• Authors:
    • Walter,Katja
    • Don,Axel
    • Flessa,Heinz
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 4
  • Year: 2015
  • Summary: Wood from short rotation coppices (SRCs) is discussed as bioenergy feedstock with good climate mitigation potential inter alia because soil organic carbon (SOC) might be sequestered by a land-use change (LUC) from cropland to SRC. To test if SOC is generally enhanced by SRC over the long term, we selected the oldest Central European SRC plantations for this study. Following the paired plot approach soils of the 21 SRCs were sampled to 80cm depth and SOC stocks, C/N ratios, pH and bulk densities were compared to those of adjacent croplands or grasslands. There was no general trend to SOC stock change by SRC establishment on cropland or grassland, but differences were very site specific. The depth distribution of SOC did change. Compared to cropland soils, the SOC density in 0-10cm was significantly higher under SRC (17 +/- 2 in cropland and 21 +/- 2kgCm(-3) in SRC). Under SRC established on grassland SOC density in 0-10cm was significantly lower than under grassland. The change rates of total SOC stocks by LUC from cropland to SRC ranged from -1.3 to 1.4 MgCha(-1)yr(-1) and -0.6MgCha(-1)yr(-1) to +0.1MgCha(-1)yr(-1) for LUC from grassland to SRC, respectively. The accumulation of organic carbon in the litter layer was low (0.14 +/- 0.08 MgCha(-1)yr(-1)). SOC stocks of both cropland and SRC soils were correlated with the clay content. No correlation could be detected between SOC stock change and soil texture or other abiotic factors. In summary, we found no evidence of any general SOC stock change when cropland is converted to SRC and the identification of the factors determining whether carbon may be sequestered under SRC remains a major challenge.
  • Authors:
    • Brady,M. V.
    • Hedlund,K.
    • Rong-Gang Cong
    • Hemerik,L.
    • Hotes,S.
    • Machado,S.
    • Mattsson,L.
    • Schulz,E.
    • Thomsen,I. K.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Soil biodiversity through its delivery of ecosystem functions and attendant supporting ecosystem services - benefits soil organisms generate for farmers - underpins agricultural production. Yet lack of practical methods to value the long-term effects of current farming practices results, inevitably, in short-sighted management decisions. We present a method for valuing changes in supporting soil ecosystem services and associated soil natural capital - the value of the stock of soil organisms - in agriculture, based on resultant changes in future farm income streams. We assume that a relative change in soil organic C (SOC) concentration is correlated with changes in soil biodiversity and the generation of supporting ecosystem services. To quantify the effects of changes in supporting services on agricultural productivity, we fitted production functions to data from long-term field experiments in Europe and the United States. The different agricultural treatments at each site resulted in significant changes in SOC concentrations with time. Declines in associated services are shown to reduce both maximum yield and fertilizer-use efficiency in the future. The average depreciation of soil natural capital, for a 1% relative reduction in SOC concentration, was 144 Euro ha -1 (SD 47 Euro ha -1) when discounting future values to their current value at 3%; the variation was explained by site-specific factors and the current SOC concentration. Moreover, the results show that soil ecosystem services cannot be fully replaced by purchased inputs; they are imperfect substitutes. We anticipate that our results will both encourage and make it possible to include the value of soil natural capital in decisions.
  • Authors:
    • Meyer-Aurich, A.
    • Kern, J.
    • Ammon, C.
    • Andert, J.
    • Dicke, C.
    • Kaupenjohann, M.
  • Source: Science Article
  • Volume: 524
  • Year: 2015
  • Summary: Field studies that have investigated the effects of char materials on the emission of nitrous oxide (N2O) are still scarce. Therefore, we conducted a field trial with bio- and hydrochars and measured N2O emissions for one whole year. It was hypothesised that the incorporation of chars reduces the emissions of N2O. Chars were produced by pyrolysis and hydrothermal carbonisation (HTC) using either maize silage or wood residues as feedstock. In addition, after production chars were post-treated with digestate in order to accelerate the ageing process of the chars. Chars and digestate were applied to the soil to raise the C content. Emissions of N2O were measured weekly and soil samples for inorganic nitrogen (N) and soil water-content were taken once a month. Additionally, the abundance of functional marker genes from denitrification (nosZ) was determined in October 2012 and in June 2013. The treatment with pure digestate emitted the most N2O compared to the control and char treatments. However, this was significant only in one case. There were no great differences between the char treatments due to high spatial variability and gene abundance of nosZ did not differ between treatments. Overall, emissions of N2O were relatively low. This was attributed to the heterogeneous distribution of the chars and the sandy soils that did not favour the production of N2O. To conclude, the emissions of N2O were mainly influenced by temperature and precipitation and to a minor extent by the type of char and post-treatment. (C) 2015 Elsevier B.V. All rights reserved.
  • Authors:
    • Verheijen,L. M.
    • Aerts,R.
    • Brovkin,V.
    • Cavender-Bares,J.
    • Cornelissen,J. H. C.
    • Kattge,J.
    • Bodegom,P. M. van
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: Earth system models demonstrate large uncertainty in projected changes in terrestrial carbon budgets. The lack of inclusion of adaptive responses of vegetation communities to the environment has been suggested to hamper the ability of modeled vegetation to adequately respond to environmental change. In this study, variation in functional responses of vegetation has been added to an earth system model (ESM) based on ecological principles. The restriction of viable mean trait values of vegetation communities by the environment, called 'habitat filtering', is an important ecological assembly rule and allows for determination of global scale trait-environment relationships. These relationships were applied to model trait variation for different plant functional types (PFTs). For three leaf traits (specific leaf area, maximum carboxylation rate at 25°C, and maximum electron transport rate at 25°C), relationships with multiple environmental drivers, such as precipitation, temperature, radiation, and CO 2, were determined for the PFTs within the Max Planck Institute ESM. With these relationships, spatiotemporal variation in these formerly fixed traits in PFTs was modeled in global change projections (IPCC RCP8.5 scenario). Inclusion of this environment-driven trait variation resulted in a strong reduction of the global carbon sink by at least 33% (2.1 Pg C yr -1) from the 2nd quarter of the 21st century onward compared to the default model with fixed traits. In addition, the mid- and high latitudes became a stronger carbon sink and the tropics a stronger carbon source, caused by trait-induced differences in productivity and relative respirational costs. These results point toward a reduction of the global carbon sink when including a more realistic representation of functional vegetation responses, implying more carbon will stay airborne, which could fuel further climate change.
  • Authors:
    • Hierold, W.
    • Miller, B. A.
    • Koszinski, S.
    • Haelbich, H.
    • Sommer, M.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 5
  • Year: 2015
  • Summary: Spatial variation of c stocks within peatlands is an overall challenge for monitoring global c cycle processes, which is critical for responding to climate change induced by greenhouse gases (GHGs). the objective of this study was to evaluate the ability of high-resolution, minimally invasive sensor data to predict spatial variation of soil organic c (soc) stocks within highly degraded peatland soils in northeast Germany. within the rhin-Havelluch, a paludification mire that has been cultivated and drained for about 300 yr, seven fields were sampled by soil cores up to 2 m in depth, nine points for each field. soil horizons were examined for dry bulk density, soil organic c content (socc), and thickness to calculate soc stocks and to test for relationships with overall peat thickness, elevation, and electrical conductivity (eca). elevation was determined by light detection and ranging (LIDAR) and eca by an eM38dd, both producing maps of high resolution (1 m). soil organic c density (socd) was related to elevation, eca, and peat thickness. Based on these relationships, maps of socd were produced. within field variation of socd was high, which could be modeled by use of the covariate maps. if available, eca maps can improve the prediction of socd based on elevation. Modeling peat thickness based on sensor data needs additional research, but seems to be a valuable covariate in digital soil mapping. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.
  • Authors:
    • Queiros,J.
    • Malca,J.
    • Freire,F.
  • Source: Journal of Cleaner Production
  • Volume: 99
  • Year: 2015
  • Summary: This article presents a life-cycle assessment (LCA) of rapeseed produced in Central Europe (France, Germany and Poland), addressing different fertilization and management practices. Two alternative fertilization scenarios were compared (on the basis of the most common fertilizer types used in Europe, namely nitrogen, phosphate P 2O 5, and potash K 2O fertilizers) and two different scenarios of soil management practices were assessed (taking into account climate and soil type prevalent in each region). Six environmental impact categories were investigated: abiotic depletion; global warming; acidification; eutrophication; ozone layer depletion; and photochemical oxidation. Results showed that the choice of fertilizer type had significant implications in the environmental impacts. Calcium ammonium nitrate (CAN) manufacturing had considerably higher greenhouse gas emissions than urea production, due to the use of nitric acid in the former. In terms of field emissions, ammonia and nitrate released following the application of nitrogen fertilizers dominated the acidification and eutrophication impacts. Nitrogen-phosphorus-potassium (NPK) compounds showed particularly high impacts in terms of photochemical oxidation, as a result of sulfur dioxide emissions from manufacturing. The remaining fertilizers (P 2O 5 and K 2O) hardly contributed to the impacts. Soil carbon change associated with different agricultural management practices significantly contributed to the greenhouse gas (GHG) intensity of rapeseed production, but important soil carbon stock variations were calculated: between 938 (release) and 271 kg CO 2eq/1000 kg dry seeds (sequestration) due to different standard soil organic carbon contents in the three rapeseed production systems and alternative tillage methods in the reference scenarios of land management.
  • Authors:
    • Ramirez,T.
    • Meas,Y.
    • Dannehl,D.
    • Schuch,I.
    • Miranda,L.
    • Rocksch,T.
    • Schmidt,U.
  • Source: Journal of Cleaner Production
  • Volume: 104
  • Year: 2015
  • Summary: The water and carbon footprint of the presented dried tomato value chain is compared to the conventional process. The coupling of pre- and post-harvest processes, namely growing and drying respectively, is analyzed for resource consumption optimization. The growing system of tomatoes ( Solanum lycopersicon L. cv, Pannovy) in an energy efficient greenhouse (operating as a solar thermal collector) is databased; while the post-harvest process consists of a model-based solar drying system. The thermodynamic operation zones (temperature, humidity and enthalpy) are detailed to apply energy interaction between both processes. The results of the monthly record of a season show that the water footprint was reduced from 91 to 51.1 L kg -1 with a standard deviation from 53.2 to 12.4 L kg -1. The carbon footprint was reduced from 40.2 to 11 kg kg -1 with a standard deviation from 23.9 to 11.4 kg carbon dioxide kg -1. From the observed variation from monthly values, the relevance of the seasonal effect on resources needed for implementing process improvements is highlighted. The use of renewable energy and energy efficiency concepts is shown to have a positive impact when applied at industrial level in 'compound industries' that share sub-processes in the value chains.
  • Authors:
    • Steffens, D.
    • Azam, F.
    • Koyro, H. W.
    • Haider, G.
    • Muller, C.
    • Kammann, C.
  • Source: Regular Article
  • Volume: 395
  • Issue: 1/2
  • Year: 2015
  • Summary: Aims: Biochar (BC) and humic acid product (HAP) soil amendments may improve plant performance under water-limited conditions. Our aim was to investigate if BC and HAP amendments, alone or in combination, will have positive and synergistic effects. Methods: A three-factorial fully randomized study was carried out in the greenhouse for 66 days, including the factors 'BC', 'HAP' and 'water regime'. Maize ( Zea mays var. 'Amadeo' DKC-3399) was grown in pots (6 kg sandy soil pot -1) amended with/without BC (0, 1.5 and 3%; w/ w) and with/without HAP (0 or an equivalent of 8 kg ha -1). Two water regimes, limited and frequent (H 2O limit , H 2O frequ ), were applied after day 28 following seedling establishment at 60% water holding capacity (WHC). In the H 2O limit treatment, the soil water content was allowed to drop until wilting symptoms became visible (25-30% WHC) while in H 2O frequ the WHC was brought to 60% of the maximum on a daily basis Results BC but not HAP, added alone or in combination with BC, significantly increased the biomass yield and the water and N use efficiency of plants at both water regimes. The BC-mediated relative increase in the yield was equal with both watering regimes, refuting initial hypotheses. BC had generally a stimulating effect on water relations and photosynthesis, it increased the relative water content and the leaf osmotic potential, decreased the stomatal resistance and stimulated the leaf gas exchange (transpiration). Both, BC and pure HAP addition, stimulated photosynthesis by increasing the electron transport rate (ETR) of photosystem II (PSII) and of the ratio between effective photochemical quantum yield to non-photochemical quenching (Y(II)/Y(NPQ)), revealing reduced heat dissipation. Conclusions: Biochar use in poor sandy soils can improve plant growth by improving soil-plant water relations and photosynthesis under both H 2O frequ and H 2O limit conditions. HAP loading, however, did not improve the effect of biochar or vice versa.
  • Authors:
    • Stinner, P.
  • Source: Energy, Sustainability and Society
  • Volume: 5
  • Issue: 4
  • Year: 2015
  • Summary: Background: Energy crops are of considerable importance for biogas production, especially in Germany. The main energy crops for that purpose are corn silage, grass silage, whole crop grain silage and other non-legume crops. The reason for preferring these crops is their high yield, which not only results in high yields of biogas per hectare but also in a high mitigation of greenhouse gases in the course of replacing fossil energy. This article aims to show an additional effect exerted on energy yield and mitigation of greenhouse gases by the use of legume energy crops. The symbiotic nitrogen fixation (SNF) of legumes compensates inorganic N fertilizer in conventional farms, if the digestate is applied as a fertilizer to the non-legume cash crops. The production of chemical N fertilizer is very energy intensive and leads to emissions of greenhouse gases from fossil energy consumption and from nitrous oxide generation. So, the creation of an effective organic fertilizer with nitrogen from biological N 2 fixation is a further energy add-on effect to the reduction of greenhouse gas emissions. Methods: For this article, data with regard to the SNF of legumes obtained in field experiments at the research station at Gladbacherhof (University of Giessen) from 2002 to 2005 were re-calculated and compared with data concerning energy need and greenhouse gas emissions in the process of producing mineral nitrogen fertilizer. In addition to the possible methane yield of these substrates, the saving in energy and greenhouse gas emissions by substituting mineral fertilizers is shown. Results: As a result, the possible replacement of primary energy by SNF of clover grass leys is calculated to be approximately less than 6.4 MWh ha -1 a -1. This is a yield that is reached in addition to the methane production, i.e. a possible reduction of greenhouse gas emissions through SNF per hectare of clover grass leys of more than 2 t CO 2 equivalents ha -1 a -1 can be achieved. Conclusions: Based on these results, it can be recommended to evaluate energy crops in a more holistic way. For legumes, the effect of SNF needs to be included into the energy and greenhouse balance.
  • Authors:
    • Vogel, A.
    • Strecker, T.
    • Steinauer, K.
    • Richter, A.
    • Ramirez, N.
    • Pierce, S.
    • Rong, J.
    • HongYan, G.
    • FuXun, A.
    • Tilman, D.
    • Scheu, S.
    • Reich, P.
    • Power, S.
    • Roscher, C.
    • Niklaus, P.
    • Manning, P.
    • Milcu, A.
    • Thakur, M.
    • Eisenhauer, N.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Soil microbial biomass is a key determinant of carbon dynamics in the soil. Several studies have shown that soil microbial biomass significantly increases with plant species diversity, but it remains unclear whether plant species diversity can also stabilize soil microbial biomass in a changing environment. This question is particularly relevant as many global environmental change (GEC) factors, such as drought and nutrient enrichment, have been shown to reduce soil microbial biomass. Experiments with orthogonal manipulations of plant diversity and GEC factors can provide insights whether plant diversity can attenuate such detrimental effects on soil microbial biomass. Here, we present the analysis of 12 different studies with 14 unique orthogonal plant diversity * GEC manipulations in grasslands, where plant diversity and at least one GEC factor (elevated CO 2, nutrient enrichment, drought, earthworm presence, or warming) were manipulated. Our results show that higher plant diversity significantly enhances soil microbial biomass with the strongest effects in long-term field experiments. In contrast, GEC factors had inconsistent effects with only drought having a significant negative effect. Importantly, we report consistent non-significant effects for all 14 interactions between plant diversity and GEC factors, which indicates a limited potential of plant diversity to attenuate the effects of GEC factors on soil microbial biomass. We highlight that plant diversity is a major determinant of soil microbial biomass in experimental grasslands that can influence soil carbon dynamics irrespective of GEC.