• 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:
    • Mora, G.
    • Helmers, M.
    • Shepherd, G.
    • Asbjornsen, H.
  • Source: Plant and Soil
  • Volume: 308
  • Issue: 1-2
  • Year: 2008
  • Summary: In agricultural landscapes, variation and ecological plasticity in depth of water uptake by annual and perennial plants is an important means by which vegetation controls hydrological balance. However, little is known about how annual and perennial plants growing in agriculturally dominated landscapes in temperate humid regions vary in their water uptake dynamics. The primary objective of this study was to quantify the depth of water uptake by dominant plant species and functional groups growing in contrasting annual and perennial systems in an agricultural landscape in Central Iowa. We used stable oxygen isotope techniques to determine isotopic signatures of soil water and plant tissue to infer depth of water uptake at five sampling times over the course of an entire growing season. Our results suggest that herbaceous species (Zea mays L., Glycine max L. Merr., Carex sp., Andropogon gerardii Vitman.) utilized water predominantly from the upper 20 cm of the soil profile and exhibited a relatively low range of ecological plasticity for depth of water uptake. In contrast, the woody shrub (Symphoricarpos orbiculatus Moench.) and tree (Quercus alba L.) progressively increased their depth of water uptake during the growing season as water became less available, and showed a high degree of responsiveness of water uptake depth to changes in precipitation patterns. Coexisting shrubs and trees in the woodland and savanna sites extracted water from different depths in the soil profile, indicating complementarity in water uptake patterns. We suggest that deep water uptake by perennial plants growing in landscapes dominated by rowcrop agriculture can enhance hydrologic functioning. However, because the high degree of ecological plasticity allows some deep-rooted species to extract water from surface horizons when it is available, positive effects of deep water uptake may vary depending on species' growth patterns and water uptake dynamics. Knowledge about individual species' and plant communities' depth of water uptake patterns in relation to local climate conditions and landscape positions can provide valuable information for strategically incorporating perennial plants into agricultural landscapes to enhance hydrologic regulation.
  • 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:
    • Lal, R.
    • Blanco-Canqui, H.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 3
  • Year: 2008
  • Summary: No-tillage (NT) farming is superior to intensive tillage for conserving soil and water, yet its potential for sequestering soil organic carbon (SOC) in all environments as well as its impacts on soil profile SOC distribution are not well understood. Thus, we assessed the impacts of long-term NT-based cropping systems on SOC sequestration for the whole soil profile (0-60-cm soil depth) across 11 Major Land Resource Areas (MLRAs: 121, 122, and 125 in Kentucky; 99, 124, 139A in Ohio; and 139B, 139C, 140, 147, and 148 in Pennsylvania) in the eastern United States. Soil was sampled in paired NT and plow tillage (PT) based cropping systems and an adjacent woodlot (WL). No-tillage farming impacts on SOC and N were soil specific. The SOC and N concentrations in NT soils were greater than those in PT soils in 5 out of 11 MLRAs (121, 122, 124, 139A, and 148), but only within the 0- to 10-cm depth. Below 10 cm, NT soils had lower SOC than PT soils in MLRA 124. The total SOC with NT for the whole soil profile (0-60 cm) did not differ from that with PT (P > 0.10) in accord with several previous studies. In fact, total soil profile SOC in PT soils was 50% higher in MLRA 125, 21% in MLRA 99, and 41% in MLRA 124 compared with that in NT soils. Overall, this study shows that NT farming increases SOC concentrations in the upper layers of some soils, but it does not store SOC more than PT soils for the whole soil profile.
  • Authors:
    • Sweeney, D.
    • Kelley, K.
  • Source: Crop Management
  • Issue: November
  • Year: 2008
  • Summary: Field studies were conducted from 1999 through 2004 in southeastern Kansas to evaluate the influence of tillage method [conventional (CT) and no-till (NT)], row spacing-population system (7.5-, 15-, and 30-inch rows planted at 225,000, 175,000, and 125,000 seeds/acre, respectively), and glyphosate application timing on soybean [ Glycine max (L.) Merr.] yield, weed control, and net economic returns. Herbicide treatments were: (i) preplant residual (pendimethalin) followed by glyphosate at 3 weeks after planting (WAP); (ii) glyphosate at 3 WAP; (iii) sequential glyphosate at 3 and 5 WAP; and (iv) glyphosate at 8 WAP. Soybean followed grain sorghum [ Sorghum bicolor (L.) Moench] in a 2-year rotation. Tillage method influenced yield very little. Narrower row spacing (7.5- and 15-inch) increased soybean yields 2 to 4 bu/acre in high-yielding environments compared to 30-inch rows and also provided greater weed control. Glyphosate applied sequentially (3 and 5 WAP) provided the highest weed control, but a single glyphosate application 3 WAP often produced the greatest net return, regardless of tillage or row spacing system. The results suggest that the adoption of NT planting will likely increase soybean net returns to a greater extent than reducing row spacing in the eastern Great Plains.
  • Authors:
    • Pierzynski, G.
    • Tuppad, P.
    • Janssen, K.
    • Mankin, K.
    • Maski, D.
  • Source: Journal of Soil and Water Conservation
  • Volume: 63
  • Issue: 4
  • Year: 2008
  • Summary: Cropland best management practice recommendations often combine improvements to both tillage and fertilizer application practices to reduce sediment losses with surface runoff. This study evaluated the impact of conventional-till and no-till management practices with surface or deep-banded fertilizer application in sorghum-soybean rotation on runoff and sediment-yield predictions using the Soil and Water Assessment Tool (SWAT) model. The model was calibrated using USDA Natural Resources Conservation Service runoff curve number for antecedent moisture condition II (CN II), saturated hydraulic conductivity, and available water capacity parameters for runoff and USLE cropping factor ( Cmin.) for sediment-yield predictions for three field plots (0.39 to 1.46 ha [0.96 to 3.6 ac]) with different combinations of practices and validated for three field plots (0.40 to 0.56 ha [1.0 to 1.4 ac]) over a period of 2000 to 2004. Surface runoff calibration required CN II values greater than the recommended baseline values. No-till treatments required slightly greater curve number values than the till treatment, and this difference was similar to that associated with increasing the soil hydrologic group by one classification. Generally the model underpredicted the sediment yield for all management practices. Baseline Cmin values were adequate for treatments with soil disturbance, either by tillage or fertilizer deep-banding, but best-fit Cmin values for field conditions without soil disturbance (no-till with surface-broadcast fertilizer) were 2.5 to 3 times greater than baseline values. These results indicate current model limitations in modeling undisturbed (no-till) field management conditions, and caution that models calibrated for fields or watersheds predominated by tilled soil conditions may not function equally well in testing management scenarios without tillage.
  • Authors:
    • Humburg, D. S.
    • Schumacher, T. E.
    • Osborne, S. L.
  • Source: Agricultural Journal
  • Volume: 3
  • Issue: 5
  • Year: 2008
  • Summary: Although no-till soil management has many benefits, including protecting the soil from erosion, improving soil organic matter and improving soil moisture storage, depending on environmental conditions there could be a number of potential problems. Implementation of no-till soil management in eastern South Dakota can lead to wet and cold soils at the time of planting. Cover crops have the potential to utilize excess soil moisture and improve soil conditions at planting. A field experiment was established to evaluate the impact of 14 different cover crop species as well as no cover crop and conventional tillage on soil conditions prior to corn planting and the impact on corn yield and quality. The experimental design was a randomized complete block design with 4 replications. Cover crops evaluated include a mixture of grass, legumes, cool and warm season crops. All cover crops were planted in early August (following spring wheat harvest) at recommended seeding rates. The following spring all plots were planted to corn ( Zea mays L.). The experiment was conducted in a 3 year crop rotation (soybean [ Glycine max (L.) Merrill]/spring wheat ( Triticum aestivum L.)-cover crop/corn). Cover crop species that survived the winter included hairy vetch, red clover, sweet clover, Alsike clover, slender wheatgrass and winter ryegrass. The presence of these species increased soil strength and reduced soil moisture. Corn grown following hairy vetch was the only treatment that exhibited a significant reduction in plant population. Corn yield for plots grown under red clover, winter ryegrass and no cover crop had yield significantly higher than corn grown after conventional tillage, hairy vetch and slender wheatgrass. This experiment illustrated the ability of cover crops to utilize excess soil moisture and increase soil strength compared to conventional tillage or no cover crop.
  • Authors:
    • Cassman, K. G.
    • Specht, J. E.
    • Weiss, A.
    • Setiyono, T. D.
    • Dobermann, A.
  • Source: Field Crops Research
  • Volume: 108
  • Issue: 1
  • Year: 2008
  • Summary: Different approaches have been used to simulate leaf area index (LAI) in soybean ( Glycine max L. Merr). Many of these approaches require genotype-specific calibration procedures. Studies modeling LAI dynamics under optimal growth conditions with yields close to the yield potential of soybean have remained scarce. A sink-driven approach was developed and evaluated for LAI simulation in soybean under near-optimal environments. The rate of change in expanding leaf area was simulated using the first derivative of a logistic function accounting for plant population density, air temperature, and water deficit. The rate of change in senescing leaf area was also simulated using the first derivative of a logistic function, assuming monocarpic senescence that began at the flowering stage (R1). Phenology was simulated as a function of temperature and photoperiod. Data for model development and evaluation were obtained from irrigated field experiments conducted at two locations in Nebraska, where agronomic management was optimized to achieve growth at a near yield potential level. LAI simulation with the proposed model had average RMSE of 0.52 m 2 m -2 for independent data at the two locations. The proposed model has minimum input requirements. Interactions between leaf growth and source-driven processes can be incorporated in the future, while maintaining the basic physiological assumptions underlining leaf expansion and senescence.