• Authors:
    • Torres,C. M.
    • Anton,A.
    • Castells,F.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector (LCA Food 2014)
  • Year: 2014
  • Summary: Certain complexities in the agricultural production differentiate this sector from the conventional industrial processes. The main feature to take into account is that the resources consumption and production is subjected to high variability in soil, rainfall and latitude. We show here an environmental tool developed in close cooperation with farmers in order to achieve applicability and comprehensibility. The procedure relies on the data retrieved from parcel management monitoring of different crops, mostly allocated in Catalonia and Ebro river watershed region (NE Spain). A set of comprehensive but also simple reports are provided, including material and energy balances, agronomic efficiencies and water and carbon footprints. The calculations also cover impacts due to infrastructure, including the estimation of materials in the use of greenhouses. Besides, a simple algorithm for reporting uncertainty using an approximation method of error propagation was added using the input uncertainties as defined by their data pedigree.
  • Authors:
    • Bathke, D. J
    • Oglesby, R. J.
    • Rowe, C. M.
    • Wilhite, D. A.
  • Year: 2014
  • Summary: The goal of this report is to inform policy makers, natural resource managers, and the public about the state of the science on climate change, current projections for ongoing changes over the twenty-first century, current and potential future impacts, and the management and policy implications of these changes. Hopefully, this report will lead to a higher degree of awareness and the initiation of timely and appropriate strategic actions that will enable Nebraskans to prepare for and adapt to future changes to our climate.
  • Authors:
    • Zwickel, T.
    • Van Vuuren, D. P.
    • Winkler, H.
    • Riahi, K.
    • O'Neill, B. C.
    • Mathur, R.
    • Kriegler, E.
    • Edmonds, J.
    • Carter, T. R.
    • Arnell, N. W.
    • Kram, T.
    • Hallegatte, S.
    • Ebi, K. L.
  • Source: Research Article
  • Volume: 122
  • Issue: 3
  • Year: 2014
  • Summary: The scientific community is developing new global, regional, and sectoral scenarios to facilitate interdisciplinary research and assessment to explore the range of possible future climates and related physical changes that could pose risks to human and natural systems; how these changes could interact with social, economic, and environmental development pathways; the degree to which mitigation and adaptation policies can avoid and reduce risks; the costs and benefits of various policy mixes; and the relationship of future climate change adaptation and mitigation policy responses with sustainable development. This paper provides the background to and process of developing the conceptual framework for these scenarios, as described in the three subsequent papers in this Special Issue (Van Vuuren et al., 2013; O'Neill et al., 2013; Kriegler et al., Submitted for publication in this special issue). The paper also discusses research needs to further develop, apply, and revise this framework in an iterative and open-ended process. A key goal of the framework design and its future development is to facilitate the collaboration of climate change researchers from a broad range of perspectives and disciplines to develop policy- and decision-relevant scenarios and explore the challenges and opportunities human and natural systems could face with additional climate change.
  • Authors:
    • Attavanich,Witsanu
    • McCarl,Bruce A.
  • Source: Climatic Change
  • Volume: 124
  • Issue: 4
  • Year: 2014
  • Summary: This paper analyzes the impact of climate, crop production technology, and atmospheric carbon dioxide (CO2) on current and future crop yields. The analysis of crop yields endeavors to advance the literature by estimating the effect of atmospheric CO2 on observed crop yields. This is done using an econometric model estimated over pooled historical data for 1950-2009 and data from the free air CO2 enrichment experiments. The main econometric findings are: 1) Yields of C3 crops (soybeans, cotton, and wheat) directly respond to the elevated CO2, while yields of C4 crops (corn and sorghum) do not, but they are found to indirectly benefit from elevated CO2 in times and places of drought stress; 2) The effect of technological progress on mean yields is non-linear; 3) Ignoring atmospheric CO2 in an econometric model of crop yield likely leads to overestimates of the pure effects of technological progress on crop yields of about 51, 15, 17, 9, and 1 % of observed yield gain for cotton, soybeans, wheat, corn and sorghum, respectively; 4) Average climate conditions and climate variability contribute in a statistically significant way to average crop yields and their variability; and 5) The effect of CO2 fertilization generally outweighs the effect of climate change on mean crop yields in many regions resulting in an increase of 7-22, 4-47, 5-26, 65-96, and 3-35 % for yields of corn, sorghum, soybeans, cotton, and wheat, respectively.
  • Authors:
    • Thompson, A.
    • Chadwick, O. A.
    • Kramer, M. G.
    • Buettner, S. W.
  • Source: Journal
  • Volume: 221
  • Year: 2014
  • Summary: The transport of organic carbon (C) to deep mineral horizons in soils can lead to long-term C stabilization. In basaltic soils, C associations with short-range-ordered (SRO) minerals often lead to colloid-sized aggregates that can be dispersed and mobilized by changes in soil solution chemistry. In the montane forest region of Hawaii, basaltic soils are exposed to high rainfall and anoxic conditions that facilitate ferric (Fe-III) (oxyhydr)oxide reduction. We explored the potential of iron (Fe)-reducing conditions to mobilize C by exposing the surface mineral horizons of three soils from the Island of Hawai'i (aged 03, 20, and 350 ky) to 21 days of anoxic incubation in 1:10 soil slurries. Mobilized C was quantified by fractionating the slurries into three particle-size classes (<430 nm,<60 nm,<23 nm approximate to 10 kDa). In all three soils, we found Fe reduction (maximum Fe2+ (aq) concentration approximate to 17.7 +/- 1.9 mmol kg(-1) soil) resulted in similar to 500% and similar to 700% increase of C in the 23-430 nm, and <23 nm size fractions, respectively. In addition, Fe reduction increased solution ionic strength by 127 mu S cm(-1) and generated hydroxyl ions sufficient to increase the slurry pH by one unit. We compared this to C mobilized from the slurries during a 2-h oxic incubation across a similar range of pH and ionic strength and found smaller amounts of dissolved (<23 nm) and colloidal (23-430 nm) C were mobilized relative to the Fe reduction treatments (p < 0.05). In particular, C associated with the largest particles (60-430 nm) was dispersed almost exclusively during the Fe reduction experiments, suggesting that it had been bound to Feoxide phases. Our experiments suggest that colloidal dispersion during Fe-reducing conditions mobilizes high concentrations of C, which may explain how C migrates to deep mineral horizons in redox dynamic soils. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Gisladottir, G.
    • Zinn, Y. L.
    • Mayes, M. A.
    • Jagadamma, S.
    • Russell, A. E.
  • Source: Article
  • Volume: 213
  • Year: 2014
  • Summary: Dissolved organic carbon (DOC) transported from the soil surface is stabilized in deeper soil profiles by physicochemical sorption processes. However, it is unclear how different forms of organic carbon (OC) compounds common in soil organic matter interact with soil minerals in the surface (A) and subsurface (B) horizons. We added four compounds (glucose, starch, cinnamic acid and stearic acid) to the silt- and clay-sized fraction (fine fraction) of A and B horizons of eight soils from varying climates (3 temperate, 3 tropical, 1 arctic and 1 sub-arctic). Equilibrium batch experiments were conducted using 0 to 100 mg C L-1 of C-14-labeled compounds for 8 h. Sorption parameters (maximum sorption capacity, Q(max) and binding coefficient, k) calculated by fitting sorption data to the Langmuir equation showed that Q(max) of A and B horizons was very similar for all compounds. Both Q(max) and k values were related to sorbate properties, with Q(max) being lowest for glucose (20-500 mg kg(-1)), highest for stearic acid (20,000-200,000 mg kg(-1)), and intermediate for both cinnamic acid (200-4000 mg kg(-1)) and starch (400-6000 mg kg(-1)). Simple linear regression analysis revealed that physicochemical properties of the sorbents influenced the Q(max), of cinnamic acid and stearic acid, but not glucose and starch. The sorbent properties did not show predictive ability for binding coefficient k. By using the fine fraction as sorbent, we found that the mineral fractions of A horizons are equally reactive as the B horizons irrespective of soil organic carbon content. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Hammer, G..
    • Rejesus, R.
    • Little, B.
    • Braun, N.
    • Schlenker, W.
    • Roberts, M.
    • Lobell, D.
  • Source: Science
  • Volume: 344
  • Issue: 6183
  • Year: 2014
  • Summary: A key question for climate change adaptation is whether existing cropping systems can become less sensitive to climate variations. We use a field-level data set on maize and soybean yields in the central United States for 1995 through 2012 to examine changes in drought sensitivity. Although yields have increased in absolute value under all levels of stress for both crops, the sensitivity of maize yields to drought stress associated with high vapor pressure deficits has increased. The greater sensitivity has occurred despite cultivar improvements and increased carbon dioxide and reflects the agronomic trend toward higher sowing densities. The results suggest that agronomic changes tend to translate improved drought tolerance of plants to higher average yields but not to decreasing drought sensitivity of yields at the field scale.
  • Authors:
    • Long, S. P.
    • Ort, D. R.
  • Source: Article
  • Volume: 344
  • Issue: 6183
  • Year: 2014
  • Summary: In total global production, corn (maize, <I>Zea mays</I> L.) is the most important food and feed crop. Of the 967 million metric tons produced in 2013, 36.5% were produced in the United States, mostly in the Midwest Corn Belt. The United States is by far the world's largest corn exporter, accounting for 50% of corn exports globally (<I>1</I>, <I>2</I>). Until recently, breeding and management have allowed farmers to increase the number of plants per acre without loss of yield per plant. On page 516 of this issue, Lobell <I>et al.</I> (<I>3</I>) use a detailed data set for farms across the Corn Belt, to show that increasing yields have been accompanied by rising drought sensitivity, with important implications for future crop yields.
  • Authors:
    • Abella, S. R.
    • Engel, E. C.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Fire is a major process in many ecosystems. Knowledge of fire effects on soils is fundamental to making informed land management decisions to meet objectives such as ecological restoration and promoting C sequestration. We assessed 30, 0 to 5 cm soil properties in interspaces (between shrubs) on 32 wildfires, each paired with their own unburned area and ranging in time since fire (TSF) from 2 to 29 yr, in the Mojave Desert. We analyzed relationships of soil properties to burn status (burned or unburned), TSF, and plant community type (blackbrush, Coleogyne ramosissima Torr., and creosote bush, Larrea tridentata [Sessé & Moc. ex DC] Coville, representing predominant Mojave Desert communities). Organic C and total N were two key properties significantly related to fire, being 25 and 44% greater in burned than unburned areas. Few soil properties exhibited a burn x TSF interaction, indicating that fire presence/absence alone was important. Coleogyne communities displayed greater overall difference between burned and unburned soils than did Larrea communities. Results suggest that: (i) burned areas had significantly greater soil C and total N than unburned areas across communities on this desert landscape, (ii) burned and unburned soils overall were more different in Coleogyne than in Larrea communities, and (iii) TSF was not strongly related to soil properties. © Soil Science Society of America, All rights reserved.
  • Authors:
    • Van Santen, E.
    • Arriaga, F. J.
    • Balkcom, K. S.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Tillage systems that promote minimal surface disturbance combined with high residue cover crops can sequester C, but additional research to quantify carbon sequestration with conservation agricultural systems is needed for modelers, policymakers, and landowners. A factorial arrangement of conservation tillage (no-till, fall paratill, spring paratill, and spring strip-till) and winter cover crops (no cover, rye [Secale cereale L], and wheat [Triticum aestivum L.]) were established in a corn/cotton (Zea mays L./Gossypium hirsutum L.) rotation from 2004 to 2009 to (i) evaluate cover crop biomass production and associated changes in soil organic carbon (SOC) to 15 cm, (ii) evaluate the potential of conservation systems to sequester SOC after years of conventional tillage, and (iii) compare measured changes in SOC to predicted soil conditioning index (SCI) values. Carbon returned to the soil each year averaged 2500 and 1340 kg C ha-1 for cover crops and corn residue, respectively. The average SOC sequestration rate in the top 15 cm was 926 ± 344 kg C ha-1 yr-1. Soil organic C values measured after 6 yr related well with predicted SCI values (r2 = 0.81; P = 0.0004). However, discrepancies between SCI and SOC values for conservation systems highlighted the need to improve the SCI for the Southeast U.S. Conservation systems following years of conventional monocropping were equivalent in their ability to sequester considerable amounts of C that will improve soil quality in the Coastal Plain of the southeastern USA. © Soil Science Society of America, All rights reserved.