• Authors:
    • Ruser, R.
    • Muller, T.
    • Fiedler, S.
    • Buegger, F.
    • Palmer, I.
    • Pfab, H.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 150
  • Year: 2012
  • Summary: Arable soils are a major source of the climate relevant trace gas nitrous oxide (N 2O). Although N 2O emissions from soils increase with the amount of N-fertilizer, there is still a lack of data for intensively fertilized systems, such as vegetable production. We investigated the effect of an ammonium sulfate nitrate (ASN) fertilization either placed or broadcast applied combined with a nitrification inhibitor (3,4-dimethylepyrazole phosphate (DMPP)) on soil surface N 2O fluxes as compared to conventional broadcast ASN fertilization in a lettuce-cauliflower rotation over two years of measurement. Except for a lower cauliflower yield in the second experimental year with placed fertilization, no differences in yields between the fertilized treatments were observed. Annual cumulative N 2O emissions of the conventionally fertilized treatment were 8.8 and 4.7 kg N 2O-N ha -1 yr -1 for the first and second experimental year, respectively, indicating a high inter-annual variability. The addition of the nitrification inhibitor significantly reduced N 2O emissions during the cropping season and also during the winter period, resulting in an annual reduction of 45 and 40% as compared to the conventionally fertilized (CONV) treatment. The reason for the lower N 2O release in the DMPP treatment as compared to the conventionally fertilized treatment remained unclear. Since we did not find any significant differences in the mineral N pools during periods with distinctive inhibition, this can be ruled out as reason for the lower N 2O release in the DMPP treatment. We found lower soil respiration in the DMPP treatment during several months starting about six weeks after fertilizer application. In contrast to the treatment with nitrification inhibitor, the placed fertilization as an N-depot (fertilizer bands inserted into the soil) did not reduce annual N 2O emissions, although the ratio of ammonium (NH 4+) to nitrate (NO 3-) in the first weeks after N-application indicate inhibition of nitrification in the fertilizer depot. We assume that, even though NH 4+ concentrations in the depots were high, toxicity was not sufficient for a complete inhibition of microbial activity in the surrounding of the depots, resulting in considerable N 2O production. The emission factors calculated for CONV treatment were 1.6 and 0.8% for the first and second experimental year, respectively. For the treatment with nitrification inhibitor (NI), they were only 0.9 and 0.5%; for the treatment with placed fertilization as an N-depot (DEPOT) 2.0 and 0.8%. They were thus within the range proposed by the guidelines of the IPCC (2006). However, although the N-input related N 2O emission factors were within the range proposed by the guidelines of the IPCC, the absolute N 2O emissions from the intensively fertilized vegetable field were high. For effective, but environmentally sound vegetable production, a deeper understanding of nitrification inhibitory strategies is necessary.
  • Authors:
    • Steffens, D.
    • Qayyum, M. F.
    • Reisenauer, H. P.
    • Schubert, S.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: Application of biochars to soils may stabilize soil organic matter and sequester carbon (C). The objectives of our research were to study in vitro C mineralization kinetics of various biochars in comparison with wheat straw in three soils and to study their contribution to C stabilization. Three soils (Oxisol, Alfisol topsoil, and Alfisol subsoil) were incubated at 25°C with wheat straw, charcoal, hydrothermal carbonization coal (HTC), low-temperature conversion coal (LTC), and a control (natural organic matter). Carbon mineralization was analyzed by alkali absorption of CO 2 released at regular intervals over 365 d. Soil samples taken after 5 and 365 d of incubation were analyzed for soluble organic C and inorganic N. Chemical characterization of biochars and straw for C and N bonds was performed with Fourier transformation spectroscopy and with the N fractionation method, respectively. The LTC treatment contained more N in the heterocyclic-bound N fraction as compared with the biochars and straw. Charcoal was highly carbonized when compared with the HTC and LTC. The results show higher C mineralization and a lower half-life of straw-C compared with biochars. Among biochars, HTC showed some C mineralization when compared with charcoal and LTC over 365 d. Carbon mineralization rates were different in the three soils. The half-life of charcoal-C was higher in the Oxisol than in the Alfisol topsoil and subsoil, possibly due to high Fe-oxides in the Oxisol. The LTC-C had a higher half-life, possibly due to N unavailability. We conclude that biochar stabilization can be influenced by soil type.
  • Authors:
    • Herrmann, A.
    • Techow, A.
    • Pacholski, A.
    • Quakernack, R.
    • Taube, F.
    • Kage, H.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 160
  • Year: 2012
  • Summary: Anaerobic co-fermentation of animal slurries and crop silages leads to new types of biogas residues with an uncertain fertilizer value. Ammonia volatilization losses and crop productivity after supplying co-fermented biogas residues were investigated at a marshland site in Northern Germany. Due to the ecological risks of monocultures, maize ( Zea mays) in monoculture as the dominant biogas crop in the marsh was tested against a crop rotation (maize, wheat ( Triticum aestivum), Italian ryegrass ( Lolium multiflorum)) and perennial ryegrass ( Lolium perenne). Biogas residues, applied by trail hoses, and CAN (mineral fertilizer) were used as nitrogen fertilizers. Ammonia losses at all application dates were investigated by an approach including passive flux samplers and a calibrated dynamic chamber method. Simultaneously a micrometeorological technique was used as a reference. A comparison of methods showed a close correlation ( r2=0.92) between micromet and passive flux sampler techniques. Ammonia volatilization losses (on average 15% NH 4+-N applied) occurred mainly within the first 10 h. Concomitant with high ammonia losses, a significant yield depression of 5 t DM ha -1 for ryegrass fertilized by biogas residues compared to CAN was observed. Little or no affect of biogas was observed for maize and wheat. The crop rotation had yields (34 t DM ha -1 2 year -1) that were comparable with the maize monoculture (31 t DM ha -1 2 year -1).
  • Authors:
    • Lutzow, M. von
    • Schilling, B.
    • Reischl, A.
    • Haug, S.
    • Hangen, E.
    • Geuss, U.
    • Sporlein, P.
    • Wiesmeier, M.
    • Kogel-Knabner, I.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Precise estimations of soil organic carbon (SOC) stocks are of decided importance for the detection of C sequestration or emission potential induced by land use changes. For Germany, a comprehensive, land use-specific SOC data set has not yet been compiled. We evaluated a unique data set of 1460 soil profiles in southeast Germany in order to calculate representative SOC stocks to a depth of 1 m for the main land use types. The results showed that grassland soils stored the highest amount of SOC, with a median value of 11.8 kg m -2, whereas considerably lower stocks of 9.8 and 9.0 kg m -2 were found for forest and cropland soils, respectively. However, the differences between extensively used land (grassland, forest) and cropland were much lower compared with results from other studies in central European countries. The depth distribution of SOC showed that despite low SOC concentrations in A horizons of cropland soils, their stocks were not considerably lower compared with other land uses. This was due to a deepening of the topsoil compared with grassland soils. Higher grassland SOC stocks were caused by an accumulation of SOC in the B horizon which was attributable to a high proportion of C-rich Gleysols within grassland soils. This demonstrates the relevance of pedogenetic SOC inventories instead of solely land use-based approaches. Our study indicated that cultivation-induced SOC depletion was probably often overestimated since most studies use fixed depth increments. Moreover, the application of modelled parameters in SOC inventories is questioned because a calculation of SOC stocks using different pedotransfer functions revealed considerably biased results. We recommend SOC stocks be determined by horizon for the entire soil profile in order to estimate the impact of land use changes precisely and to evaluate C sequestration potentials more accurately.
  • Authors:
    • Zegada-Lizarazu, W.
    • Walter, K.
    • Valentine, J.
    • Djomo, S. Njakou
    • Monti, A.
    • Mander, U.
    • Lanigan, G. J.
    • Jones, M. B.
    • Hyvonen, N.
    • Freibauer, A.
    • Flessa, H.
    • Drewer, J.
    • Carter, M. S.
    • Skiba, U.
    • Hastings, A.
    • Osborne, B.
    • Don, A.
    • Zenone, T.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha(-1) yr(-1) for poplar and willow and 0.66 Mg soil C ha(-1) yr(-1) for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.
  • Authors:
    • Emmerling, C.
    • Felten, D.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 175
  • Issue: 5
  • Year: 2012
  • Summary: Bioenergy is becoming an important option in Global Change mitigation policy world-wide. In agriculture, cultivation of energy crops for biodiesel, biogas, or bioethanol production received considerable attention in the past decades. Beyond this, the cultivation of Miscanthus, used as solid fuel for combustion, may lead to an increase in soil organic matter content compared to other agricultural land use, since C-sequestration potential in soils of Miscanthus crops is high due to, e.g., high amounts of harvest residues. This may indirectly contribute to a reduction of atmospheric CO2 concentration. The objective of the present work was to investigate the development of soil organic carbon and Miscanthus-derived C contents, as well as to estimate carbon stocks in soils cultivated with Miscanthus using 13C-natural-abundance technique. The investigations were carried out in relation to soil depth up to 150?cm in a sequence of 2, 5, and 16 y of cultivation relative to a reference soil cultivated with cereals. Amounts of total organic C (TOC) and Miscanthus-derived C (Miscanthus-C) increased with increasing duration of cultivation. For example, TOC increased from 12.8 to 21.3 g C?kg1 after 16 y of cultivation at the depth of 015?cm, whereby the portion of Miscanthus-C reached 5.8 g C?kg1. Also within deeper soil layers down to 60?cm depth a significant enhancement of Miscanthus-C was detectable even though TOC contents were not significantly enhanced. At soil depth below 60?cm, no significant differences between treatments were found for Miscanthus-C. Within 16 y of continuous commercial farming, Miscanthus stands accumulated a total of 17.7 Mg C ha1 derived from Miscanthus residues (C4-C), which is equivalent to 1.1 Mg C4-C ha1 y1. The annual surplus might function as CO2 credit within a greenhouse-gas balance. Moreover, the beneficial properties of Miscanthus cultivation combined with a low requirement on fertilization may justify the status of Miscanthus as a sustainable low-input bioenergy crop.
  • Authors:
    • Wiegel, R.
    • Claupein, W.
    • Graeff-Hoenninger, S.
    • Butterbach-Bahl, K.
    • Gauder, M.
  • Source: Web Of Knowledge
  • Volume: 4
  • Issue: 3
  • Year: 2012
  • Summary: Willow coppice, energy maize and Miscanthus were evaluated regarding their soil-derived trace gas emission potential involving a nonfertilized and a crop-adapted slow-release nitrogen (N) fertilizer scheme. The N application rate was 80 kg N ha-1 yr-1 for the perennial crops and 240 kg N ha-1 yr-1 for the annual maize. A replicated field experiment was conducted with 1-year measurements of soil fluxes of CH4, CO2 and N2O in weekly intervals using static chambers. The measurements revealed a clear seasonal trend in soil CO2 emissions, with highest emissions being found for the N-fertilized Miscanthus plots (annual mean: 50 mg C m-(2) h-1). Significant differences between the cropping systems were found in soil N2O emissions due to their dependency on amount and timing of N fertilization. N-fertilized maize plots had highest N2O emissions by far, which accumulated to 3.6 kg N2O ha-1 yr-1. The contribution of CH4 fluxes to the total soil greenhouse gas subsumption was very small compared with N2O and CO2. CH4 fluxes were mostly negative indicating that the investigated soils mainly acted as weak sinks for atmospheric CH4. To identify the system providing the best ratio of yield to soil N2O emissions, a subsumption relative to biomass yields was calculated. N-fertilized maize caused the highest soil N2O emissions relative to dry matter yields. Moreover, unfertilized maize had higher relative soil N2O emissions than unfertilized Miscanthus and willow. These results favour perennial crops for bioenergy production, as they are able to provide high yields with low N2O emissions in the field.
  • Authors:
    • Tode, J.
    • Herrmann, A.
    • Taube, F.
  • Source: Grassland - a European resource? Proceedings of the 24th General Meeting of the European Grassland Federation, Lublin, Poland, 3-7 June 2012
  • Volume: 17
  • Year: 2012
  • Summary: Land use change represents a major source of anthropogenic induced greenhouse gas emissions. A monitoring study was conducted to quantify the impact of land use systems on soil organic carbon stocks on various sites throughout Schleswig-Holstein, Northern Germany. Results revealed higher SOC stocks under grassland compared to arable cropping. Long-term maize monoculture, however, did not show lower C sequestration than arable rotations with or without maize.
  • Authors:
    • Mueller, C.
    • Eckhard, C.
    • Ratering, S.
    • Kammann, C.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: With a growing world population and global warming, we are challenged to increase food production while reducing greenhouse gas (GHG) emissions. We studied the effects of biochar (BC) and hydrochar (HC) produced via pyrolysis or hydrothermal carbonization, respectively, on GHG fluxes in three laboratory incubation studies. In the first experiment, ryegrass was grown in sandy loam mixed with equal amounts of a nitrogen-rich peanut hull BC, compost, BC+compost, double compost, or no addition (control); wetting-drying cycles and N fertilization were applied. Biochar with or without compost significantly reduced N2O emissions and did not change the CH4 uptake, whereas ryegrass yield was significantly increased. In the second experiment, 0% (control) or 8% (w/w) of BC (peanut hull, maize, wood chip, or charcoal) or 8% HC (beet chips or bark) was mixed into a soil and incubated at 65% water-holding capacity (WHC) for 140 d. Treatments included simulated plowing and N fertilization. All BCs reduced N2O emissions by similar to 60%. Hydrochars reduced N2O emissions only initially but significantly increased them after N fertilization to 302% (HC-beet) and 155% (HC-bark) of the control emissions, respectively. Large HC-associated CO2 emissions suggested that microbial activity was stimulated and that HC was less stable than BC. In the third experiment, nutrient-rich peanut hull BC addition and incubation over 1.5 yr at high WHCs did not promote N2O emissions. However, N2O emissions were significantly increased with BC after NH4 NO3 addition. In conclusion, BC reduced N2O emissions and improved the GHG-to-yield ratio under field-relevant conditions. However, the risk of increased N2O emissions with HC addition must be carefully evaluated.
  • Authors:
    • Jossi, W.
    • Zihlmann, U.
    • Heijden, M. van der
    • Anken, T.
    • Dorn, B.
  • Source: Agrarforschung Schwei
  • Volume: 18
  • Issue: 10
  • Year: 2011
  • Summary: Earthworm activity improves soil fertility. In arable crop rotations highest earthworm populations are usually found in leys. The impact of tillage system and tillage intensity on earthworm populations was studied in the two long term trials at Burgrain (Albertswil LU) and at Hausweid (Aadorf TG). At Burgrain having a crop rotation lasting six years and including a ley, no significant difference of earthworm biomass was found between ploughed plots and plots with in the sampling period 2004-2008 in the tillage system using minimum tillage (mulch drilling for oilseed rape and sowing with a rotary band cultivator rotary band seeding for silage maize) (IP extensive) compared to ploughing in both, the organic as well as the integrated production (IP intensive). In contrast, at Hausweid having a four years crop rotation at Hausweid without ley, earthworm populations differed significantly depending on tillage system and tillage intensity after 21 years of the trial. Earthworm biomass reached 330 g per m 2 in the permanent grassland adjacent to the trial whereas it was reduced by 50% in the no-till and even by 80% in the ploughed plots. Additionally, average earthworm species diversity in permanent grassland and no-till was 30% higher than in ploughed tillage system. These findings confirm the positive impact of no-till on the increase of earthworm populations and species diversity.