• Authors:
    • Montagne, C.
    • Lenssen, A. W.
    • Sainju, U. M.
    • Barsotti, J. L.
    • Hatfield, P. G.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Sheep (Ovis aries L.) grazing is an inexpensive method of weed control in dryland cropping systems, but little is known about its effect on net greenhouse gas (GHG) emissions. We evaluated the effect of sheep grazing compared with herbicide application for weed control on GHG (CO2, N2O, and CH4) emissions from May to October 2010 and 2011, net global warming potential (GWP), and greenhouse gas intensity (GHGI) in a silt loam under dryland cropping systems in western Montana. Treatments were two fallow management practices (sheep grazing [GRAZ] and herbicide application [CHEM]) and three cropping sequences (continuous alfalfa [Medicago sativa L.] [CA], continuous spring wheat [Triticum aestivum L.] [CSW], and spring wheat-pea [Pisum sativum L.]/barley [Hordeum vulgaris L.] hay-fallow [W-P/B-F]). Gas fluxes were measured at 3- to 14-d intervals with a vented, static chamber. Regardless of treatments, GHG fluxes peaked immediately following substantial precipitation (>12 mm) and N fertilization mostly from May to August. Total CO2 flux from May to October was greater under GRAZ with CA, but total N2O flux was greater under CHEM and GRAZ with CSW than other treatments. Total CH4 flux was greater with CA than W-P/B-F. Net GWP and GHGI were greater under GRAZ with W-P/B-F than most other treatments. Greater CH4 flux due to increased enteric fermentation as a result of longer duration of grazing during fallow, followed by reduced crop residue returned to the soil and/or C sequestration rate probably increased net GHG flux under GRAZ with W-P/B-F. Sheep grazing on a cropping sequence containing fallow may not reduce net GHG emissions compared with herbicide application for weed control on continuous crops.
  • Authors:
    • Tatarko, J.
    • Schlegel, A. J.
    • Holman, J. D.
    • Blanco-Canqui, H.
    • Shaver, T. M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Replacement of fallow in crop-fallow systems with cover crops (CCs) may improve soil properties. We assessed whether replacing fallow in no-till winter wheat (Triticum aestivum L.)-fallow with winter and spring CCs for 5 yr reduced wind and water erosion, increased soil organic carbon (SOC), and improved soil physical properties on a Ulysses silt loam (fine-silty, mixed, superactive, mesic Aridic Haplustolls) in the semiarid central Great Plains. Winter triticale (×Triticosecale Wittm.), winter lentil (Lens culinaris Medik.), spring lentil, spring pea (Pisum sativum L. ssp.), and spring triticale CCs were compared with wheat-fallow and continuous wheat under no-till management. We also studied the effect of triticale haying on soil properties. Results indicate that spring triticale and spring lentil increased soil aggregate size distribution, while spring lentil reduced the wind erodible fraction by 1.6 times, indicating that CCs reduced the soil's susceptibility to wind erosion. Cover crops also increased wet aggregate stability and reduced runoff loss of sediment, total P, and NO3-N. After 5 yr, winter and spring triticale increased SOC pool by 2.8 Mg ha-1 and spring lentil increased SOC pool by 2.4 Mg ha-1 in the 0- to 7.5-cm depth compared with fallow. Triticale haying compared with no haying for 5 yr did not affect soil properties. Nine months after termination, CCs had, however, no effects on soil properties, suggesting that CC benefits are short lived in this climate. Overall, CCs, grown in each fallow phase in no-till, can reduce soil erosion and improve soil aggregation in this semiarid climate. © Soil Science Society of America.
  • Authors:
    • Halvorson, A. D.
    • Jantalia, C. P.
    • Follett, R. F.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Conventional tillage (CT) with high N rates and irrigation is used more frequently than no-till (NT) for growing continuous corn (Zea mays L.) in the central Great Plains of the United States. The objective of this study was to evaluate soil organic C (SOC) stocks throughout the soil profile as well as the potential for maintaining or sequestering SOC within the soil profile (0- 120 cm) under irrigated, continuous corn as affected by NT and CT and three N rates. Isotopic δ13C techniques provided information about the fate of C added to soil by corn (C4-C) and of residual C3-C from cool-season plants grown before this study. Relative contributions of C4-C and C3-C to SOC stocks after 8 yr were determined. Retention of C4-C from corn was measured under NT and CT. Nitrogen fertilization slowed losses of C3-C and improved retention of C 4-C. No-till was superior to CT in maintaining SOC. Deep soil sampling to 120 cm and the use of stable C isotope techniques allowed evaluation of changes in SOC stocks during the 8-yr period. Change in SOC under NT vs. CT resulted from greater loss of C3-C stocks under CT throughout the soil profile. Irrigated corn has a low potential to sequester SOC in the central Great Plains, especially under CT. The results of this study indicate that stability of the soil organic matter and its perceived "recalcitrance" is altered by environmental and biological controls. © Soil Science Society of America.
  • Authors:
    • Zobeck, T. M.
    • Moore-Kucera, J.
    • Fultz, L. M.
    • Acosta-Martfnez, V.
    • Allen, V. G.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Integrated crop-livestock (ICL) systems that utilize perennial or high-residue no-till annual forages may build soil organic matter and, thus, enhance aggregate stability, water retention, nutrient cycling, and C storage. We examined long-term effects of ICL management on soil organic C (SOC) pools compared with continuous cotton [CTN; (Gossypium hirsutum L.)] at the system and individual vegetation levels, both using limited irrigation (65 and 77% replacement of évapotranspiration, respectively). Soil samples collected in 1997 (baseline) and 2010 were fractionated into four water stable aggregate-size classes: macroaggregate (>250 μn), microaggregate (53-250 urn), and silt + clay (250 urn), microaggregates (53-250 urn), and silt + clay (<53 urn). Reduced tillage and increased vegetation inputs under WW-B. Dahl Old World bluestem [Bothriochloa bladhii (Retz) S.T. Blake; bluestem], a component of the ICL, resulted in increased mean weight diameter (1.5 mm in bluestem vs. 0.40 mm in CTN) and higher proportions of macroaggregates (59%) than under CTN. A continued increase in SOC was measured in the ICL following 13 yr with 22% more SOC relative to CTN. The results from the detailed soil aggregate C fractionation revealed that an ICL under limited irrigation enhanced SOC stored in protected, recalcitrant aggregate pools (intra-aggregate microaggregate SOC of 8.2 and 5.4 mg g-1 macroaggregate in the ICL and CTN, respectively). These benefits impart important ecosystem services such as potential C sequestration and reduced erosion potential, which are especially important in these semiarid soils. © Soil Science Society of America, All rights reserved.
  • Authors:
    • Young, F. L.
    • Samuel, M. K.
    • Fortuna, A. M.
    • Gollany, H. T.
    • Pan, W. L.
    • Pecharko, M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 2
  • Year: 2013
  • Summary: Accurate estimates of soil organic C (SOC) stocks are required to determine changes in SOC resulting from agricultural management practices. Our objectives were to: (i) determine total SOC; (ii) estimate the contribution of light fraction C (LF-C) to total SOC; and (iii) simulate SOC dynamics using CQESTR to examine the effect of climate change for three cropping systems in the Pacific Northwest. The LF-C masked small gains or losses in measured SOC for all cropping systems. Simulated data indicated no significant changes in SOC in the top 30 cm of the sweep-tillage winter wheat (Triticum aestivum L.)-tillage fallow rotation (WW-TF) and no-till (NT) spring wheat-chemical fallow rotation (SW-CF/NT), whereas SOC increased in the NT spring barley (Hordeum vulgare L.)-spring wheat rotation (SB-SW/NT). The apparent increase in measured SOC with continuous NT spring cropping was the result of accumulated undecomposed crop residues that contributed to the labile C pool and was confirmed via LF-C analysis. The contributions of the LF-C to total SOC across cropping systems ranged from 13.4 to 18.4% (fall soil samples) and 14.4 to 18.9% (spring soil samples). Modeling predicted no significant change in SOC stocks for the WW-TF and SW-CF/NT rotations, even with a 30% crop biomass increase based on potential climate change scenarios. Differences between the observed and predicted SOC were due to artifacts associated with protocols used to determine SOC that did not completely remove accrued crop residue and could be explained by LF-C, which provided a first approximation of organic C accretion. Copyright © 2013 by the Soil Science Society of America, Inc.
  • Authors:
    • Dick, W.
    • Lal, R.
    • Kadono, A.
    • Kumar, S.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 2
  • Year: 2013
  • Authors:
    • Evanylo, G. K.
    • Li, J.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Application of organic amendments (e.g., biosolids[BS], composts) to soil may provide an effective method for accumulating considerable amounts of C, but the long term stability of such C is not well known. We investigated study sites in Virginia to determine the amounts of C remaining in soils 7 to 27 yr following amending with biosolids and composts. The first study employed a Fauquier silty clay loam (fine, mixed, active, mesic Ultic Hapludalf) to which four treatments (control, poultry litter-yard waste compost, biosolids compost, and poultry litter) were continuously applied during 2000-2004. The second study was conducted on a Davidson clay loam (fine, kaolinitic, thermic, Rhodic Kandiudult) to which six rates of aerobically digested biosolids (0, 42, 84, 126, 168, and 210 Mg ha-1) were applied in 1984. The third study was on a Pamunkey sandy loam (fine-loamy, mixed, semiactive, thermic Ultic Hapludalfs) to which five rates of anaerobically digested biosolids (0, 14, 42, 70, and 98 Mg ha-1), with and without sawdust, were applied in 1996. Total soil organic C concentration and bulk density were measured to calculate C accumulation. The organic amendment-treated soils increased C in the surface soil depth (<15 cm), ranging from 2 to 12% of C across all three sites. Soil C movement was limited to a depth of 15 cm. Evidence of C saturation was revealed in the third study site. These results demonstrate that organic amendments applied over a long time remain in soil and may contribute to C sequestration in the Mid-Atlantic region. © Soil Science Society of America.
  • Authors:
    • Mishra, U.
    • Swanston, C. W.
    • Nave, L. E.
    • Nadelhoffer, K. J.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Afforestation (tree establishment on nonforested land) is a management option for increasing terrestrial C sequestration and mitigating rising atmospheric carbon dioxide because, compared to nonforested land uses, afforestation increases C storage in aboveground pools. However, because terrestrial ecosystems typically store most of their C in soils, afforestation impacts on soil organic carbon (SOC) storage are critical components of ecosystem C budgets. We applied synthesis methods to identify the magnitude and drivers of afforestation impacts on SOC, and the temporal and vertical distributions of SOC change during afforestation in the United States. Meta-analysis of 39 papers from 1957 to 2010 indicated that previous land use drives afforestation impacts on SOC in mineral soils (overall average = +21%), but mined and other industrial lands (+173%) and wildlands (+31%) were the only groups that specifically showed categorically significant increases. Temporal patterns of SOC increase were statistically significant on former industrial and agricultural lands (assessed by continuous metaanalysis), and suggested that meaningful SOC increases require ≥15 and 30 yr of afforestation, respectively. Meta-analysis of 13C data demonstrated the greatest SOC changes occur at the surface soil of the profile, although partial replacement of C stocks derived from previous land uses was frequently detectable below 1 m. A geospatial analysis of 409 profiles from the National Soil Carbon Network database supported 13C meta-analysis results, indicating that transition from cultivation to forest increased A horizon SOC by 32%. In sum, our findings demonstrate that afforestation has significant, positive effects on SOC sequestration in the United States, although these effects require decades to manifest and primarily occur in the uppermost (and perhaps most vulnerable) portion of the mineral soil profile.
  • Authors:
    • Olson, K. R.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 2
  • Year: 2013
  • Authors:
    • Sequeira, C.
    • Chiaretti, J.
    • Seybold, C.
    • Wills, S.
    • West, L.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Previous assessments of soil organic carbon (SOC) stocks have used soil maps and other tacit knowledge from soil survey to aggregate and extrapolate data without assessing the relationship between SOC and the tacit information used. The objective of this paper is to outline a process that translates tacit class-based knowledge into semiquantitative information about SOC stocks. This information was used to create a soil-based strata for sample selection to inventory SOC stocks. The process was completed in three steps: (i) official series descriptions (OSDs) were used to compile comprehensive soil information, (ii) an ordinal scoring system was developed and applied to link soil properties to likely SOC stocks, and (iii) hierarchical clustering was applied to cluster soils into groups for sampling. The scores and groups were tested using pedon SOC stocks from the National Cooperative Soil Survey laboratory database. Expert soil scientists interpreted individual terms used in Soil Taxonomy and OSDs for their explicit or implicit relationships with SOC stocks. Taxa, soil moisture regime, and temperature regime were separated as individual factors. Other information from the OSDs including family particle size class, depth to restrictive layer, and drainage class were used to translate qualitative information into ordinal scores. Classes for taxonomic order, soil moisture regimes, and drainage class were significantly different in pedon SOC stocks across and within regions. Scores within each factor (taxonomy, moisture regime, drainage class, temperature regime, and soil depth) were also significantly different from one another in pedon SOC stocks. Ordinal scores were used to cluster soils within each of 17 regions. Soil groups were significantly different from one another in SOC stocks in each of the 17 sampling regions. The process was considered satisfactory and was used to stratify soils for SOC stock sampling in the conterminous United States. A similar process could be applied to any soil property over any area of interest to evaluate tacit knowledge for communicating soil information, grouping soils for interpretation, or creating strata for distributing samples.