• Authors:
    • Burow, G.
    • Xin, Z. Q.
    • Chen, J. P.
    • Payton, P.
    • Burke, J. J.
    • Hayes, C.
  • Source: Crop Science
  • Volume: 55
  • Issue: 1
  • Year: 2015
  • Summary: Water-deficit stress responses in sorghum [Sorghum bicolor (L.) Moench] have been described in the literature as preflowering drought tolerant (postflowering senescent) or postflowering drought tolerant (preflowering drought sensitive). The underlying physiological mechanisms associated with these drought traits remain unclear. It was hypothesized that the preflowering drought sensitivity of stay-green lines could be related to reported differences in osmotic potential among stay-green and senescent lines resulting in an inability of the cultivars to either sense or respond the soil drying until the rate of drying is too great for the stay-green lines to compensate. The objective of this study was to measure stress-induced changes in relative water content, abscisic acid (ABA), proline, dhurrin, sucrose, and carbon assimilation during the onset of water-deficit stress in the preflowering drought-tolerant line SC1211-11E and the postflowering drought-tolerant line BTx642 to determine if there were differential responses to the onset of soil drying. In both greenhouse and field studies, it was found that SC1211-11E had lower relative water contents and accumulated higher levels of ABA and proline than the BTx642. The SC1211-11E also showed increases in carbon assimilation shortly after the cessation of irrigation that declined with prolonged stress. These results provide new insights into the differential responses of pre and postflowering drought-tolerant sorghum lines.
  • Authors:
    • Li, Z. P.
    • Sohl, T.
    • Sleeter, B.
    • Wein, A.
    • Bliss, N.
    • Ratliff, J.
    • Byrd, K.
  • Source: MITIGATION AND ADAPTATION STRATEGIES FOR GLOBAL CHANGE
  • Volume: 20
  • Issue: 3
  • Year: 2015
  • Summary: We examined opportunities for avoided loss of wetland carbon stocks in the Great Plains of the United States in the context of future agricultural expansion through analysis of land-use land-cover (LULC) change scenarios, baseline carbon datasets and biogeochemical model outputs. A wetland map that classifies wetlands according to carbon pools was created to describe future patterns of carbon loss and potential carbon savings. Wetland avoided loss scenarios, superimposed upon LULC change scenarios, quantified carbon stocks preserved under criteria of carbon densities or land value plus cropland suitability. Up to 3420 km(2) of wetlands may be lost in the region by 2050, mainly due to conversion of herbaceous wetlands in the Temperate Prairies where soil organic carbon (SOC) is highest. SOC loss would be approximately 0.20 +/- 0.15 megagrams of carbon per hectare per year (MgC ha(-1) yr(-1)), depending upon tillage practices on converted wetlands, and total ecosystem carbon loss in woody wetlands would be approximately 0.81 +/- 0.41 MgC ha(-1) yr(-1), based on biogeochemical model results. Among wetlands vulnerable to conversion, wetlands in the Northern Glaciated Plains and Lake Agassiz Plains ecoregions exhibit very high mean SOC and on average, relatively low land values, potentially creating economically competitive opportunities for avoided carbon loss. This mitigation scenarios approach may be adapted by managers using their own preferred criteria to select sites that best meet their objectives. Results can help prioritize field-based assessments, where site-level investigations of carbon stocks, land value, and consideration of local priorities for climate change mitigation programs are needed.
  • Authors:
    • Davies, E.
    • Kyle, P.
    • Clarke, L.
    • Edmonds, J .
    • Hejazi, M.
    • Chaturvedi, V.
    • Wise, M.
  • Source: MITIGATION AND ADAPTATION STRATEGIES FOR GLOBAL CHANGE
  • Volume: 20
  • Issue: 3
  • Year: 2015
  • Summary: Measures to limit greenhouse gas concentrations will result in dramatic changes to energy and land systems and in turn alter the character of human requirements for water. We employ the global change assessment model (GCAM), an integrated assessment model, to explore the interactions of energy, land, and water systems under combinations of three alternative radiative forcing stabilization levels and two carbon tax regimes. The paper analyzes two important research questions: i) how large may global irrigation water demands become over the next century, and ii) what are the potential impacts of emissions mitigation policies on global irrigation-water withdrawals. We find that increasing population and economic growth could more than double the demand for water for agricultural systems in the absence of climate policy, and policies to mitigate climate change further increase agricultural demands for water. The largest increases in agricultural irrigation water demand occur in scenarios where only fossil fuel emissions are priced (but not land use change emissions) and are primarily driven by rapid expansion in bio-energy production. Regions such as China, India, and other countries in South and East Asia are likely to experience the greatest increases in water demands. Finally, we test the sensitivity of water withdrawal demands to the share of bio-energy crops under irrigation and conclude that many regions have insufficient space for heavy bio-energy crop irrigation in the future-a result that calls into question the physical possibility of producing the associated biomass energy, especially under climate policy scenarios.
  • Authors:
    • Filser, J.
    • Vincze, T.
    • Strandberg, B.
    • Cortet, J.
    • Sechi, V.
    • Larsen, T.
    • D'Annibale, A.
    • Audisio, P. A.
    • Krogh, P. H.
  • Source: Soil Biology and Biochemistry
  • Volume: 84
  • Year: 2015
  • Summary: We hypothesized that the combined effect of rising levels of atmospheric carbon dioxide (CO2) and increasing use of genetically modified (GM) crops in agriculture may affect soil food-webs. So we designed a study for the assessment of the effects of elevated CO2 (eCO2) concentrations and GM barley on a soil-mesofauna community employing a 2nd tier mesocosm test system. The GM barley, Hordeum vulgare cv. Golden Promise, had a modified content of amino acids and it was compared with three non-GM barley cultivated varieties including the isogenic line. Our mesocosm experiment was conducted in a greenhouse at ambient (aCO2) and eCO2 (+80ppm) levels and included a multispecies assemblage of Collembola, Acari and Enchytraeidae with either a GM or conventional spring barley varieties. To detect food-web changes we added dried maize leaves naturally enriched in d13C and d15N relative to the soil substrate. Soil, plants and animals were collected after five and eleven weeks. We found that the eCO2 concentration did not affect the plant biomass, but the predatory mite and two collembolan species showed significantly lower abundances at eCO2. The densities of three collembolan species (Folsomia fimetaria, Proisotoma minuta and juveniles of Mesaphorura macrochaeta) was significantly lower in the GM treatment compared to some of the non-GM varieties. F.fimetaria was less abundant in presence of GM barley compared to the cultivated barley variety "Netto" at both CO2 levels, while the density of P.minuta was significantly reduced with the GM barley compared to variety "Netto" at aCO2 and the isogenic variety at eCO2. Maize litter acted as a food source for the community, as it was revealed by d13C values in microarthropods. Microarthropod d13C decreased over time, which indicates a diet change of the species towards carbon derived from barley, due to maize litter decomposition. The industrially produced CO2 gas also had a role as an isotopic marker, as the different d13C values were reflected in the barley and in the collembolan species. GM barley did not affect d13C and d15N values of soil animals indicating that the overall trophic structure of the mesofauna community was not changed compared to the non-GM cultivated varieties. The mesocosm methodology integrating stable isotope analysis demonstrates the potential of the multi-species mesocosm as a tool to detect and track changes in the soil trophic interactions in response to environmental pressures, climate and novel agricultural crops.
  • Authors:
    • Rice, C. W.
    • Suddick, E. C.
    • Davidson, E. A.
    • Prokopy, L. S.
  • Source: JOURNAL OF ENVIRONMENTAL QUALITY
  • Volume: 44
  • Issue: 2
  • Year: 2015
  • Summary: Synthetic nitrogen fertilizer has been a double-edged sword, greatly improving human nutrition during the 20th century but also posing major human health and environmental challenges for the 21st century. In August 2013, about 160 agronomists, scientists, extension agents, crop advisors, economists, social scientists, farmers, representatives of regulatory agencies and nongovernmental organizations (NGOs), and other agricultural experts gathered to discuss the vexing challenge of how to produce more food to nourish a growing population while minimizing pollution to the environment. This collection of 14 papers authored by conference participants provides a much needed analysis of the many technical, economic, and social impediments to improving nitrogen use efficiency (NUE) in crop and animal production systems. These papers demonstrate that the goals of producing more food with low pollution (Mo Fo Lo Po) will not be achieved by technological developments alone but will also require policies that recognize the economic and social factors affecting farmer decision-making. Take-home lessons from this extraordinary interdisciplinary effort include the need (i) to develop partnerships among private and public sectors to demonstrate the most current, economically feasible, best management NUE practices at local and regional scales; (ii) to improve continuing education to private sector retailers and crop advisers; (iii) to tie nutrient management to performance-based indicators on the farm and in the downwind and downstream environment; and (iv) to restore investments in research, education, extension, and human resources that are essential for developing the interdisciplinary knowledge and innovative skills needed to achieve agricultural sustainability goals.
  • Authors:
    • Reicosky, D. C.
    • Panosso, A. R.
    • de Figueiredo, E. B.
    • La Scala, N.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 2
  • Year: 2015
  • Summary: New management strategies should be identified to increase the potential of bioenergy crops to minimize climate change. This study quantified the impact of sugarcane (Saccharum spp.) harvest systems, straw and soil management on carbon dioxide (CO2) fluxes prior to crop replanting carried out on February 2010 in southern Brazil. The soil studied was classified as Haplustult (USDA Soil Taxonomy). Three sugarcane harvest systems were considered: burned (BH) and green harvest with straw maintained on (GH SM) or removed from (GH SR) the soil surface. Our hypothesis is that intensive tillage and the management of sugarcane crop straw could lead to higher CO2 emissions from soil. We measured CO2 emissions in no-till (NT) conditions and after conventional tillage (CT), and with or without dolomite and agricultural gypsum applications. Soil CO2 emissions were measured with a Li Cor chamber (Model Li-8100). Water content of soil and soil temperature readings were first taken 24 h after tillage, over the next 25 days after tillage with 18 measurement days. The removal of sugarcane straw from the soil surface resulted in the rapid reduction of water content of soil (6% in volume) followed by a 64% increase in soil CO2-C emissions, supporting our hypothesis. Additional soil CO2-C emissions caused by removal of crop straw were 253 kg CO2-C ha-1, which is as high as CO2-C losses induced by tillage. Dolomite and agricultural gypsum applications did not always increase CO2 emissions, especially when applied on soil surface with crop straw and tilled. The conversion from burned to green harvest systems can improve the soil C sequestration rate in sugarcane crops when combined with reduced tillage and straw maintenance on soil surface. The effect of straw removal and related CO2 emission for electricity generation should be considered in further studies from sugarcane areas. © 2014 John Wiley & Sons Ltd.
  • Authors:
    • Verger, E. O.
    • Martin, A.
    • Rehm, C. D.
    • Drewnowski, A.
    • Voinnesson, M.
    • Imbert, P.
  • Source: AMERICAN JOURNAL OF CLINICAL NUTRITION
  • Volume: 101
  • Issue: 1
  • Year: 2015
  • Summary: Background: A carbon footprint is the sum of greenhouse gas emissions (GHGEs) associated with food production, processing, transporting, and retailing. Objective: We examined the relation between the energy and nutrient content of foods and associated GHGEs as expressed as g CO 2 equivalents. Design: GHGE values, which were calculated and provided by a French supermarket chain, were merged with the Composition Nutritionnelle des Aliments (French food-composition table) nutrient-composition data for 483 foods and beverages from the French Agency for Food, Environmental and Occupational Health and Safety. Foods were aggregated into 34 food categories and 5 major food groups as follows: meat and meat products, milk and dairy products, frozen and processed fruit and vegetables, grains, and sweets. Energy density was expressed as kcal/100 g. Nutrient density was determined by using 2 alternative nutrient-density scores, each based on the sum of the percentage of daily values for 6 or 15 nutrients, respectively. The energy and nutrient densities of foods were linked to log-transformed GHGE values expressed per 100 g or 100 kcal. Results: Grains and sweets had lowest GHGEs (per 100 g and 100 kcal) but had high energy density and a low nutrient content. The more-nutrient-dense animal products, including meat and dairy, had higher GHGE values per 100 g but much lower values per 100 kcal. In general, a higher nutrient density of foods was associated with higher GHGEs per 100 kcal, although the slopes of fitted lines varied for meat and dairy compared with fats and sweets. Conclusions: Considerations of the environmental impact of foods need to be linked to concerns about nutrient density and health. The point at which the higher carbon footprint of some nutrient-dense foods is offset by their higher nutritional value is a priority area for additional research.
  • Authors:
    • Stoddard, F. L.
    • Simojoki, A.
    • Makela, P.
    • Jaakkola, S.
    • Santanen, A.
    • Saikkonen, L.
    • Epie, K. E.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 2
  • Year: 2015
  • Summary: Bioenergy cropping, like all agricultural practices, may lead to the release of greenhouse gases. This study was aimed at determining biomass and energy yields of reed canary grass (RCG) (Phalaris arundinacea), galega (Galega orientalis) and a mixture of these, and to relate these to fluxes of nitrous oxide (N2O), a potent greenhouse gas, emitted from the soils. Plots including a bare fallow as control were established in 2008. Gases emitted from the soil surface were collected in closed chambers from May 2011 to May 2013, except during periods of snow cover, and analysed by gas chromatography. Seasonal and annual cumulative emissions of N2O and CO2 equivalents per unit energy yield were calculated. Soil moisture content, nitrate (NO3 (-))-N and ammonium (NH4 (+))-N were also determined. Both species composition and crop yields affected energy yields and N2O emission from the soil. The annual cumulative emissions from mixture were marginally lower than those from fertilized RCG soils. Fertilized RCG produced twice as much biomass and correspondingly higher nitrogen and energy yields, so its low emission of N2O per Mg of dry matter was not significantly different from that of the mixtures. Cropping an RCG-galega mixture for biofuel may replace N fertilizer input since it resulted in lowering N2O fluxes, but requires management to maintain grass as the major component in order to minimize N2O emissions. In a time of climate change, low-input bioenergy crops may be a suitable strategy for land left uncropped after ploughing for one season or longer.
  • Authors:
    • Dirocco, T. L.
    • Ramage, B. S.
    • Evans, S. G.
    • Potts, M. D.
  • Source: ENVIRONMENTAL SCIENCE & TECHNOLOGY
  • Volume: 49
  • Issue: 4
  • Year: 2015
  • Summary: Decisions concerning future land-use/land cover change stand at the forefront of ongoing debates on how to best mitigate climate change. In this study, we compare the greenhouse gas (GHG) mitigation value over a 30-year time frame for a range of forest recovery and biofuel production scenarios on abandoned agricultural land. Carbon sequestration in recovering forests is estimated based on a statistical analysis of tropical and temperate studies on marginal land. GHGs offset by biofuel production are analyzed for five different production pathways. We find that forest recovery is superior to low-yielding biofuel production scenarios such as oil palm and corn. Biofuel production scenarios with high yields, such as sugarcane or high-yielding energy grasses, can be comparable or superior to natural forest succession and to reforestation in some cases. This result stands in contrast to previous research suggesting that restoring degraded ecosystems to their native state is generally superior to agricultural production in terms of GHG mitigation. Further work is needed on carbon stock changes in forests, soil carbon dynamics, and bioenergy crop production on degraded/abandoned agricultural land. This finding also emphasizes the need to consider the full range of social, economic, and ecological consequences of land-use policies.
  • Authors:
    • Ren, T.
    • Zhou, T.
    • Gao, W.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: The quantity and stability of soil organic matter (SOM) associated with soil aggregates are affected by tillage management, which can be characterized potentially using the technique of thermal analysis. In this study, we evaluated the concentration and thermal stability of SOM occulted with various aggregate classes under no-tillage (NT) and moldboard plow (MP) treatments using thermogravimetry (TG) and differential scanning calorimetry (DSC). Soil samples were collected 10 yr after tillage experiment was started. The results showed that conversion from MP to NT significantly increased SOM concentration and the proportion of large macro-aggregates (>2 mm) in the 0- to 5-cm soil layer. For all aggregate classes the derivatives of thermogravimetry curves (DTG) had three weight loss peaks near 100, 350, and 500°C, and one endothermic peak and three exothermic peaks in the DSC curves. No differences in ignition temperature, peak position, and ending temperature of SOM combustion were observed between tillage treatments and among the soil layers. For both tillage systems, the proportion of thermal labile SOM (weight loss in 200-400°C accounting for that in 200-550°C, Exo1/Exotot) and energy densities (ED) of SOM (energy release per unit SOM) declined with decreasing aggregate size in the 0- to 20-cm soil layer. Moreover, TG-T50 (the temperature resulting in 50% of SOM loss) correlated negatively to aggregate size, but DSC-T50 (the temperature at which 50% of energy resulting from organic matter combustion release) correlated positively to aggregate size. Compared with MP management, NT management improved quantity but decreased thermal stability of SOM in aggregates in the 0- to 5-cm layer, which was indicated by the greater weight loss at combustion, higher Exo1/Exotot ratio, greater energy densities and lower TG-T50. No tillage also led to increased stratification ratios of thermal labile and thermal recalcitrant SOM.