• Authors:
    • Weisskopf, P.
    • Leifeld, J.
    • Anken, T.
    • Hermle, S.
  • Source: Soil & Tillage Research
  • Volume: 98
  • Issue: 1
  • Year: 2008
  • Summary: Soil tillage and its interaction with climate change are widely discussed as a measure fostering carbon sequestration. To determine possible carbon sinks in agriculture, it is necessary to study carbon sequestration potentials in relation to agricultural management. The aim of this paper is to evaluate the soil carbon sequestration potential of a site in north-eastern Switzerland under different tillage systems. The study was performed as a long-term (19-year) trial on an Orthic Luvisol (sandy loam) with a mean annual air temperature of 8.4 °C and a long-term precipitation mean of 1183 mm. The soil organic carbon (SOC) concentration was determined five times during the study period, with the paper focussing mainly on the year 2006. The main objective was to quantify the influence of mouldboard ploughing (PL), shallow tillage (ST), no-tillage (NT) practices, and grassland (GL) on soil organic carbon content, the latter's different fractions (labile, intermediate, and stable), and its distribution by depth. In calculating the SOC content of the whole soil profile, we included a correction factor accounting for variations in bulk density (equivalent soil mass). The total SOC stock at a depth of 0-40 cm was 65 Mg C ha-1, and although higher under GL, did not differ significantly between PL, ST, and NT. SOC concentrations per soil layer were significantly greater for NT and ST (0-10 cm) than for PL, which had greater SOC concentrations than NT and ST at 20-30 cm depth. Both SOC concentrations and stocks (0-20 cm) were largest under GL. In all treatments, most of the carbon was found in the intermediate carbon fraction. There was no significant difference in any of the three SOC fractions between NT and ST, although there was between ST and PL. A sharp decrease in C-concentrations was observed in the first 7 years after the transition from grassland to arable land, with a new equilibrium of the carbon concentration in the 0-40 cm layer being reached 12 years later, with no significant difference between the tillage treatments. Overall, the results indicate that effects of tillage on soil carbon are small in moist, cold-temperate soils, challenging conversion into no-till as a measure for sequestering C.
  • Authors:
    • Grant, C. A.
    • Li, X.
    • Burton, D. L.
  • Source: Canadian Journal of Soil Science
  • Volume: 88
  • Issue: 2
  • Year: 2008
  • Summary: Fertilizer nitrogen use is estimated to be a significant source of nitrous oxide (N2O) emissions in western Canada. These estimates are based primarily on modeled data, as there are relatively few studies that provide direct measures of the magnitude of N2O emissions and the influence of N source on N2O emissions. This study examined the influence of nitrogen source (urea, coated urea, urea with urease inhibitor, and anhydrous ammonia), time of application (spring, fall) and method of application (broadcast, banded) on nitrous oxide emissions on two Black Chemozemic soils located near Winnipeg and Brandon Manitoba. The results of this 3-yr study demonstrated consistently that the rate of fertilizer-induced N2O emissions under Manitoba conditions was lower than the emissions estimated using Intergovernmental Panel on Climate Change (IPCC) coefficients. The Winnipeg site tended to have higher overall NO emissions (1.7 kg N ha(-1)) and fertilizer-induced emissions (-0.8% of applied N) than did the Brandon site (0.5 kg N ha(-1)), representing similar to 0.2% of applied N. N2O emissions in the first year of the study were much higher than in subsequent years. Both the site and year effects likely reflected differences in annual precipitation. The N2O emissions associated with the use of anhydrous ammonia as a fertilizer source were no greater than emissions with urea. Fall application of nitrogen fertilizer tended to result in marginally greater N2O emissions than did spring application, but these differences were neither large nor consistent.
  • Authors:
    • MacLeod, J. A.
    • Gillam, K. M.
    • Zebarth, B. J.
    • Burton, D. L.
  • Source: Canadian Journal of Soil Science
  • Volume: 88
  • Issue: 2
  • Year: 2008
  • Summary: The timing of fertilizer nitrogen (N) application influences the availability of NOT as a substrate for denitrification. This study examined the effect of split application of fertilizer N on N2O emissions and denitrification rate in potato (Solanum tuberosum L.) production over 2 yr. Three treatments were used: 0 or 200 kg N ha(-1) at planting, and 120 kg N ha(-1) at planting plus 80 kg N ha(-1) at final hilling. Fertilizer N application increased cumulative N2O emissions. Split fertilizer N application decreased cumulative N2O emissions in 2003, but not in 2002, compared with all fertilizer N applied at planting. A greater proportion of N2O emissions occurred between planting and hilling in 2003 (67%) compared with 2002 (17%). In 2003, the higher emissions during this period resulted from the coincidence of high soil NOT availability and increased rainfall resulting in reduced aeration. Split N application was effective in reducing N2O emissions by minimizing the supply of NOT when demand for terminal electron acceptors was high. v emissions were higher in the potato hill relative to the furrow; however, denitrification rate was higher in the furrow. Nitrate intensity (NI) expresses the exposure of the soil microbial population to NO3- and was calculated as the summation of daily soil nitrate concentration over the monitoring period. Cumulative N2O emissions were positively related to NI across year, N fertility treatment and row location. Denitrification was not related to NI, reflecting the primary role of NOT in influencing the N2O:N-2 ratio of denitrification rather than the magnitude of the overall process. Split N application was an effective strategy for reducing N2O emissions in years where there was significant rainfall during the period between planting and hilling.
  • Authors:
    • D'Ordine, R.
    • Navarro, S.
    • Back, S.
    • Fernandes, M.
    • Targolli, J.
    • Dasgupta, S.
    • Bonin, C.
    • Luethy, M. H.
    • Heard, J. E.
    • Salvador, S.
    • Kumar, G.
    • Abad, M.
    • Stoecker, M.
    • Harrison, J.
    • Anstrom, D. C.
    • Bensen, R. J.
    • Warner, D.
    • Castiglioni, P.
    • Carpenter, J. E.
  • Source: Plant Physiology
  • Volume: 147
  • Issue: 2
  • Year: 2008
  • Summary: An article about bacterial RNA chaperones conferring abiotic stress tolerance in plants and improved grain yield in maize under water-limited conditions.
  • Authors:
    • ClimateCHECK
  • Year: 2008
  • Summary: The eligibility requirements of the Nitrous Oxide Emissions Reduction Protocol (NERP) are designed according to the criteria of the Alberta Offsets System and Canada's Offset System. The scope of the NERP is limited to (1) on-farm reductions of (2) emissions associated with quantification categories fertilizer, manure, residues, and irrigation. The options for baseline scenario and baseline period are presented. The justification for the additionality or Incrementality of the comprehensive 4R N management plan is described. The projects in the NERP are: (1) compared to the baseline scenario based on emissions per unit mass of each crop; (2) based on evidence of the implementation of a 4R NITROGEN stewardship plan; (3) quantified according to the level of complexity of the BMPs; and (4) include reductions achieved by growing pulses. The key to the implementation of verifiable reduction projects under the NERP is the design of a demonstrable accurate 4R N stewardship plan, as assured by (1) general guidance in the NERP confirmed by third party verification, (2) detailed design instructions in the NERP, (3) conformity with a recommended predictive model, or (4) retaining services of an approved consulting professional. The Focus Sessions of the Consultation Workshop will finalize and approve the NERP elements recommended in the Science Discussion Document, or adapt alternative
  • Authors:
    • ClimateCHECK
  • Year: 2008
  • Summary: from summary: "The proposed Summerfallow Reduction Protocol is developed according to the ISO 14064-2 (International Standards Organization, 2006) standard as adapted in the Alberta Offset System. This Science Discussion Document provides scientific knowledge and policy framework to guide discussion and decision concerning the proposed Protocol at a Consultation Workshop.
  • 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:
    • Grainger, C.
    • McGinn, S. M
    • Beauchemin, K. A.
  • Source: WCDS Advances in Dairy Technology
  • Volume: 20
  • Year: 2008
  • Summary: Methane is produced in the rumen (called enteric methane, CH4) as part of the normal process of feed digestion. Typically, about 6 to 10% of the total gross energy consumed by the dairy cow is converted to CH4 and released via the breath. In addition, CH4 is a potent greenhouse gas that contributes to global warming. Reducing CH4 losses is an environmentally sound practice that can improve production efficiency. Our review presents some nutritional approaches that can be implemented to reduce enteric CH4 emissions from dairy cows.
  • Authors:
    • Lal, R.
    • Blanco-Canqui, H.
  • Source: Geoderma
  • Volume: 145
  • Issue: 3
  • Year: 2008
  • Summary: Crop residues are a potential source for biofuel production. Yet, impacts of removal of corn (Zea mays L.) stover and other residues as biofuel feedstocks on micro-scale soil properties affecting the behavior of the whole soil are not well understood. Data on both macro- and micro-scale soil properties under different scenarios of stover management are needed to define the threshold levels of stover removal. Previous studies on stover removal impacts on soil properties have primarily focused on macroscale properties and little or not on microscale properties. Thus, this study was designed to assess impacts of annual stover removal for 3 consecutive years at rates of 0, 25, 50, 75, and 100% on soil physical properties at the aggregate level under no-tillage (NT) continuous corn systems in a Rayne silt loam (RSL) (fine-loamy, mixed, active, mesic Typic Hapludult) with 10% slope, Celina silt loam (CSL) (fine, mixed, active, mesic Aquic Hapludalfs) with 2% slope, and Hoytville clay loam (HCL) (fine, illitic, mesic Mollic Epiaqualfs) with < 1% slope in Ohio. Aggregates were sensitive to stover removal particularly in the 0- to 10-cm soil depth. Stover removal reduced aggregate stability, tensile strength (TS), water retention (WR), and subcritical water repellency, while it increased water sorptivity but had no effect on pore-size distribution within an aggregate. The interaction of aggregate stability, strength, and subcritical water repellency with aggregate structural properties due to stover removal depended on the variable antecedent soil water conditions. The aggregate stability and strength decreased while water repellency increased with increasing water potential. Impacts of stover removal on the clayey soils were equal to or higher than those on silt loam soils. Removal at rates ≥ 25% reduced the raindrop kinetic energy (KE) required to break aggregates by 13 times at HCL, while removal at rates ≥ 50% reduced the KE by 2 to 3 times at RSL and CSL for air-dry aggregates. The KE and TS decreased with increasing soil water potentials. The TS was reduced by 10% to 30% at all water potentials at RSL, by 20% to 35% between - 0.1 and - 1.5 MPa, and by 2.2 times at - 166 MPa at CSL, and by 2 to 3 times between - 1.5 and - 166 MPa at HCL under complete stover removal. Removal of stover at rates ≥ 50% reduced subcritical water repellency by 2 to 10 times in all soils. Overall, stover removal altered micro-scale soil properties, and complete stover removal had the most detrimental effects. Based on the data from previous studies on macroscale soil properties and this study, stover removal adversely affects both macro- and micro-scale soil properties.
  • Authors:
    • Ngouajio, M.
    • Wang, G.
  • Source: Hortscience
  • Volume: 43
  • Issue: 6
  • Year: 2008
  • Summary: The effects of two cover crops [cereal rye ( Secale cereale L.) and oat ( Avena sativa L.)], four tillage systems [no tillage (NT), strip tillage (ST), conventional tillage with cover crops incorporated (CTC), and conventional tillage without cover crop (CTN)], and three pre-emergence herbicide rates (full rate, half rate, and no herbicide) on pickling cucumber ( Cucumis sativus L.) growth and production, weed populations, and the incidence of pythium fruit rot were studied. Weed infestations, cucumber establishment, and cucumber leaf chlorophyll content were similar between the rye and oat treatments. However, the oat treatment had higher cucumber fruit number and weight and a lower percentage of cucumber fruit infected with Pythium spp. compared with the rye treatment. The NT and CTC systems reduced cucumber stand and leaf chlorophyll content, but had equivalent cucumber fruit number and weight compared with CTN. The NT and ST had lower weed biomass and weed density than CTN and CTC. The NT also reduced the percentage of cucumber fruit affected with pythium compared with CTN and CTC. Reducing the pre-emergence herbicide rate by half did not affect weed control or cucumber fruit yield compared with the full rate. However, weeds escaping herbicide application were larger in the half-rate treatment. The experiments indicate that with the integration of cover crops and conservation tillage, it is possible to maintain cucumber yield while reducing both herbicide inputs (by 50%) and the incidence of fruit rot caused by Pythium spp. (by 32% to 60%).