141. Conservation tillage systems: a review of its consequences for greenhouse gas emissions

• Authors:
  • Smith, P.
  • Williams, M.
  • Forristal, D.
  • Lanigan, G.
  • Osborne, B.
  • Abdalla, M.
  • Jones, M. B.
• Source: Soil Use and Management
• Volume: 29
• Issue: 2
• Year: 2013
• Summary: Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.

142. Valuing the carbon sequestration potential for European agriculture

• Authors:
  • De Nocker, L.
  • Aertsens, J.
  • Gobin, A.
• Source: Land Use Policy
• Volume: 31
• Year: 2013
• Summary: Purpose: This paper aims at indicating the potential of agricultural measures in sequestering carbon as an option for climate change mitigation. The related value for society is estimated. Principle results: Agricultural practices like agroforestry, introducing hedges, low and no tillage and cover crops have an important potential to increase carbon sequestration. The total technical potential in the EU-27 is estimated to be 1566 million tonnes CO2-equivalent per year. This corresponds to 37% of all CO2-equivalent emissions in the EU in 2007. The introduction of agroforestry is the measure with the highest potential, i.e. 90% of the total potential of the measures studied. Taking account only of the value for climate change mitigation, the introduction of agroforestry is estimated to have a value of 282 euro/ha in 2012 that will gradually increase to 1007 euro/ha in 2030. Major conclusions: This implies that there is a huge potential which represents an important value for society in general and for the agricultural sector in specific. At the European level, only in the last few years policy makers have recognized the important benefits of agroforestry. In their rural development programmes some European countries now support farmers to introduce agroforestry. But still the current level of support is only a small fraction of the societal value of agroforestry. If this value would be fully recognized by internalizing the positive externality, we expect that agroforestry will be introduced to a very large extent in the next decades, in Europe and the rest of the world, and this will importantly change the rural landscapes. (C) 2012 Elsevier Ltd. All rights reserved.

143. Greenhouse gas emissions and nutrient supply rates in soil amended with biofuel production by-products

• Authors:
  • Schoenau, J. J.
  • Alotaibi, K. D.
• Source: Biology and Fertility of Soils
• Volume: 49
• Issue: 2
• Year: 2013
• Summary: Ethanol production results in distiller grain, and biodiesel produces glycerol as by-product. However, there is limited information on effects of their addition on evolution of N2O and CO2 from soils, yet it is important to enable our understanding of impacts of biofuel production on greenhouse gas budgets. The objective of this study was to evaluate the direct effects of adding wet distillers grain (WDG), thin stillage (TS), and glycerol at three rates on greenhouse gas emissions (N2O and CO2) and nutrient supply rates in a cultivated soil from the Canadian prairies. The WDG and TS application rates were: 100, 200, or 400 kg N ha(-1), whereas glycerol was applied at: 40, 400, or 4,000 kg C ha(-1) applied alone (G -aEuro parts per thousand N) or in a combination with 300 kg N ha(-1) (G + N). In addition, conventional amendments of urea (UR) and dehydrated alfalfa (DA) were added at the same rates of total N as the by-products for comparative purposes. The production of N2O and CO2 was measured over an incubation period of 10 days in incubation chambers and Plant Root Simulator (TM) resin membrane probes were used to measure nutrient (NH (4) (+) -N, NO (3) (-) -N, and PO (4) (-3) -P) supply rates in the soil during incubation. Per unit of N added, urea tended to result in the greatest N2O production, followed by wet distillers grain and thin stillage, with glycerol and dehydrated alfalfa resulting in the lowest N2O production. Cumulative N2O production increased with increasing the rate of N-containing amendments and was the highest at the high rate of UR treatment. Addition of urea with glycerol contributed to a higher rate of N2O emission, especially at the low rate of glycerol. The DA and WDG resulted in the greatest evolution of CO2 from the soil, with the thin stillage resulting in less CO2 evolved per unit of N added. Addition of N fertilizer along with glycerol enhanced microbial activity and decomposition. The amendments had significant impacts on release of available nutrient, with the UR treatments providing the highest NO (3) (-) -N supply rate. The TS treatments supplied the highest rate of NH (4) (+) -N, followed by WDG compared to the other amendments. The WDG treatments were able to provide the greatest supply of PO (4) (-3) -P supply in comparison to the other amendments. Microbial N immobilization was associated with glycerol treatments applied alone. This study showed that the investigated biofuel by-products can be suitable soil amendments as a result of their ability to supply nutrients and N2O emissions that did not exceed that of the conventional urea fertilizer.

144. Biochar affects the structure rather than the total biomass of microbial communities in temperate soils

• Authors:
  • Zechmeister-Boltenstern, S.
  • Stahr, K.
  • Zehetner, F.
  • Wimmer, B.
  • Kitzler, B.
  • Rempt, F.
  • Watzinger, A.
  • Anders, E.
  • Soja, G.
• Source: Agricultural and Food Science
• Volume: 22
• Issue: 4
• Year: 2013
• Summary: Biochar application is a promising strategy for sequestering carbon in agricultural soils and for improving degraded soils. Nonetheless, contradictory and unsettled issues remain. This study investigates whether biochar influences the soil microbial biomass and community structure using phospholipid fatty acid (PLFA) analysis. We monitored the effects of four different types of biochar on the soil microbial communities in three temperate soils of Austria over several months. A greenhouse experiment and two field experiments were conducted. The biochar application did not significantly increase or decrease the microbial biomass. Only the addition of vineyard pruning biochar pyrolysed at 400 degrees C caused microbial biomass to increase in the greenhouse experiment. The biochar treatments however caused shifts in microbial communities (visualized by principal component analysis). We concluded that the shifts in the microbial community structure are an indirect rather than a direct effect and depend on soil conditions and nutrient status.

145. Uncertainty in simulating wheat yields under climate change

• Authors:
  • Priesack, E.
  • Palosuo, T.
  • Osborne, T. M.
  • Olesen, J. E.
  • O'Leary, G.
  • Nendel, C.
  • Kumar, S. Naresh
  • Mueller, C.
  • Kersebaum, K. C.
  • Izaurralde, R. C.
  • Ingwersen, J.
  • Hunt, L. A.
  • Hooker, J.
  • Heng, L.
  • Grant, R.
  • Goldberg, R.
  • Gayler, S.
  • Doltra, J.
  • Challinor, A. J.
  • Biernath, C.
  • Bertuzzi, P.
  • Angulo, C.
  • Aggarwal, P. K.
  • Martre, P.
  • Basso, B.
  • Brisson, N.
  • Cammarano, D.
  • Rotter, R. P.
  • Thorburn, P. J.
  • Boote, K. J.
  • Ruane, A. C.
  • Hatfield, J. L.
  • Jones, J. W.
  • Rosenzweig, C.
  • Ewert, F.
  • Asseng, S.
  • Ripoche, D.
  • Semenov, M. A.
  • Shcherbak, I.
  • Steduto, P.
  • Stoeckle, C.
  • Stratonovitch, P.
  • Streck, T.
  • Supit, I.
  • Tao, F.
  • Travasso, M.
  • Waha, K.
  • Wallach, D.
  • White, J. W.
  • Williams, J. R.
  • Wolf, J.
• Source: Nature Climate Change
• Volume: 3
• Issue: 9
• Year: 2013
• Summary: Projections of climate change impacts on crop yields are inherently uncertain(1). Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate(2). However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models(1,3) are difficult(4). Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development and policy making.

146. Use of Biochar and Oxidized Lignite for Reconstructing a Functioning Topsoil: Plant Growth Response and Soil Nutrient Concentrations

• Authors:
  • Young, M. A.
  • Roy, J. L.
  • Bekele, A.
• Source: Soil Science
• Volume: 178
• Issue: 7
• Year: 2013
• Summary: Topsoil (TS) shortage often limits the successful reclamation of older mined sites. We evaluated the effectiveness of one-time application of biochar or oxidized lignite (humalite) alone or in combination with a mix of conventional organic materials to reconstruct functioning TS using subsoil (SS) as a substrate. Biochar or humalite carbon (C) represented a stable form of C, whereas C from a mix of sawdust, wheat straw, and alfalfa (labile organic mix (LOM)) represented the labile C fraction. The amount and composition of organic amendment mix were determined so that organic C levels of reconstructed TS would be equivalent to that of the native TS in the long-term. Three SS substrates differing in texture (clay, loam, and sand) and organic C levels were used in the study. We used field pea (Pisum sativum L.) and barley (Hordeum vulgare L.) as test crops in rotation in four sequential greenhouse studies. All treatments except the control SS and TS received supplemental fertilizer nutrients. Plant biomass yield and tissue concentrations were evaluated at the end of each study, whereas soil nutrient levels were assessed at the end of Study II and Study IV. Labile organic mix amendment alone was superior in biomass production relative to any of the other treatments at the early stages of the study. Cumulative biomass yield of SS amended with either biochar or humalite in the presence of LOM was statistically identical for clay and sand soils. These values were also statistically indistinguishable from the fertilized native TS control treatment for the clay soil but not for the sand soil. Humalite application at a high rate (76 g/kg soil) increased soil CEC, decreased soil pH and P concentration, and increased both soil and plant tissue B concentrations. Our data show that a functioning TS can be reconstructed using either biochar or humalite in the presence of LOM and adequate supplemental fertilizers particularly N and P. Detailed characterization of organic amendments is recommended to avoid undesirable effects emanating from their use. Field-based long-term studies are needed to confirm the longevity of benefits of using these amendments.

147. Crop Residue Removal for Bioenergy Reduces Soil Carbon Pools: How Can We Offset Carbon Losses?

• Authors:
  • Blanco-Canqui, H.
• Source: BioEnergy Research
• Volume: 6
• Issue: 1
• Year: 2013
• Summary: Crop residue removal for bioenergy can deplete soil organic carbon (SOC) pools. Management strategies to counteract the adverse effects of residue removal on SOC pools have not been, however, widely discussed. This paper reviews potential practices that can be used to offset the SOC lost with residue removal. Literature indicates that practices including no-till cover crops, manure and compost application, and return of biofuel co-products increase SOC pools and may thus be used to offset some SOC loss. No-till rotations that include semi-perennial grasses or legumes also offer a promise to promote soil-profile C sequestration and improve soil resilience after residue removal. No-till cover crops can sequester between 0.10 and 1 Mg ha(-1) per year of SOC relative to no-till without cover crops, depending on cover crop species, soil type, and precipitation input. Animal manure and compost contain about 15 % of C and thus their addition to soil can enhance SOC pools and boost soil biological activity. Similarly, application of biofuel co-products such as biochar, which contain between 45 % and 85 % of C depending on the feedstock source and processing method, can enhance long-term C sequestration. These mitigation strategies may maintain SOC pools under partial residue removal in no-till soils but are unlikely to replace all the SOC lost if residue is removed at excessive rates. More field research and modeling efforts are needed to assess the magnitude at which the different mitigation strategies can overcome SOC loss with crop residue removal.

148. Greenhouse gas emissions from rape seed cultivation for FAME production in Poland

• Authors:
  • Jarosz, Z.
  • Faber, A.
  • Borzecka-Walker, M.
  • Syp, A.
  • Pudelko, R.
• Source: Journal: Food, Agriculture and Environment (JFAE)
• Volume: 11
• Issue: 1
• Year: 2013
• Summary: The production of bio diesel from rape seed, in accordance with Directive 2009/28/EC (RED), requires estimation on greenhouse gas (GHG) emissions in the life cycle of bio fuels and reduction size in comparison to diesel as fossil fuel. The study sought a reduction in GHG emissions from agriculture, in the full life cycle of Fatty Acid Methyl Esters (FAME) by optimisation of nitrogen fertilisation of rape seed, the selection of fertilisers with lower emissions arising from their production and increased organic carbon sequestration in the soil by the use of reduced or no tillage (direct sowing). It was found that an optimisation of the nitrogen (N) dose and manipulations of fertiliser N type does not guarantee a 50% reduction in GHG emissions. The reduction of GHG emissions under reduced tillage, which increases the organic carbon sequestration in the soil, is achievable only at a dose of 150 kg N ha(-1) in the form of a urea ammonium nitrate (UAN) solution or mixture of ammonium nitrate + ammonium sulphate. The increase of organic carbon sequestration in the soil through the conversion of conventional oilseed rape cultivation to a no tillage system increases the reduction of GHG emissions by 58-63% at a dose of 150 kg N ha(-1) and 54-59% at a dose of 180 kg N ha(-1).

149. Trends in organic carbon and nitrogen contents in agricultural soils in Bavaria (south Germany) between 1986 and 2007

• Authors:
  • Capriel, P.
• Source: European Journal of Soil Science
• Volume: 64
• Issue: 4
• Year: 2013
• Summary: In the last 60 years traditional agriculture in industrialized European countries, which had initially been dependent on available natural resources, has shifted towards a massive intensification of nutrient turnover because of cheap energy and low-cost synthetic fertilizers. At the same time farm structure has undergone profound changes, resulting in an increase in the number of specialized farms to the detriment of traditional non-specialized ones. All these trends have had a significant impact on agricultural management. The intensification of agricultural management together with climate change could affect the quantity and quality of soil organic matter (SOM). That could imply decreasing soil fertility, reduced harvest yields, increasing nutrient losses and additional greenhouse gas emission. In order to measure the long-term development of SOM in agricultural soils a monitoring programme was initiated in Bavaria in 1986. The measurements are based on 92 representative plots located on cropland and 21 plots located on managed permanent grassland. Between 1986 and 2007 the monitoring plots have been sampled four times. The monitoring results suggest a decrease of soil organic carbon content, total nitrogen content and C:N ratio in cropland as well as in grassland in Bavaria between 1986 and 2007. Crops and organic fertilizers are together with the initial SOM content the main causes of the observed changes in SOM quantity and quality. A climatic effect could be neither proved nor excluded. The results in Bavaria are consistent with the reported changes in organic carbon of agricultural soils in Austria, Belgium, France, the Netherlands and England. In Bavaria we should expect declining SOM stocks, particularly soil organic carbon, in agricultural soils if the supply of organic matter remains constant or even decreases.

150. Organic grain cropping systems to enhance ecosystem services

• Authors:
  • Spargo, J. T.
  • Teasdale, J. R.
  • Mirsky, S. B.
  • Cavigelli, M. A.
  • Doran, J.
• Source: Renewable Agriculture and Food Systems
• Volume: 28
• Issue: 2
• Year: 2013
• Summary: Organic grain cropping systems can enhance a number of ecosystem services compared with conventional tilled (CT) systems. Recent results from a limited number of long-term agricultural research (LTAR) studies suggest that organic grain cropping systems can also increase several ecosystem services relative to conventional no-till (NT) cropping systems: soil C sequestration and soil N fertility (N mineralization potential) can be greater while global warming potential (GWP) can be lower in organic systems that use animal manures and cover crops compared with conventional NT systems. However, soil erosion from organic systems and nitrous oxide (N2O, a greenhouse gas) emissions from manure-based organic systems appear to be greater than from conventional NT systems, though data are limited. Also, crop yields, on average, continue to be lower and labor requirements greater in organic than in both tilled and NT conventional systems. Ecosystem services provided by organic systems may be improved by expanding crop rotations to include greater crop phenological diversity, improving nutrient management, and reducing tillage intensity and frequency. More diverse crop rotations, especially those that include perennial forages, can reduce weed pressure, economic risk, soil erosion, N2O emissions, animal manure inputs, and soil P loading, while increasing grain yield and soil fertility. Side-dressing animal manures in organic systems may increase corn nitrogen use efficiency and also minimize animal manure inputs. Management practices that reduce tillage frequency and intensity in organic systems are being developed to reduce soil erosion and labor and energy needs. On-going research promises to further augment ecosystem services provided by organic grain cropping systems.