• Authors:
    • Albrecht, S. L.
    • Douglas, C. L., Jr.
    • Reardon, C. L.
    • McCool, D. K.
    • Williams, J. D.
    • Rickman, R. W.
  • Source: Journal of Soil and Water Conservation
  • Volume: 68
  • Issue: 5
  • Year: 2013
  • Summary: Roots, cereal crowns, and stems growing beneath the soil surface provide important resistance to soil erosion. Understanding the amount and distribution of this material in the soil profile could provide insight into resistance to soil erosion by water and improve the performance of soil erosion models, such as the revised universal soil loss equation (RUSLE) and the water erosion prediction project (WEPP). Erosion models use built-in or external crop growth models to populate crop yield and live aboveground and associated belowground biomass databases. We examined two data sets from the dryland small grain production region in the Pacific Northwest of the United States to determine root:shoot ratios, the vertical distribution of root and attached belowground biomass, and incorporated residue from previously grown crops. Data were collected in 1993, 1994, 1995, and 2000 from short-term no-till and conventional tillage experiments conducted near Pendleton, Oregon, and Pullman,Washington, and in 1999 and 2000 from long-term experiments representative of farming practices near Pendleton, Oregon. The crops sampled in the short-term data set included soft white winter and spring wheat (Triticum aestivum L.;WW and SW, respectively), spring peas (Pisum sativum L.; SP), and winter canola (Brassica napus L.;WC). Crops sampled in the long-term study included WW SW, and SP. Data were collected at harvest in both data sets and during three phenologic stages in each of the crops in the short-term data set. Soil samples were collected to a depth of 60 cm (23.6 in) in the short-term and 30 cm (11.9 in) in the long-term experiments. In both sets of measurements, we found greater than 70% of root mass is in the top 10 cm (3.9 in) of the soil profile with the exception of SP, which had 70% of root mass in the top 15 cm (5.9 in) of the soil profile.WC produced significantly more biomass near the soil surface than WW SW, or SP Root-to-shoot biomass ratios, in mature wheat ranged from 0.13 to 0.17 in the top 30 cm (11.9 in) of the soil profile, substantially lower than values suggested for use in WEPP (0.25). In the long-term experiments, soil of the conventionally tilled continuous winter wheat (CWW) plots contained significantly greater biomass than soil of conventionally tilled winter wheat/fallow (CR) and no-till winter wheat/fallow (NT) treatments. There was no significant difference between CWW and conventionally tilled winter wheat/spring pea (WP); however, CWW returned more residue to the soil than WP because SP produced less residue and these residues were incorporated with a field cultivator rather than a moldboard plow. More accurate representation of root development, particularly in winter crops, could improve RUSLE and WEPP performance in the Pacific Northwest where winter conditions have proven difficult to model.
  • Authors:
    • Ingram, D. L.
  • Source: JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE
  • Volume: 138
  • Issue: 1
  • Year: 2013
  • Summary: The contributions of interrelated production system components of a field-grown, 2-m-tall, 5-cm-caliper Picea pungens (colorado blue spruce) in the upper midwestern (liner) and lower midwestern (finished tree) regions of the United States to its carbon footprint were analyzed using life cycle assessment protocols. The seed-to-landscape carbon footprint was 13.558 kg carbon dioxide equivalent (CO(2)e), including sequestration of 9.14 kg CO(2)e during production. The global warming potential (GWP) from equipment use was the dominant contributor to the carbon footprint of production. Seventy-six percent of the GWP investments during field production occurred at harvest. Querying the model, among other things, revealed that adding one year to the field production phase would add less than 3% to the seed-to-landscape GWP of the product. The weighted positive impact of carbon (C) sequestration during a 50-year life was 593 kg CO(2)e. After its useful life, takedown and disposal would result in emissions of 148 kg CO(2)e, resulting in a net positive, life cycle impact on atmospheric CO2 of approximate to 431 kg CO(2)e.
  • Authors:
    • Suddick, E. C.
    • Kennedy, T. L.
    • Six, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 170
  • Issue: April
  • Year: 2013
  • Summary: Understanding the effect of various agricultural management practices on nitrous oxide (N2O) emissions is crucial to advise farmers and formulate policies for future greenhouse gas (GHG) reductions. In order to estimate present N2O emissions, annual N2O budgets must be thoroughly and precisely quantified from current farms under conventional and alternative management, but subject to practical and economic constraints. In this study, field sites were located on two on-farm processing tomato (Lycopersicon esculentum) fields, under contrasting irrigation managements and their associated fertilizer application strategy: (1) furrow irrigation and sidedress fertilizer injection (conventional system) and (2) drip irrigation, reduced tillage, and fertigation (integrated system). Nitrous oxide emissions were monitored for seven to ten days following major events of cultivation, irrigation, fertilization, harvest, and winter precipitations. Total weighted growing season emissions (15 March-1 November 2010) were 2.01 +/- 0.19 kg N2O-N ha(-1) and 0.58 +/- 0.06 kg N2O-N ha(-1) in the conventional and integrated systems, respectively. The highest conventional system N2O emission episodes resulted from fertilization plus irrigation events and the first fall precipitation. In the integrated system, the highest N2O fluxes occurred following harvest and the first fall precipitation. Soil chemical and physical properties of soil moisture, inorganic nitrogen (N), and dissolved organic carbon (DOC) were low and less spatially variable in the integrated system. Used as an index of substrate availability, soil ammonium (NH4+) and nitrate (NO3-) exposures were significantly lower in the integrated system. Of great importance is that the drip irrigation water and fertilizer management of the integrated system also increased crop yield (119 Mg ha(-1) vs. 78 Mg ha(-1)), highlighting the potential for decreasing N2O emissions while simultaneously improving the use of water and fertilizer for plant production. Published by Elsevier B.V.
  • Authors:
    • Giltrap, D.
    • Hernandez-Ramirez, G.
    • Kim, D.-G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 168
  • Issue: March
  • Year: 2013
  • Summary: Rising atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and associated climate change. It is often assumed that there is a linear relationship between nitrogen (N) input and direct N2O emission in managed ecosystems and, therefore, direct N2O emission for national greenhouse gas inventories use constant emission factors (EF). However, a growing body of studies shows that increases in direct N2O emission are related by a nonlinear relationship to increasing N input. We examined the dependency of direct N2O emission on N input using 26 published datasets where at least four different levels of N input had been applied. In 18 of these datasets the relationship of direct N2O emission to N input was nonlinear (exponential or hyperbolic) while the relationship was linear in four datasets. We also found that direct N2O EF remains constant or increases or decreases nonlinearly with changing N input. Studies show that direct N2O emissions increase abruptly at N input rates above plant uptake capacity. The remaining surplus N could serve as source of additional N2O production, and also indirectly promote N2O production by inhibiting biochemical N2O reduction. Accordingly, we propose a hypothetical relationship to conceptually describe in three steps the response of direct N2O emissions to increasing N input rates: (1) linear (N limited soil condition), (2) exponential, and (3) steady-state (carbon (C) limited soil condition). In this study, due to the limited availability of data, it was not possible to assess these hypothetical explanations fully. We recommend further comprehensive experimental examination and simulation using process-based models be conducted to address the issues reported in this review. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Franzluebbers, A. J.
    • Andrews, S. S.
    • Kome, C. E.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 68
  • Issue: 4
  • Year: 2013
  • Summary: Simple, yet reliable models are needed to quantify soil organic carbon (SOC) changes for the wide diversity of agricultural management conditions in the United States. We compared the outputs of two relatively simple models currently available for farmers and government-financed farm support agencies: the Carbon (C) Management Evaluation Tool for Voluntary Reporting of Greenhouse Gases (COMET-VR) and the Soil Conditioning Index (SCI). Simulations were conducted for 18 locations throughout the United States for five soil textural regimes (loamy sand, sandy loam, silt loam, clay loam, and silty clay loam), three tillage management systems (conventional tillage [CT], minimum tillage [MT], and no tillage [NT]), and two crop rotations (wheat [Triticum aestivum L.]-potato [Solanum tuberosum L.] and wheat-four-year alfalfa [Medicago sativa L.] in western states and corn [Zea mays L.]-soybean [Glycine max L.] and corn-soybean-wheat in eastern states). Both models ranked SOC change as NT > MT > CT, whereby SOC change decreased with increasing soil disturbance with tillage However, models were divergent with regards to soil texture; SOC change was greater in coarse-textured than in fine-textured soils with COMET-VR, but SOC change was lower in coarse-textured than in fine-textured soils with SCI. For crop rotations, SOC change was greater or equal in simpler than in more complex rotation with COMET-VR, but smaller in simpler than in more complex rotations with SCI. Overall, SOC sequestration predicted by COMET-VR was positively related to SCI score, especially when accounting for differences in environmental conditions of a location. Our results suggest that both Models have value and limitations and that measures of SOC sequestration are predictable with these tools under a diversity of typical management conditions in the United States.
  • Authors:
    • Wander, M. M.
    • Dunn, J. B.
    • Mueller, S.
    • Kwon, H.-Y.
  • Source: Biomass and Bioenergy
  • Volume: 55
  • Issue: August
  • Year: 2013
  • Summary: Current estimates of life cycle greenhouse gas emissions of biofuels produced in the US can be improved by refining soil C emission factors (EF; C emissions per land area per year) for direct land use change associated with different biofuel feedstock scenarios. We developed a modeling framework to estimate these EFs at the state-level by utilizing remote sensing data, national statistics databases, and a surrogate model for CENTURY's soil organic C dynamics submodel (SCSOC). We estimated the forward change in soil C concentration within the 0-30 cm depth and computed the associated EFs for the 2011 to 2040 period for croplands, grasslands or pasture/hay, croplands/conservation reserve, and forests that were suited to produce any of four possible biofuel feedstock systems [corn (Zea Mays L)-corn, corn-corn with stover harvest, switchgrass (Panicum virgatum L), and miscanthus (Miscanthus x giganteus Greef et Deuter)]. Our results predict smaller losses or even modest gains in sequestration for corn based systems, particularly on existing croplands, than previous efforts and support assertions that production of perennial grasses will lead to negative emissions in most situations and that conversion of forest or established grasslands to biofuel production would likely produce net emissions. The proposed framework and use of the SCSOC provide transparency and relative simplicity that permit users to easily modify model inputs to inform biofuel feedstock production targets set forth by policy. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Lal, R.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 28
  • Issue: 2
  • Year: 2013
  • Summary: Ecosystem functions and services provided by soils depend on land use and management. The objective of this article is to review and synthesize relevant information on the impacts of no-till (NT) management of croplands on ecosystem functions and services. Sustainable management of soil through NT involves: (i) replacing what is removed, (ii) restoring what has been degraded, and (iii) minimizing on-site and off-site effects. Despite its merits, NT is adopted on merely similar to 9% of the 1.5 billion ha of global arable land area. Soil's ecosystem services depend on the natural capital (soil organic matter and clay contents, soil depth and water retention capacity) and its management. Soil management in various agro-ecosystems to enhance food production has some trade-offs/disservices (i. e., decline in biodiversity, accelerated erosion and non-point source pollution), which must be minimized by further developing agricultural complexity to mimic natural ecosystems. However, adoption of NT accentuates many ecosystem services: carbon sequestration, biodiversity, elemental cycling, and resilience to natural and anthropogenic perturbations, all of which can affect food security. Links exist among diverse ecosystem services, such that managing one can adversely impact others. For example, increasing agronomic production can reduce biodiversity and deplete soil organic carbon (SOC), harvesting crop residues for cellulosic ethanol can reduce SOC, etc. Undervaluing ecosystem services can jeopardize finite soil resources and aggravate disservices. Adoption of recommended management practices can be promoted through payments for ecosystem services by a market-based approach so that risks of disservices and negative costs can be reduced either through direct economic incentives or as performance payments.
  • Authors:
    • Osborne, S. L.
    • Lehman, R. M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 170
  • Issue: April
  • Year: 2013
  • Summary: We determined soil surface fluxes of greenhouse gases (carbon dioxide, nitrous oxide, methane) from no-till, dryland corn (Zea mays L.) in eastern South Dakota and tested the effect of rotation on greenhouse gas fluxes from corn. The corn was grown within a randomized, complete block study that included both a 2-year (corn-soybean) rotation and a 4-year (corn-field peas-winter wheat-soybean) rotation with plots containing the corn phase present in every year, 2007-2010. Annual carbon dioxide (CO2) fluxes were between 1500 and 4000 kg CO2-C ha(-1) during the four-year study. Annual nitrous oxide (N2O) fluxes ranged from 0.8 to 1.5 kg N2O-N ha(-1) with peak fluxes during spring thaw and following fertilization. Net methane (CH4) fluxes in 2007 were close to zero, while fluxes for 2008-2010 were between 0.9 and 1.6 kg CH4-C ha(-1). Methane fluxes increased with consistently escalating values of soil moisture over the four-year period demonstrating that soils which previously exhibited neutral or negative CH4 flux may become net CH4 producers in response to multiyear climatic trends. No significant differences in gas fluxes from corn due to treatment (2-year vs. 4-year rotation) were observed. Mean net annual soil surface gas fluxes from corn calculated over four years for both treatments were 2.4 Mg CO2-C ha(-1), 1.2 kg N2O-N ha(-1), and 0.9 kg CH4-C ha(-1). Annual global warming potentials (GWP) as CO2 equivalents were 572 kg ha(-1) and 30 kg ha(-1) for N2O and CH4, respectively. Measurements of soil carbon showed that the 4-yr rotation accrued 596 kg C ha(-1) yr(-1) in the top 30 cm of soil which would be more than sufficient (2.19 Mg CO2 eq ha(-1) yr(-1)) to offset the annual GWP of the nitrous and methane emissions from corn. In contrast, the 2-year rotation lost 120 kg C ha(-1) yr(-1) from the top 30 cm of soil resulting in corn being a net producer of greenhouse gases and associated GWP. Published by Elsevier B.V.
  • Authors:
    • Lenka, N. K.
    • Lal, R.
  • Source: Soil and Tillage Research
  • Volume: 126
  • Year: 2013
  • Summary: Mulching effect on carbon (C) sequestration depends on soil properties, mulch material, and the rate and duration of application. Thus, rate of soil C sequestration was assessed on a 15 year field study involving three levels of wheat straw at 0 (M-o), 8 (M-8) and 16 (M-16) Mg ha(-1) yr(-1), at two levels (244 kg N ha(-1) yr(-1), F-1 and without, F-0) of supplemental N. Soil C concentration was assessed in relation to aggregation and occlusion in aggregates of a silt loam Alfisol under a no-till (NT) and crop-free system in central Ohio. In comparison to control, soil organic carbon (SOC) concentration in the 0-10 cm depth of bulk soil increased by 32% and 90% with M-8 and M-16 treatments with a corresponding increase in the SOC stock by 21-25% and 50-60%, respectively. With increase in rate of residue mulch, proportion of water stable aggregates (small macroaggregates, >250 mu m size) increased by 1.4-1.8 times and of microaggregates (53-250 mu m) by 1.4 times. Fertilizer N significantly increased the SOC concentration of small macroaggregates under M-16 treatments only. Ultra-sonication showed that 12-20% of SOC occluded in the inter-microaggregate space of small macroaggergates, was a function of both mulch and fertilizer rates. Significantly higher and positive correlation of greenhouse gases (GHGs), CO2, CH4 and N2O flux was observed with C and N concentrations of small macroaggregates and also of the occluded fraction of small macroaggregates. The higher correlation coefficient indicated the latter to be prone to microbial attack. On the contrary, non-significant relationship with C and N concentrations of microaggregates indicate a possible protection of microaggregate C. The diurnal fluxes of CO2, CH4 and N2O were the lowest under bare soil and the highest under high mulch rate with added N, with values ranging from 1.51 to 2.31 g m(-2) d(-1), -2.79 to 3.15 mg m(-2) d(-1) and 0.46 to 1.02 mg m(-2) d(-1), respectively. Mulch rate affected the GHGs flux more than did the fertilizer rates. The net global warming potential (GWP) was higher for high mulch (M-16) than low mulch (M-8) rates, with values ranging from 0.46 to 0.57 Mg CO2 equivalent - C ha(-1) yr(-1) (M-8) and 1.98 to 3.05 Mg CO2 equivalent - C ha(-1) yr(-1) (M-16). In general, mulch rate determined the effect of fertilizers. The study indicated that overlong-term, a mulch rate between 8 and 16 Mg ha(-1) yr(-1) may be optimal for Alfisols in Central Ohio. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Shi, W.
    • Bowman, D.
    • Hu, F.
    • Li, X.
  • Source: Applied Soil Ecology
  • Volume: 67
  • Issue: May
  • Year: 2013
  • Summary: Soil N2O emissions can affect global environments because N2O is a potent greenhouse gas and ozone depletion substance. In the context of global warming, there is increasing concern over the emissions of N2O from turfgrass systems. It is possible that management practices could be tailored to reduce emissions, but this would require a better understanding of factors controlling N2O production. In the present study we evaluated the spatial variability of soil N2O production and its correlation with soil physical, chemical and microbial properties. The impacts of grass clipping addition on soil N2O production were also examined. Soil samples were collected from a chronosequence of three golf courses (10, 30, and 100-year-old) and incubated for 60 days at either 60% or 90% water filled-pore space (WFPS) with or without the addition of grass clippings or wheat straw. Both soil N2O flux and soil inorganic N were measured periodically throughout the incubation. For unamended soils, cumulative soil N2O production during the incubation ranged from 75 to 972 ng N g(-1) soil at 60% WFPS and from 76 to 8842 ngN g(-1) soil at 90% WFPS. Among all the soil physical, chemical and microbial properties examined, soil N2O production showed the largest spatial variability with the coefficient of variation similar to 110% and 207% for 60% and 90% WFPS, respectively. At 60% WFPS, soil N2O production was positively correlated with soil clay fraction (Pearson's r= 0.91, P2.5% organic C. Net N mineralization in soil samples with >2.5% organic C was similar between the two moisture regimes, suggesting that O-2 availability was greater than expected from 90% WFPS. Nonetheless, small and moderate changes in the percentage of clay fraction, soil organic matter content, and soil pH were found to be associated with large variations in soil N2O production. Our study suggested that managing soil acidity via liming could substantially control soil N2O production in turfgrass systems. (C) 2013 Elsevier B.V. All rights reserved.