• 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:
    • Sherlock, R. R.
    • Kelliher, F. M.
    • Buckthought, L. E.
    • Clough, T. J.
  • Source: Global Change Biology
  • Volume: 13
  • Year: 2007
  • Summary: There is uncertainty in the estimates of indirect nitrous oxide (N2O) emissions as defined by the Intergovernmental Panel on Climate Change (IPCC). The uncertainty is due to the challenge and dearth of in situ measurements. Recent work in a subtropical stream system has shown the potential for diurnal variability to influence the downstream N transfer, N form, and estimates of in-stream N2O production. Studies in temperate stream systems have also shown diurnal changes in stream chemistry. The objectives of this study were to measure N2O fluxes and dissolved N2O concentrations from a spring-fed temperate river to determine if diurnal cycles were occurring. The study was performed during a 72 h period, over a 180m reach, using headspace chamber methodology. Significant diurnal cycles were observed in radiation, river temperature and chemistry including dissolved N2O-N concentrations. These data were used to further assess the IPCC methodology and experimental methodology used. River NO3-N and N2O-N concentrations averaged 3.0mg L-1 and 1.6 lgL-1, respectively, with N2O saturation reaching a maximum of 664%. The N2O-N fluxes, measured using chamber methodology, ranged from 52 to 140 lgm-2 h-1 while fluxes predicted using the dissolved N2O concentration ranged from 13 to 25 lgm-2 h-1. The headspace chamber methodology may have enhanced the measured N2O flux and this is discussed. Diurnal cycles in N2O% saturation were not large enough to influence downstream N transfer or N form with variability in measured N2O fluxes greater and more significant than diurnal variability in N2O% saturation. The measured N2O fluxes, extrapolated over the study reach area, represented only 6104 % of the NO3-N that passed through the study reach over a 72 h period. This is only 0.1% of the IPCC calculated flux.
  • Authors:
    • Mielniczuk, J.
    • Vieira, F.
    • Dieckow, J.
    • Bayer, C.
    • Zanatta, J.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat+vetch/maize+cowpea (OV/MC)] and N fertilization [0 kg N ha -1 year -1 (0 N) and 180 kg N ha -1 year -1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0-5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0-20 cm layer varied from 0.09 to 0.34 Mg ha -1 year -1 in CT and from 0.19 to 0.65 Mg ha -1 year-1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.
  • Authors:
    • Hons, F.
    • Wright, A.
    • Dou, F.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Crop management practices have potential to enhance subsoil C and N sequestration in the southern U.S., but effects may vary with tillage regime and cropping sequence. The objective of this study was to determine the impacts of tillage and soyabean cropping sequence on the depth distribution of soil organic C (SOC), dissolved organic C (DOC), and total N after 20 years of treatment imposition for a silty clay loam soil in central Texas. A continuous soyabean monoculture, a wheat-soybean doublecrop, and a sorghum-wheat-soybean rotation were established under both conventional (CT) and no tillage (NT). Soil was sampled after soyabean harvest and sectioned into 0-5, 5-15, 15-30, 30-55, 55-80, and 80-105 cm depth intervals. Both tillage and cropping intensity influenced C and N dynamics in surface and subsurface soils. No tillage increased SOC, DOC, and total N compared to CT to a 30 cm depth for continuous soyabean, but to 55 cm depths for the more intensive sorghum-wheat-soybean rotation and wheat-soybean doublecrop. Averaged from 0 to 105 cm, NT increased SOC, DOC, and total N by 32, 22, and 34%, respectively, compared to CT. Intensive cropping increased SOC and total N at depths to 55 cm compared to continuous soyabean, regardless of tillage regime. Continuous soyabean had significantly lower SOC (5.3 g kg -1) than sorghum-wheat-soybean (6.4 g kg -1) and wheat-soybean (6.1 g kg -1), and 19% lower total N than other cropping sequences. Dissolved organic C was also significantly higher for sorghum-wheat-soybean (139 mg C kg -1) than wheat-soybean (92 mg C kg -1) and continuous soyabean (100 mg C kg -1). The depth distribution of SOC, DOC, and total N indicated treatment effects below the maximum tillage depth (25 cm), suggesting that roots, or translocation of dissolved organic matter from surface soils, contributed to higher soil organic matter levels under NT than CT in subsurface soils. High-intensity cropping sequences, coupled with NT, resulted in the highest soil organic matter levels, demonstrating potential for C and N sequestration for subsurface soils in the southern U.S.
  • Authors:
    • Molgaard, J. P.
    • Rasmussen, J.
    • Henriksen, C. B.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 1
  • Year: 2007
  • Summary: Field experiments were conducted on sand and sandy loam from 2000 to 2002 to determine how timing of ridging affects potato tuber yield and quality depending on soil texture and the use of catch crops. On sand, ridging in winter increased soil N availability in the 0-50 cm soil layer in spring from 5.7 to 6.8 mg N kg(-1) soil (19%) compared with ridging in autumn (P
  • Authors:
    • Pals, A.
    • De Baets, S.
    • Galindo-Morales, P.
    • Poesen, J.
    • Knapen, A.
  • Source: Earth Surface Processes and Landforms
  • Volume: 32
  • Issue: 12
  • Year: 2007
  • Summary: Several studies illustrate the wind and water erosion-reducing potential of semi-permanent microbiotic soil crusts in arid and semi-arid desert environments. In contrast, little is hitherto known on these biological crusts on cropland soils in temperate environments where they are annually destroyed by tillage and quickly regenerate thereafter. This study attempts to fill the research gap through (a) a field survey assessing the occurrence of biological soil crusts on loess-derived soils in central Belgium in space and time and (b) laboratory flume (2 m long) experiments simulating concentrated runoff on undisturbed topsoil samples (0.4 x 0.1 m(2)) quantifying the microbiotic crust effect on soil erosion rates. Three stages of microbiotic crust development on cropland soils are distinguished: (1) development of a non-biological surface seal by raindrop impact, (2) colonization of the soil by algae and gradual development of a continuous algal mat and (3) establishment of a well-developed microbiotic crust with moss plants as the dominant life-form. As the silt loam soils in the study area seal quickly after tillage, microbiotic soil crusts are more or less present during a large part of the year under maize, sugar beet and wheat, representing the main cropland area. On average, the early-successional algae-dominated crusts of stage 2 reduce soil detachment rates by 37%, whereas the well-developed moss mat of stage 3 causes an average reduction of 79%. Relative soil detachment rates of soil surfaces with microbiotic crusts compared with bare sealed soil surfaces are shown to decrease exponentially with increasing microbiotic cover (b = 0 center dot 024 for moss-dominated and b = 0 center dot 006 for algae-dominated crusts). In addition to ground surface cover by vegetation and crop residues, microbiotic crust occurrence can therefore not be neglected when modelling small-scale spatial and temporal variations in soil loss by concentrated flow erosion on cropland soils in temperate environments. Copyright (C) 2007 John Wiley & Sons, Ltd.
  • Authors:
    • Burmester, C.
    • Reeves, D. W.
    • Motta, A. C. V.
    • Feng, Y.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 38
  • Issue: 19-20
  • Year: 2007
  • Summary: The impact of conservation tillage, crop rotation, and cover cropping on soil-quality indicators was evaluated in a long-term experiment for cotton. Compared to conventional-tillage cotton, other treatments had 3.4 to 7.7 Mg ha(-1) more carbon (C) over all soil depths. The particulate organic matter C (POMc) accounts for 29 to 48 and 16 to 22% of soil organic C (SOC) for the 0- to 3- and 3- to 6-cm depths, respectively. Tillage had a strongth influence on POMc within the 0- to 3-cm depth, but cropping intensity and cover crop did not affect POW A large stratification for microbial biomass was observed varing from 221 to 434 and 63 to 110 mg kg(-1) within depth of 0-3 and 12-24 cm respectively. The microbial biomass is a more sensitive indicator (compared to SOC) of management impacts, showing clear effect of tillage, rotation, and cropping intensity. The no-tillage cotton double-cropped wheat/soybean system that combined high cropping intensity and crop rotation provided the best soil quality.
  • Authors:
    • Labreuche, J.
    • Thiébeau, P.
    • Mary, B.
    • Laurent, F.
    • Oorts, K.
    • Nicolardot, B.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Soil N mineralization was quantified in two long-term experiments in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated for 33 years (Site 1) and 12 years (Site 2). Both sites had the same soil type but differed in crop rotation. N mineralization kinetics were assessed in situ in bare soil in both systems for 254 days (Site 1) and 555 days (Site 2) by taking frequent measurements of water and nitrate contents from soil layers and using the LIXIM calculation model. The N mineralization potential was also determined in soil samples incubated under controlled laboratory conditions. Small or non-significant differences in water and nitrate contents between NT and CT were apparent within the soil profiles on both sites. Net mineralization did not differ significantly between sites or tillage treatments. The amount of N mineralized from August 2003 to April 2004 was 6710 kg N ha -1 on Site 1 and 745 kg N ha -1 on Site 2, and 1616 kg N ha -1 from August 2003 to February 2005 on Site 2. The kinetics of N mineralization versus normalized time (equivalent time at constant temperature of 15degreesC and water content at field capacity) were linear during the shorter period (254 days corresponding to 120 normalized days). The slope (N mineralization rate) did not differ significantly between treatments and sites, and the average rate was 0.570.05 kg N ha -1 nd -1. The kinetics were non-linear on Site 2 over the longer period (555 days corresponding to 350 normalized days). They could be fitted to an exponential model with a slope at the origin of 0.62 kg N ha -1 nd -1. The N mineralization kinetics obtained in laboratory incubations for 120-150 normalized days were also almost linear with no significant differences between treatments. Assuming that mineralization took place in the ploughed layer (in CT) or over the same soil mass (in NT) they were in good agreement with the kinetics determined in situ on both sites. The calculated water drainage below the sampled profile was slightly greater in NT due to lower evaporation. The calculated leached N was slightly higher in NT than CT on Site 1, but did not differ between treatments on Site 2. It is concluded that N mineralization and leaching in NT and CT were similar, despite large differences in N distribution within the soil profile and a slight difference in organic N stock.
  • Authors:
    • Labreuche, J.
    • Gréhan, E.
    • Merckx, R.
    • Oorts, K.
    • Nicolardot, B.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1/2
  • Year: 2007
  • Summary: The greenhouse gases CO 2 and N 2O emissions were quantified in a long-term experiment in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated during 32 years in plots under a maize-wheat rotation. Continuous CO 2 and periodical N 2O soil emission measurements were performed during two periods: under maize cultivation (April 2003-July 2003) and during the fallow period after wheat harvest (August 2003-March 2004). In order to document the dynamics and importance of these emissions, soil organic C and mineral N, residue decomposition, soil potential for CO 2 emission and climatic data were measured. CO 2 emissions were significantly larger in NT on 53% and in CT on 6% of the days. From April to July 2003 and from November 2003 to March 2004, the cumulated CO 2 emissions did not differ significantly between CT and NT. However, the cumulated CO 2 emissions from August to November 2003 were considerably larger for NT than for CT. Over the entire 331 days of measurement, CT and NT emitted 3160269 and 4064138 kg CO 2-C ha -1, respectively. The differences in CO 2 emissions in the two tillage systems resulted from the soil climatic conditions and the amounts and location of crop residues and SOM. A large proportion of the CO 2 emissions in NT over the entire measurement period was probably due to the decomposition of old weathered residues. NT tended to emit more N 2O than CT over the entire measurement period. However differences were statistically significant in only half of the cases due to important variability. N 2O emissions were generally less than 5 g N ha -1 day -1, except for a few dates where emission increased up to 21 g N ha -1 day -1. These N 2O fluxes represented 0.800.15 and 1.320.52 kg N 2O-N ha -1 year -1 for CT and NT, respectively. Depending on the periods, a large part of the N 2O emissions occurred was probably induced by nitrification, since soil conditions were not favorable for denitrification. Finally, for the period of measurement after 32 years of tillage treatments, the NT system emitted more greenhouses gases (CO 2 and N 2O) to the atmosphere on an annual basis than the CT system.
  • Authors:
    • McGawley, E. C.
    • Pontif, M. J.
  • Source: Nematropica
  • Volume: 37
  • Issue: 2
  • Year: 2007
  • Summary: Reniform nematodes that parasitize cotton and soybean can also reproduce on a wide spectrum of weed species, thereby maintaining nematode populations during the off-season. Microplot studies were conducted to evaluate the effects of three endemic weed species, morningglory ( Ipomoea lacunosa), hemp sesbania ( Sesbania exaltata), and johnsongrass ( Sorghum halepense), on reproduction of the reniform nematode, Rotylenchulus reniformison cotton (LA. 887) and soybean (Pioneer 96B21). Over two years of microplot trials, the co-culture of cotton with any of the three weed species suppressed numbers of reniform nematode juveniles in soil significantly. When grown singly, reproductive values of R. reniformis after 60 days on cotton averaged 69.0, while those for morningglory, hemp sesbania, and johnsongrass averaged 42.0, 23.5, and 18.0, respectively. Reproductive values on cotton co-cultured with morningglory averaged 38.5. Those for the cotton-hemp sesbania and cotton-johnsongrass combinations averaged 23.5 and 26.0, respectively. Nematode reproduction on soybean alone, and co-cultured with each of the three weeds, reduced reproduction of reniform nematode only in the presence of johnsongrass in two trials. Data from two subsequent 45-day duration greenhouse experiments conducted with cotton and leachates from each of the three weed species support the hypothesis that suppression of reniform nematode reproduction likely resulted from the secretion of allelopathic compounds by weed roots.