• Authors:
    • Mueller, T.
    • Schulz, R.
    • Moeller, K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 89
  • Issue: 2
  • Year: 2011
  • Summary: An increasing number of biogas plants (BGPs) based on digestion of dedicated energy crops have been implemented in Germany. The objectives of this study were to assess the changes in (1) the acreage of different crops (silage maize, cereals, etc.) related to the setup of the BGP, (2) nutrient flows and budgets (N, P, K) due to the implementation of the BGPs, and (3) to assess the effluent N in the overall crop N supply. Data from 14 farmers before the setup of the BGPs were compared with data after implementation. Due to the setup of the BGPs, the acreage of silage maize greatly increased and there were significant negative effects on the weighted soil humus budgets, no effects on the weighted mean N and P budgets, and a negative trend regarding the K budgets. Results concerning the N release from organic manuring to maize crops showed that one third of the farmers considerably over-fertilize maize, indicating an underestimation of short- and long-term N supply of manure N. The implementation of centralized BGPs established very intensive nutrient cycles and, in the long-term higher risks of nutrient losses and environmental pollution are expected. One very effective measure to compensate for negative effects on the soil humus budgets and nitrate leaching is an enlargement of cover cropping, which will also offer economic revenue by providing aboveground biomass for digestion. If the amounts of effluents returned to a single farm or field are not adapted to the nutrient composition of the substrates delivered to the BGP, large nutrient imbalances can result. An effective measure to get a better allocation of the available nutrients is a solid-liquid separation of the effluents, enabling a more targeted allocation of the nutrients.
  • Authors:
    • Karanisa, T.
    • Gerhards, R.
    • Brust, J.
    • Ruff, L.
    • Kipp, A.
  • Source: GESUNDE PFLANZEN
  • Volume: 63
  • Issue: 4
  • Year: 2011
  • Summary: Cover crops and under-sown crops have often been reported to have a positive impact on soil structure, soil living organisms and soil fertility. In many studies it was shown that they suppress weed populations. However, the percentage of winter annual cereals in European cropping system has strongly increased, which consequently reduced the time for growing cover crops. In this study, it was investigated if cover crops and under-sown have the capacity to reduce weed infestations also in rotations with a high percentage of winter annual cereals. Three field trials were conducted using at the University of Hohenheim from 2008 until 2010. Trifolium repens and Lolium perenne reduced weed density and weed biomass in Triticum aestivum and Triticum spelta, when they were sown as under-sown crops. Both under-sown crops had no negative effect on grain yield. Until 14 days after harvest, the under-sown crops developed a dense plant canopy. In the third experiment, Sinapis alba, Phacelia tanacetifolia, Avena strigosa and a mixture of Trifolium alexandrinum, Vicia sativa, Fagopyrum tataricum and Guizotia abyssinica were sown directly after harvest of winter wheat. Most of the cover crops emerged after few days and significantly reduced the density and biomass of emerging weeds. Sinapis alba resulted in a 93% reduction of above-ground weed biomass. Avena strigosa reduced root-biomass of weed by 97% and weed density by 90%. In order to achieve a significant weed suppression, cover crops need to emerged quickly and grow rapidly until the soil has been covered. The results of this study underline the potential of under-sown crops and cover-crops to support a sustainable and environmental friendly cropping system.
  • Authors:
    • Claupein, W.
    • Mohring, J.
    • Bühler, A.
    • Gruber, S.
  • Source: European Journal of Agronomy
  • Volume: 33
  • Issue: 2
  • Year: 2010
  • Summary: Conventional tillage systems with high soil disturbance are being steadily replaced by tillage systems with low or no soil disturbance. An approach using three methodological steps (greenhouse, deliberate seed burial and field) revealed the long-term vertical distribution and losses of a soil seed bank as effects of different tillage operations. Seeds (oilseed rape; Brassica napus L.) and seed substitutes (plastic pellets) acted as models for a seed bank. (a) A pot experiment in the greenhouse showed that emergence rates were highest in soil depths of 1-5 cm. Germination and emergence was clearly reduced in depths of 0 and 7 cm, and emergence was completely inhibited at 12 cm. About 40-50% of seeds fell dormant in 0 and 12 cm depth, while almost no seeds fell dormant in 1-7 cm depth. (b) The high-dormancy variety Smart persisted to a high extent (60% of the initial seed number), but only 8% of seeds of the low-dormancy variety Express persisted over 4.5 years, after deliberate seed burial. Seed persistence was similar in all soil depths of 0-10 cm, 10-20 cm, and 20-30 cm. (c) The field experiment lasted from 2004 to 2009 and had different tillage treatments of inversion and non-inversion tillage: stubble tillage immediately after harvest combined with primary tillage by mouldboard plough (SP), chisel plough (SC), or rototiller (SRTT); primary tillage without stubble tillage by mouldboard plough (P), chisel plough (C); or no tillage (NT). The seed bank from an artificial seed rain of 20,000 seeds m -2 was significantly higher in all treatments with immediate stubble tillage, and clearly declined over time. However, seed bank depletion was slow once a seed bank had been established. The distribution of oilseed rape seeds and plastic pellets (7000 pellets m -2 broadcast) tended to equalise over the soil layers of 0-10, 10-20 and 20-30 cm over the course of five years. Since seed bank depletion was not attributable to a specific soil depth, shallow and low disturbance tillage did not generally result in a high seed persistence. More important than the depth was the timing of tillage. Though no-till systems provided conditions for seeds to fall dormant at the soil surface to a small extent, the effect lasted only for a limited time. Seed substitutes can be well used in methodological approaches to picture movement of seeds in the soil in order to optimize tillage strategies in agricultural practice.
  • Authors:
    • Dejoux, J. F.
    • Aubinet, M.
    • Bernhofer, C.
    • Bodson, B.
    • Buchmann, N.
    • Carrara, A.
    • Cellier, P.
    • Di Tommasi, P.
    • Elbers, J. A.
    • Eugster, W.
    • Gruenwald, T.
    • Jacobs, C. M. J.
    • Jans, W. W. P.
    • Jones, M.
    • Kutsch, W.
    • Lanigan, G.
    • Magliulo, E.
    • Marloie, O.
    • Moors, E. J.
    • Moureaux, C.
    • Olioso, A.
    • Osborne, B.
    • Sanz, M. J.
    • Saunders, M.
    • Smith, P.
    • Soegaard, H.
    • Wattenbach, M.
    • Ceschia, E.
    • Beziat, P.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 139
  • Issue: 3
  • Year: 2010
  • Summary: The greenhouse gas budgets of 15 European crop sites covering a large climatic gradient and corresponding to 41 site-years were estimated. The sites included a wide range of management practices (organic and/or mineral fertilisation, tillage or ploughing, with or without straw removal, with or without irrigation, etc.) and were cultivated with 15 representative crop species common to Europe. At all sites, carbon inputs (organic fertilisation and seeds), carbon exports (harvest or fire) and net ecosystem production (NEP), measured with the eddy covariance technique, were calculated. The variability of the different terms and their relative contributions to the net ecosystem carbon budget (NECB) were analysed for all site-years, and the effect of management on NECB was assessed. To account for greenhouse gas (GHG) fluxes that were not directly measured on site, we estimated the emissions caused by field operations (EFO) for each site using emission factors from the literature. The EFO were added to the NECB to calculate the total GHG budget (GHGB) for a range of cropping systems and management regimes. N2O emissions were calculated following the IPCC (2007) guidelines, and CH4 emissions were estimated from the literature for the rice crop site only. At the other sites, CH4 emissions/oxidation were assumed to be negligible compared to other contributions to the net GHGB. Finally, we evaluated crop efficiencies (CE) in relation to global warming potential as the ratio of C exported from the field (yield) to the total GHGB. On average, NEP was negative (-284 +/- 228 gC m(-2) year(-1)), and most cropping systems behaved as atmospheric sinks, with sink strength generally increasing with the number of days of active vegetation. The NECB was, on average, 138 +/- 239 gC m(-2) year(-1), corresponding to an annual loss of about 2.6 +/- 4.5% of the soil organic C content, but with high uncertainty. Management strongly influenced the NECB, with organic fertilisation tending to lower the ecosystem carbon budget. On average, emissions caused by fertilisers (manufacturing, packaging, transport, storage and associated N2O emissions) represented close to 76% of EFO. The operation of machinery (use and maintenance) and the use of pesticides represented 9.7 and 1.6% of EFO, respectively. On average, the NEP (through uptake of CO2) represented 88% of the negative radiative forcing, and exported C represented 88% of the positive radiative forcing of a mean total GHGB of 203 +/- 253 gC-eq m(-2) year(-1). Finally, CE differed considerably among crops and according to management practices within a single crop. Because the CE was highly variable, it is not suitable at this stage for use as an emission factor for management recommendations, and more studies are needed to assess the effects of management on crop efficiency.
  • Authors:
    • van Groenigen, K. J.
    • van Kessel, C.
    • Oenema, O.
    • Velthof, G. L.
    • van Groenigen, J. W.
  • Source: European Journal of Soil Science
  • Volume: 61
  • Issue: 6
  • Year: 2010
  • Summary: Agricultural soils are the main anthropogenic source of nitrous oxide (N2O), largely because of nitrogen (N) fertilizer use. Commonly, N2O emissions are expressed as a function of N application rate. This suggests that smaller fertilizer applications always lead to smaller N2O emissions. Here we argue that, because of global demand for agricultural products, agronomic conditions should be included when assessing N2O emissions. Expressing N2O emissions in relation to crop productivity (expressed as above-ground N uptake: "yield-scaled N2O emissions") can express the N2O efficiency of a cropping system. We show how conventional relationships between N application rate, N uptake and N2O emissions can result in minimal yield-scaled N2O emissions at intermediate fertilizer-N rates. Key findings of a meta-analysis on yield-scaled N2O emissions by non-leguminous annual crops (19 independent studies and 147 data points) revealed that yield-scaled N2O emissions were smallest (8.4 g N2O-N kg-1N uptake) at application rates of approximately 180-190 kg Nha-1 and increased sharply after that (26.8 g N2O-N kg-1 N uptake at 301 kg N ha-1). If the above-ground N surplus was equal to or smaller than zero, yield-scaled N2O emissions remained stable and relatively small. At an N surplus of 90 kg N ha-1 yield-scaled emissions increased threefold. Furthermore, a negative relation between N use efficiency and yield-scaled N2O emissions was found. Therefore, we argue that agricultural management practices to reduce N2O emissions should focus on optimizing fertilizer-N use efficiency under median rates of N input, rather than on minimizing N application rates.
  • Authors:
    • Scholz, V.
    • Kern, J.
    • Strähle, M.
    • Hellebrand, H. J.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 87
  • Issue: 2
  • Year: 2010
  • Summary: Carbon (C) sequestration and soil emissions of nitrous oxide (N2O) affect the carbon dioxide (CO2) advantage of energy crops. A long-term study has been performed to evaluate the environmental effects of energy crop cultivation on the loamy sand soil of the drier northeast region of Germany. The experimental field, established in 1994, consisted of columns (0.25 ha each) cultivated with short rotation coppice (SRC: Salix and Populus) and columns cultivated with annual crops. The columns were subdivided into four blocks, with each receiving different fertilization treatments. The soil C content was measured annually from 1994 until 1997, and then in 2006. Soil N2O levels were measured several times per week from 1999 to 2007. Water-filled pore space (WFPS) and soil nitrate measurements have been performed weekly since 2003. Increased C stocks were found in SRC columns, and C loss was observed in blocks with annual crops. The soil from fertilized blocks had higher levels of C than the soil from non-fertilized blocks. SRC cropping systems on dry, loamy sand soils are advantageous relative to annual cropping systems because of higher C sequestration, lower fertilized-induced N2O emissions, and reduced background N2O emissions in these soils. SRC cropping systems on dry, loamy sand soils have a CO2 advantage (approximately 4 Mg CO2 ha(-1) year(-1)) relative to annual cropping systems.
  • Authors:
    • Andrasko, K.
    • Bosquet, B.
  • Year: 2010
  • Authors:
    • Schulze, E. D.
    • Houwelling, S.
    • Rivier, L.
    • Friedrich, R.
    • Scholz, Y.
    • Pregger, T.
    • Levin, I.
    • Piao, S. L.
    • Peylin, P.
    • Marland, G.
    • Paris, J. D.
    • Ciais, P.
  • Source: Global Change Biology
  • Volume: 16
  • Issue: 5
  • Year: 2010
  • Summary: We analyzed the magnitude, the trends and the uncertainties of fossil-fuel CO2 emissions in the European Union 25 member states (hereafter EU-25), based on emission inventories from energy-use statistics. The stability of emissions during the past decade at EU-25 scale masks decreasing trends in some regions, offset by increasing trends elsewhere. In the recent 4 years, the new Eastern EU-25 member states have experienced an increase in emissions, reversing after a decade-long decreasing trend. Mediterranean and Nordic countries have also experienced a strong acceleration in emissions. In Germany, France and United Kingdom, the stability of emissions is due to the decrease in the industry sector, offset by an increase in the transportation sector. When four different inventories models are compared, we show that the between-models uncertainty is as large as 19% of the mean for EU-25, and even bigger for individual countries. Accurate accounting for fossil CO2 emissions depends on a clear understanding of system boundaries, i.e. emitting activities included in the accounting. We found that the largest source of errors between inventories is the use of distinct systems boundaries (e.g. counting or not bunker fuels, cement manufacturing, non-energy products). Once these inconsistencies are corrected, the between-models uncertainty can be reduced down to 7% at EU-25 scale. The uncertainty of emissions at smaller spatial scales than the country scale was analyzed by comparing two emission maps based upon distinct economic and demographic activities. A number of spatial and temporal biases have been found among the two maps, indicating a significant increase in uncertainties when increasing the resolution at scales finer than ~200 km. At 100 km resolution, for example, the uncertainty of regional emissions is estimated to be 60 g C m-2 yr-1, up to 50% of the mean. The uncertainty on regional fossil-fuel CO2 fluxes to the atmosphere could be reduced by making accurate 14C measurements in atmospheric CO2, and by combining them with transport models.
  • Authors:
    • Hodgson, J.
    • Bogaard, A.
    • Charles, M.
    • Jones, G.
  • Source: Journal of Archaeological Science
  • Volume: 37
  • Issue: 1
  • Year: 2010
  • Summary: This paper brings together the results of five present-day studies of arable weed ecology, and applies these to the identification of past crop husbandry regimes on the basis of archaeobotanical weed assemblages. The contrasting husbandry regimes covered by the present-day studies include irrigation and dry farming, fallowing and rotation, intensive and extensive cultivation, and autumn and spring sowing. The weed floras associated with these regimes were analysed in terms of the functional ecology of the species represented. These same functional attributes, that distinguished contrasting regimes, were then measured for the weed species found accompanying crop seeds in two archaeobotanical studies, of the Islamic site of Khirbet Faris, S. Jordan and Neolithic sites in central Europe. Analyses using these functional measurements resulted in the identification of irrigation at the former and in the identification of sowing time and intensive cultivation at the latter.
  • Authors:
    • Varrelmann, M.
    • Buhre, C.
    • Kluth, C.
  • Source: Plant Pathology
  • Volume: 59
  • Issue: 4
  • Year: 2010
  • Summary: The susceptibility of intercrop species (Raphanus sativus, Brassica juncea, B. rapa, Sinapis alba and Phacelia tanacetifolia) to the sugar beet pathogen Rhizoctonia solani was investigated in vitro, in the greenhouse and in the field with artificial inoculation. Disease severity in subsequently cultivated sugar beet was monitored in the field. Differences in susceptibility between species were found to be consistent in all experimental systems. All intercrop species were susceptible to R. solani. Brassica rapa and R. sativus were less susceptible than P. tanacetifolia. Compared to fallow, the cultivation of B. rapa and R. sativus reduced disease severity in subsequently grown sugar beet (median ratings of up to 3.0 and 3.5, respectively, depending on environmental conditions). This resulted in higher white sugar yield compared to fallow (up to 210% and 157% for B. rapa and R. sativus, respectively). This study demonstrates that in vitro and greenhouse resistance tests are suitable systems to predict the effects of intercrop species susceptibility in the field on disease severity and white sugar yield in subsequently grown sugar beet. Intercrop breeding programmes might profit from fast and efficient screening tests to provide Rhizoctonia-resistant intercrops as an additional control measure against R. solani in sugar beet.