckwheat, amaranth) cultivars using a modified procedure with fungal alpha-amylase (Fermizyme P 300). The content of water-insoluble beta-glucan varied with dependence on the cereal species and cultivars. The highest content was observed in covered oat cultivars (Cyril and the new breeding cultivar PS-100), ranging from 26.7 to 28.2 g/100 g dry matter (d.m.), followed by less traditional cereals such as millet ( Panicum miliaceum), amaranth ( Amaranthus sp.), and buckwheat ( Fagopyrum) - more than 20 g/100 g d. m. A somewhat lower average content of water-insoluble beta-glucan was found in wheat - 12.7-16.2 g/100 g d. m., in spelt wheat - 8.5 g/100 g d. m., and in oats - varying between 15.3 and 18.7 g/100 g d. m.
  • Authors:
    • Emery, R.
    • Maxwell, C.
    • Manns, H.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Issue: 1/2
  • Year: 2007
  • Summary: The unique capacity of fungi to efficiently sequester carbon in aerobic conditions, presents a way to maximize OC gain in agricultural systems. Oat ( Avena sativa) was planted in the temperate climate of southern Ontario, Canada to study factors affecting soil organic carbon (OC). The plots varied with initial OC from 25 to 68 g kg -1 or with ground cover of differing decomposability (alfalfa ( Medicago sativa) growing from seed, dried oat straw, dried hay and compost) on high OC soil (60-70 g kg -1). The soil was analysed for correlation of changes in soil aggregation, moisture, OC, fungal hyphal number and length and distribution of organic matter by mass and OC in density fractions within the growing season. At harvest, soil OC and moisture were increased only in plots with ground cover. Total hyphal length was not significantly different with ground cover treatment at harvest, and did not correlate with soil aggregation and soil OC. However, the number of hyphae with >5 m diameter (primarily mycorrhizal fungi) correlated with % OC in ground cover plots while the number of hyphae
  • Authors:
    • Huang, H.
    • Blackshaw, R.
    • Mover, J.
  • Source: Canadian Journal of Plant Science
  • Volume: 87
  • Issue: 4
  • Year: 2007
  • Summary: There is a renewed interest, especially among organic growers, in using either white sweetclover ( Melilotus alba Desr.) or yellow sweetclover [ M. officinalis (L.) Lam.] as cover crops. Sweetclover cultivars and tillage practices have changed since these crops were widely used as cover crops in the first half of the 20th century. Experiments were initiated in 1999, 2000, and 2002 to compare the effect of high- and low-coumarin cultivars and crop termination methods on weed suppression, available soil N, moisture conservation and following crop yield. Weed suppression was usually more effective when sweetclover residues were left on the surface than when removed as hay. Sweetclover termination at 70% bloom was often more effective in suppressing weeds than termination at the bud stage. In the summer and fall after termination, surface residues of Yukon, a high-coumarin and drought-tolerant cultivar, reduced lamb's-quarters ( Chenopodium album L.) density by >80% compared with the no sweetclover check and essentially eliminated flixweed [ Descurainia sophia (L). Webo]. In the following spring, Yukon reduced kochia [ Kochia scoparia (L.) Schrad.] density by >80% and wild oat ( Avena fatua L.) biomass by >30% compared with the no sweetclover check. There was no difference in available N for a following crop between treatments with surface residue and cultivated fallow. Available soil moisture was about 10 mm less after the highest yielding sweetclover cultivars than after cultivated fallow, but subsequent wheat yield was not reduced. Maximum wheat yields were obtained after Yukon and Arctic sweetclover were grown as cover crops. It may be possible for organic growers to manage weeds with sweetclover in a reduced tillage system that leaves most of the plant residues on the soil surface.
  • Authors:
    • Gomezdelcampo, E.
    • Murphy, R. P.
    • Evans, J. E.
  • Source: JOURNAL OF GREAT LAKES RESEARCH
  • Volume: 33
  • Issue: SI2
  • Year: 2007
  • Summary: The Sandusky River basin, located in northwest Ohio, has been influenced by agriculture since the late-1800s. In 2003, the Ohio Environmental Protection Agency identified various tributaries of the Sandusky River as failing to meet biological water quality standards mainly due to siltation. To assess the effectiveness of best management practices (BMPs), a cutoff channel of the Sandusky River in Crawford County, Ohio was used as a unique archive of channel bed material that existed in the previous channel. Historical aerial photographs and USGS peak discharge data suggest the channel was likely abandoned between 1957 and 1964. Twelve sediment cores between 2 and 3 meters in depth were collected with a vibracore, and grain-size analyses of the cutoff channel substrate were compared to similar data collected from the modern channel. Results showed an historical fining-upward trend in the mean grain size of the coarse fraction, from gravel in the cutoff channel to sand in the modern channel, but no change in the mean grain size of the fine fraction. A series of alternative explanations were examined to elucidate this fining, including sediment storage, trends in population and crop cultivation, existence of BMPs, and sediment transport during floods. Evidence from this study strongly suggests that a shift from the cultivation of low-cover crops (hay and oats) to high-cover crops (corn and soybeans) has changed the proportion of coarse-grained to fine-grained sediment loading in this section of the Sandusky River. The results have implications both for the effectiveness of BMPs in Crawford County and possibly for Lake Erie sediment budgets.
  • Authors:
    • May, W. E.
    • Brandt, S. A.
    • Lafond, G. P.
    • Holzapfel, C. B.
    • Johnston, A. M.
  • Source: Canadian Journal of Plant Science
  • Volume: 87
  • Issue: 2
  • Year: 2007
  • Summary: Delaying nitrogen (N) applications into the growing season as a risk management tool is a concept that has received considerable attention in recent years. A 3-yr field study with spring wheat ( Triticum aestivum L.) and canola ( Brassica napus L.) was conducted at two Saskatchewan locations, Indian Head and Scott. The effects of postponing N applications for up to 30 d after seeding and several application methods were evaluated against mid-row banded urea at seeding. Liquid urea ammonium-nitrate (UAN) was applied at four separate times relative to seeding, either as an in-soil coulter band or a surface band. The surface band applications were applied either with or without the addition of 5% ammonium thiosulphate (ATS), a potential urease inhibitor. The dependent variables considered included plant density and grain yield for both crops, and grain protein in wheat. The only effect on plant density occurred in canola, where the post-seeding coulter applications slightly reduced stands compared with the other treatments. Postponing N fertilization for up to 30 d after seeding compared with N fertilization at seeding did not affect the yield of canola or protein in spring wheat, but reduced the yield of spring wheat at Indian Head in 2003, which was a very dry growing season. The coulter applications only showed a slight advantage over the surface band applications. For the surface band applications, the addition of 5% ATS did not provide a noticeable advantage over UAN alone. Canola appeared to be less sensitive to post-seeding applications than spring wheat. Deferring the entire amount of fertilizer N into the growing season appears to be a viable option but it is not without risk, especially when dry conditions are encountered.
  • Authors:
    • Warland, J.
    • von Bertoldi, P.
    • Parkin, G.
    • Jayasundara, S.
    • Barbeau, J.
    • Lee, I.
    • McLaughlin, N. L.
    • Furon, A.
    • Wagner-Riddle, C.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 8
  • Year: 2007
  • Summary: No-tillage (NT), a practice that has been shown to increase carbon sequestration in soils, has resulted in contradictory effects on nitrous oxide (N2O) emissions. Moreover, it is not clear how mitigation practices for N2O emission reduction, such as applying nitrogen (N) fertilizer according to soil N reserves and matching the time of application to crop uptake, interact with NT practices. N2O fluxes from two management systems [conventional (CP), and best management practices: NT + reduced fertilizer (BMP)] applied to a corn (Zea mays L.), soybean (Glycine max L.), winter-wheat (Triticum aestivum L.) rotation in Ontario, Canada, were measured from January 2000 to April 2005, using a micrometeorological method. The superimposition of interannual variability of weather and management resulted in mean monthly N2O fluxes ranging from - 1.9 to 61.3 g N ha(-1) day(-1). Mean annual N2O emissions over the 5-year period decreased significantly by 0.79 from 2.19 kg N ha(-1) for CP to 1.41 kg N ha(-1) for BMP. Growing season (May-October) N2O emissions were reduced on average by 0.16 kg N ha(-1) (20% of total reduction), and this decrease only occurred in the corn year of the rotation. Nongrowing season (November-April) emissions, comprised between 30% and 90% of the annual emissions, mostly due to increased N2O fluxes during soil thawing. These emissions were well correlated (r(2) = 0.90) to the accumulated degree-hours below 0 degrees C at 5 cm depth, a measure of duration and intensity of soil freezing. Soil management in BMP (NT) significantly reduced N2O emissions during thaw (80% of total reduction) by reducing soil freezing due to the insulating effects of the larger snow cover plus corn and wheat residue during winter. In conclusion, significant reductions in net greenhouse gas emissions can be obtained when NT is combined with a strategy that matches N application rate and timing to crop needs.
  • Authors:
    • Lightle, D. T.
    • Karlen, D. L.
    • Johnson, J. M. F.
    • Wilhelm, W. W.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Sustainable aboveground crop biomass harvest estimates for cellulosic ethanol production, to date, have been limited by the need for residue to control erosion. Recently, estimates of the amount of corn (Zea mays L.) stover needed to maintain soil carbon, which is responsible for favorable soil properties, were reported (5.25-12.50 Mg ha-1). These estimates indicate stover needed to maintain soil organic carbon, and thus productivity, are a greater constraint to environmentally sustainable cellulosic feedstock harvest than that needed to control water and wind erosion. An extensive effort is needed to develop advanced cropping systems that greatly expand biomass production to sustainably supply cellulosic feedstock without undermining crop and soil productivity.
  • Authors:
    • Han, X.
    • Liu, P.
    • Li, L.
    • Huang, J.
    • Sun, O.
    • Zhou, Z.
  • Source: Biogeochemistry
  • Volume: 82
  • Issue: 2
  • Year: 2007
  • Summary: Equilibrium carbon stock is the result of a balance between inputs and outflows to the pool. Changes in land-use are likely to alter such balance, resulting in different carbon stores under different land-use types in addition to the impacts of global climate change. In an agro-pastoral ecotone of Inner Mongolia, northern China, we investigated productivity and belowground carbon and nitrogen stores under six different types of land-uses, namely free grazing (FG), grazing exclusion (GE), mowing (MW), corn plantation (CP), fallow (FL), and alfalfa pasture (AP), and their impacts on litter and fine roots in semiarid grassland ecosystems. We found that there were great variations in aboveground net primary production (ANPP) across the six land-use types, with CP having markedly high ANPP; the FG had significantly reduced soil organic carbon (SOC) and nitrogen stores (SON) to 100 cm depth compared with all other types of land uses, while very little litter accumulation was found on sites of the FG and CP. The top 20 cm of soils accounted for about 80% of the root carbon and nitrogen, with very little roots being found below 50 cm. About 60% of SOC and SON were stored in the top 30 cm layer. Land-use change altered the inputs of organic matters, thus affecting SOC and SON stores accordingly; the MW and GE sites had 59 and 56% more SOC and 61% more SON than the FG. Our estimation suggested that restoring severely degraded and overgrazed grasslands could potentially increase SOC and SON stores by more than 55%; conversion from the native grasses to alfalfa could potentially double the aboveground biomass production, and further increase SOC and SON stores by more than 20%. Our study demonstrated significant carbon and nitrogen storage potential of the agro-pastoral ecotone of northern China through land-use changes and improved management in the context of mitigating global climate change.
  • Authors:
    • Paustian, K.
    • Williams, S.
    • Easter, M.
    • Breidt, F. J.
    • Ogle, S. M.
  • Source: Ecological Modelling
  • Volume: 205
  • Issue: 3-4
  • Year: 2007
  • Summary: Simulation modelling is used to estimate C sequestration associated with agricultural management for purposes of greenhouse gas mitigation. Models are not completely accurate or precise estimators of C pools, however, due to insufficient knowledge and imperfect conceptualizations about ecosystem processes, leading to uncertainty in the results. It can be difficult to quantify the uncertainty using traditional error propagation techniques, such as Monte Carlo Analyses, because of the structural complexity of simulation models. Empirically based methods provide an alternative to the error propagation techniques, and our objective was to apply this alternative approach. Specifically, we developed a linear mixed-effect model to quantify both bias and variance in modeled soil C stocks that were estimated using the Century ecosystem simulation model. The statistical analysis was based on measurements from 47 agricultural experiments. A significant relationship was found between model results and measurements although there were biases and imprecision in the modeled estimates. Century under-estimated soil C stocks for several management practices, including organic amendments, no-till adoption, and inclusion of hay or pasture in rotation with annual crops. Century also over-estimated the impact of N fertilization on soil C stocks. For lands set-aside from agricultural production, Century under-estimated soil C stocks on low carbon soils and over-estimated the stocks on high carbon soils. Using an empirically based approach allows for simulation model results to be adjusted for biases as well as quantify the variance associated with modeled estimates, according to the measured "reality" of management impacts from a network of experimental sites.
  • Authors:
    • Gal, A.
    • Hegymegi, P.
    • Smith, D. R.
    • Vyn, T. J.
    • Omonode, R.A.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1-2
  • Year: 2007
  • Summary: Although the Midwestern United States is one of the world's major agricultural production areas, few studies have assessed the effects of the region's predominant tillage and rotation practices on greenhouse gas emissions from the soil surface. Our objectives were to (a) assess short-term chisel (CP) and moldboard plow (MP) effects on soil CO2 and CH4 fluxes relative to no-till (NT) and, (b) determine how tillage and rotation interactions affect seasonal gas emissions in continuous corn and corn-soybean rotations on a poorly drained Chalmers silty clay loam (Typic Endoaquoll) in Indiana.