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  • 1
    Language: English
    In: Cold Regions Science and Technology
    Description: The compaction of arable soils caused by driving over them with agricultural machinery poses a serious problem in numerous agricultural regions across temperate climate zones. The risk of compaction is particularly high in early spring or late autumn when soils are wet. This is why driving over soils frozen near the surface is recommended in some cases in temperate climate zones to prevent soil compaction. However, no findings have been available about the thickness of frozen soil required to effectively prevent compaction when the soil is driven over. In one experiment, soil physical measurements were carried out on the topsoil after a single pass with a tractor (4100 kg wheel load, 80 kPa inflation pressure) over an unfrozen variant, a variant with 2–3 cm frost covering and a variant with 5–7 cm frost covering, with comparisons made with a control variant that had not been driven over. Driving over the unfrozen variant led to a significant compaction of the whole of the topsoil. By contrast, the frozen surfaces were able to significantly buffer the compaction. No appreciable differences were detected between the two depths of frost penetration. A depth of frost penetration of as little as 2–3 cm was therefore sufficient to reduce the risk of compaction with a wheel load of approximately 4000 kg and appropriately adjusted inflation pressure. Highlights ► We analyze the impact of a single pass with a tractor over an unfrozen soil. ► In addition were analyzed variants with 2–3 cm and 5–7 cm frost cover. ► All variants were compared with a control variant. ► Driving over the unfrozen variant led to a significant compaction of the topsoil. ► By contrast, the frozen surfaces were able to significantly buffer the compaction.
    Keywords: Frozen Soil ; Soil Compaction ; Tyre Sinkage
    ISSN: 0165-232X
    E-ISSN: 18727441
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  • 2
    Language: English
    In: Journal of Environmental Management, 1 October 2016, Vol.181, pp.54-63
    Description: Avoiding soil compaction caused by agricultural management is a key aim of sustainable land management, and the soil compaction risk should be considered when assessing the environmental impacts of land use systems. Therefore this project compares different crop rotations in terms of soil structure and the soil compaction risk. It is based on a field trial in Germany, in which the crop rotations (i) silage maize (SM) monoculture, (ii) catch crop mustard (Mu)_sugar beet (SB)-winter wheat (WW)-WW, (iii) Mu_SM-WW-WW and (iv) SB-WW-Mu_SM are established since 2010. Based on the cultivation dates, the operation specific soil compaction risks and the soil compaction risk of the entire crop rotations are modelled at two soil depths (20 and 35 cm). To this end, based on assumptions of the equipment currently used in practice by a model farm, two scenarios are modelled (100 and 50% hopper load for SB and WW harvest). In addition, after one complete rotation, in 2013 and in 2014, the physical soil parameters saturated hydraulic conductivity (kS) and air capacity (AC) were determined at soil depths 2–8, 12–18, 22–28 and 32–38 cm in order to quantify the soil structure. At both soil depths, the modelled soil compaction risks for the crop rotations including SB (Mu_SB-WW-WW, SB-WW-Mu_SM) are higher (20 cm: medium to very high risks; 35 cm: no to medium risks) than for those without SB (SM monoculture, Mu_SM-WW-WW; 20 cm: medium risks; 35 cm: no to low risks). This increased soil compaction risk is largely influenced by the SB harvest in years where soil water content is high. Halving the hopper load and adjusting the tyre inflation pressure reduces the soil compaction risk for the crop rotation as a whole. Under these conditions, there are no to low soil compaction risks for all variants in the subsoil (soil depth 35 cm). Soil structure is mainly influenced in the topsoil (2–8 cm) related to the cultivation of Mu as a catch crop and WW as a preceding crop. Concerning kS, Mu_SB-WW-WW (240 cm d−1) and Mu_SM-WW-WW (196 cm d−1) displayed significantly higher values than the SM monoculture (67 cm d−1), indicating better structural stability and infiltration capacity. At other soil depths, and for the parameter AC, there are no systematic differences in soil structure between the variants. Under the circumstances described, all crop rotations investigated are not associated with environmental impacts caused by soil compaction. •Soil compaction risk was modelled for entire crop rotations on farm scale.•Crop rotations with sugar beet and/or silage maize were tested for soil structure.•Crop rotations caused medium to very high risks for the topsoil.•Risks were low for the subsoil when reducing hopper load/tyre inflation pressure.•Differences in soil structure were not related to sugar beet or silage maize cropping.
    Keywords: Sugar Beet ; Silage Maize ; Air Capacity ; Saturated Hydraulic Conductivity ; Repro
    ISSN: 0301-4797
    E-ISSN: 10958630
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  • 3
    Language: English
    In: Industrial Crops & Products, April 2015, Vol.66, pp.206-209
    Description: •In all study trials both manures stimulate the earthworm population.•Earthworm density under digestate was similar to conventional slurry.•Applying digestate and slurry had a positive impact earthworm density and biomass.•Mineral fertilizers had negatively affected earthworm fauna.•Community composition was strongly influenced by the application of digestate. In recent years, the increasing number of biogas plants in operation has also led to a considerable rise in fermentative substrates, which are now widely used as agricultural fertilizers. The impact on earthworm fauna of using biogas digestate as a fertilizer has yet to be sufficiently researched. At two different tests sites, the short-term (four months after fertilization) and longer-term (three-year test period) influence of using fermented residues as a fertilizer was examined on earthworm density, biomass and community composition compared to using traditional fertilizers (cattle and pig slurry, chemical fertilizers as well as an unfertilized control). The crop grown was maize (Zea mays L.). Applying biogas digestate and slurry had a positive overall impact at both sites on earthworm density and biomass. Observing different fertilization regimes in the short term, the significantly highest earthworm density was seen where slurry had been applied. In the treatments with digestate and conventional slurry, earthworm biomass differed significantly in comparison with chemical fertilization and the untreated variant. After three years, earthworm biomass in the variants fertilized with conventional slurry and digestate tended to be higher than in the chemical fertilizer and untreated variants. Community composition was strongly influenced by the application of digestate. A decrease in the species Aporrectodearosea was accompanied by an increase in Aporrectodea caliginosa. The earthworm population was supported equally positively at both sites by the variants with conventional slurry and digestate.
    Keywords: Biogas Digestate ; Slurry ; Earthworms ; Community Composition ; Biogas Plants
    ISSN: 0926-6690
    E-ISSN: 1872633X
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  • 4
    Language: English
    In: Geoderma, May 2012, Vol.177-178, pp.1-7
    Description: Precompression stress is an important criterion in soil mechanics and is often determined at a water content equivalent to a matric potential of −6kPa. In German-speaking countries, this matric potential corresponds to field capacity. Yet in order to assess the risk of compaction in arable soils, it needs to be known for a wide range of soil water content levels. The site-specific determination of relationships between precompression stress and matric potential or water content is, however, highly labour intensive. Furthermore, previous regression models can only deduce changes in precompression stress depending on water content to a limited extent and not for all values. Alternatively, these models do not directly include precompression stress at a matric potential of −6kPa as the basis of calculation. Thus the derivation and validation of a simple model are to be presented, which can be used to predict any precompression stress for decreasing soil water content levels. This requires only an initial precompression stress for a matric potential of −6kPa and the respective soil water content as a percentage of field capacity. The model is based primarily on an analysis of numerous studies in which precompression stress was determined for various matric potentials. Relationships between precompression stress at a matric potential of −6kPa and the relative water content as a percentage of field capacity at a matric potential of −30kPa were also derived in the laboratory. These data were used to develop a mathematical model for four soil texture classes, as well as “All texture classes” collectively. This model was tested by way of soil compression tests and the determining of precompression stress at 25 sites. All soil compression tests were initially carried out with a matric potential of −6kPa. Tests were carried out in parallel to this with greater matric potentials (−10 to −1500kPa). The accuracy of the modelling approach presented here is good, both in terms of the use of systems of equations for “All texture classes” and for differentiated soil texture classes. In comparison to the regression model for all texture classes, calculation according to soil texture class causes a reduction of the mean absolute errors from 0.15 to 0.11 and of the RMSE from 0.19 to 0.14. Simultaneously, the coefficient of determination and the index of agreement (IA) increase, from 0.54 to 0.67 and 0.92 to 0.95 respectively. Calculation according to different soil texture classes is therefore particularly recommended in the case of applications with high accuracy requirements. Highlights► Derivation and validation of a simple model are to be presented. ► The model predicts precompression stress for decreasing soil water contents. ► This model requires only an initial precompression stress and water content. ► The accuracy of the modelling approach presented here is good.
    Keywords: Soil Water Content ; Precompression Stress ; Modelling Soil Compaction ; Soil Strength ; Soil Degradation
    ISSN: 0016-7061
    E-ISSN: 18726259
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  • 5
    Language: English
    In: Geoderma, 2013, Vol.209, pp.226-232
    Description: Many arable soils have significant horizon-specific gravel content levels. Just how these influence compaction behaviour, and in particular precompression stress as an important criterion of a soil's susceptibility to compaction, has yet to be sufficiently clarified. This article is intended to contribute towards answering this question. Firstly, three different fine earths, from the “Clay”, “Silt Loam” and “Sandy Loam” soil texture classes were mixed with staggered proportions (0, 10, 20, 30, 40% by volume) of a quartz gravel (the shape of which was subrounded to rounded, average weighted diameter 6mm). Soil core samplers were filled with the mixtures at a typical density for a natural site. In the case of the 30% by volume variant only, in addition to the quartz gravel an angular to subangular limestone gravel with the same size graduation was also used. The tests were supplemented by 20 samples from a natural site; the gravel content of these varied between 0.1 and 23.5% by volume. All of the disturbed and natural samples were adjusted to a water content at a matric potential of −6kPa. Subsequently, an oedometer test was used to apply loads to them in stages (5–550kPa). Precompression stress was calculated using the resulting stress–bulk density functions. While fine earth bulk density remained constant, the staggered addition of quartz gravel led to an increase in the whole soil density after packing, and thus also to a vertical shift in overall stress–bulk density functions. However, the stress–density functions of the fine earth do show that the overall compaction of fine earth decreased as gravel content increased. In the case of low gravel content levels of no more than 10% by volume, the increase in precompression stress (log) in the disturbed samples was, on the whole, very low. In the disturbed samples, however, as gravel content increased precompression stress (log) increased exponentially. Contrary to this, a continuous linear increase in precompression stress (log) could be observed with increasing gravel content in the natural samples. The angular to subangular shape of the gravel only resulted in greater precompression stress (log) in the “Silt Loam”. At gravel-rich sites, gravel content influences soil compaction behaviour and precompression stress very strongly. For this reason, it is essential that it be considered when assessing such sites' risk of compaction damage. ; p. 226-232.
    Keywords: Clay ; Limestone ; Bulk Density ; Core Samplers ; Soil Compaction ; Silt ; Gravel ; Soil Density ; Risk ; Soil Texture ; Quartz ; Water Content ; Arable Soils
    ISSN: 0016-7061
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 6
    Language: English
    In: Geoderma, November 2013, Vol.209-210, pp.226-232
    Description: Many arable soils have significant horizon-specific gravel content levels. Just how these influence compaction behaviour, and in particular precompression stress as an important criterion of a soil's susceptibility to compaction, has yet to be sufficiently clarified. This article is intended to contribute towards answering this question.Firstly, three different fine earths, from the “Clay”, “Silt Loam” and “Sandy Loam” soil texture classes were mixed with staggered proportions (0, 10, 20, 30, 40% by volume) of a quartz gravel (the shape of which was subrounded to rounded, average weighted diameter 6mm). Soil core samplers were filled with the mixtures at a typical density for a natural site. In the case of the 30% by volume variant only, in addition to the quartz gravel an angular to subangular limestone gravel with the same size graduation was also used. The tests were supplemented by 20 samples from a natural site; the gravel content of these varied between 0.1 and 23.5% by volume. All of the disturbed and natural samples were adjusted to a water content at a matric potential of −6kPa. Subsequently, an oedometer test was used to apply loads to them in stages (5–550kPa). Precompression stress was calculated using the resulting stress–bulk density functions.While fine earth bulk density remained constant, the staggered addition of quartz gravel led to an increase in the whole soil density after packing, and thus also to a vertical shift in overall stress–bulk density functions. However, the stress–density functions of the fine earth do show that the overall compaction of fine earth decreased as gravel content increased. In the case of low gravel content levels of no more than 10% by volume, the increase in precompression stress (log) in the disturbed samples was, on the whole, very low. In the disturbed samples, however, as gravel content increased precompression stress (log) increased exponentially. Contrary to this, a continuous linear increase in precompression stress (log) could be observed with increasing gravel content in the natural samples. The angular to subangular shape of the gravel only resulted in greater precompression stress (log) in the “Silt Loam”.At gravel-rich sites, gravel content influences soil compaction behaviour and precompression stress very strongly. For this reason, it is essential that it be considered when assessing such sites' risk of compaction damage. •The impact of gravel content and shape on mechanical soil properties was examined.•Fine earth in gravelly soils is less susceptible to compaction.•As gravel content rises, the change in pre-compression stress (log) depends on the texture and bulk density of the fine earth.•Gravel shape had no clear effect on precompression stress (log).
    Keywords: Gravel Content ; Gravel Shape ; Precompression Stress ; Soil Compaction ; Dry Bulk Density ; Fine Earth Bulk Density
    ISSN: 0016-7061
    E-ISSN: 18726259
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  • 7
    Language: English
    In: European Journal of Agronomy, January 2017, Vol.82, pp.50-59
    Description: •Yield increases with increasing cropping interval for sugar beet.•Yield and yield stability are lowest when sugar beet is cultivated as a preceding crop.•Cropping interval of two years seems necessary for high yield stability.•Integrating alfalfa enables shorter cropping intervals without yield loss. Long-term field trials constitute an essential basis for research into the effects of agricultural management practices on yield and soil properties. The long-term field trial Etzdorf (Germany) was set up in 1970 and uses various crop rotations with sugar beets (Beta vulgaris L., SB) to investigate the influence of increasing cropping concentrations (20 %–100 %) and decreasing cropping intervals (0–4 years) on the yield and quality parameters of SB. However, evaluation of the yield stability of SB in diverse crop rotations has not been conducted in this context so far. For this reason, the yield for the last 13 years of the trial (2002 until 2014) was subjected to such an evaluation. Besides cropping interval and cropping concentration, the crop rotations investigated also differed in terms of the complementary crops cultivated (winter wheat, Triticum aestivum L.; alfalfa, Medicago ssp.; potato, Solanum tuberosum L. and grain maize, Zea mays L.). Both SB root yield and white sugar yield increased with an increasing cropping interval or decreasing cropping concentration of SB in the crop rotation. In addition, a positive effect on root yield and white sugar yield was seen when integrating alfalfa, while cultivating SB after SB displayed the lowest root yield and white sugar yield. Sugar content was lowest in SB monoculture. In order to assess stability of white sugar yield, the coefficient of variation and ecovalence were calculated, and a linear regression analysis of the individual crop rotations’ annual yield was performed for the annual average of all crop rotations. When considering these three parameters, the crop rotations with a cropping interval of at least 2 years displayed higher yield stability, with simultaneously higher white sugar yield, than the crop rotations with a cropping interval of 0 and 1year. By integrating alfalfa into the crop rotation, it was also possible to achieve above-average white sugar yield with high yield stability for a cropping interval of 1year.
    Keywords: Ecovalence ; Linear Regression Analysis ; Coefficient of Variation ; Cropping Interval
    ISSN: 1161-0301
    E-ISSN: 18737331
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  • 8
    Language: English
    In: Soil & Tillage Research, January 2018, Vol.175, pp.205-216
    Description: •Strip tillage created two locally different soil structures.•Strip tillage led to both high bulk density and saturated conductivity between seed rows.•Macroporosity and pore connectivity were higher in tilled than in untilled treatments.•Under strip tillage, precompression stress was higher between than within seed rows. In recent years, there has been an increased application of conservation-oriented tillage techniques, where instead of being turned the soil is only loosened or not tilled at all. Strip tillage, a special form of conservation tillage, results in small-scale structural differences, since tillage is performed only within the seed row, while the soil between seed rows is not tilled. However, tillage always impacts upon physical soil properties and processes.A combined application of conventional soil mechanical methods and X-ray computed tomography (X-ray CT) is employed here in order to investigate small-scale structural differences in a chernozem (texture 0–30 cm: silt loam) located in central Germany under strip tillage (within and between seed rows) compared to no tillage and mulch tillage. Apart from recording changes over time (years: 2012, 2014, 2015) to dry bulk density and saturated conductivity at soil depths 2–8 and 12–18 cm, stress-strain tests were conducted to map mechanical behaviour for a load range of 5–550kPa at a soil depth of 12–18cm (year 2015). Mechanical precompression stress was determined from the stress-dry bulk density curves. In addition, computed tomography scans were created followed by quantitative image analysis of the morphometric parameters mean macropore diameter, macroporosity, connectivity and anisotropy of the same soil samples.For strip tillage between seed rows and no tillage, a significant increase in dry bulk density was observed over time compared to strip tillage within the seed row and mulch tillage. This was more pronounced at a soil depth of 2–8cm than at 12–18cm. Despite higher dry bulk density, strip tillage between the seed row displayed also an increasing saturated conductivity compared to strip tillage within the seed row and mulch tillage. The computed tomography scans showed that the macropores became more compressed and soil aggregates were pushed together as mechanical stress increased, with the aggregate arrangement being transformed down into a coherent soil mass. The soil mechanical and morphometric parameters supported each other in terms of what they revealed about the mechanical properties of the soil structures. For instance, in the strip tillage between seed rows and no tillage treatments, the lack of soil tillage not only resulted in higher dry bulk densities, but also higher aggregate densities, mechanical precompression stress values, mean macropore diameters as well as lower macroporosity and connectivity values compared to mulch tillage and strip tillage within the seed row. The computed tomography parameters are therefore highly suitable for providing Supplementary information about the compaction process. Overall, this study showed that strip tillage combines the advantages of no tillage and a deeper, soil conservation-oriented primary tillage because, on a small scale, it creates two distinct soil structures which are beneficial in terms of optimal plant growth as well as mechanical resistance by driving over the soil.
    Keywords: Pre-Compression Stress ; Dry Bulk Density ; Aggregate Density ; Image Analysis ; Soil Compaction
    ISSN: 0167-1987
    E-ISSN: 18793444
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  • 9
    Language: English
    In: Applied Energy, 15 March 2017, Vol.190, pp.114-121
    Description: •GHG-emission, bioenergy yield, GHG-saving potential based on field trial data.•Results complement the absence of default values, especially for sugar beet.•Results represent Central European conditions of crop and biogas production. The study delivers values on greenhouse gas (GHG)-emission via cultivation of silage maize and sugar beet and of GHG-saving potential of electricity produced from biogas out of both biomass crops. Data are based on three rainfed crop rotation field trials in Germany (2011–2014) representative for Central Europe and can serve as default values. It was found that GHG-emission via crop cultivation was driven mainly by nitrous oxide emission from soil and mineral N-fertilizer use and was 2575–3390kg carbon dioxide equivalents (CO2eq) per hectare for silage maize and 2551–2852kgCO2eqha−1 for sugar beet (without biogas digestate application). Integrating a GHG-credit for surplus N in the biogas digestate reduced total GHG-emission via crop cultivation to 65–69% for silage maize but only to 84–97% for sugar beet. The GHG-saving potential of electricity production from biogas was calculated for three biogas plants differing in technical characteristics. The GHG-saving potentials were generally 〉70% (silage maize: 78–80%, sugar beet: 72–76%) and the authors concluded that the technical setting of the biogas plant had a slight impact only. Overall, the authors assumed that the major potential for GHG-emission's reduction along the bioenergy production chain were N-management during crop cultivation and methane losses at the biogas plant. Finally, sugar beet, if cultivated in crop rotation, was shown to be an efficient alternative to silage maize as a biomass crop in order to achieve a higher diversity in biomass crop cultivation.
    Keywords: Combined Heat Power ; Cultivation ; Digestate ; Methane ; Germany
    ISSN: 0306-2619
    E-ISSN: 18729118
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  • 10
    Language: English
    In: Field Crops Research, September 2016, Vol.196, pp.75-84
    Description: •Empirical data on biomass crop production in three field trials in Central Europe.•Entire crop rotations evaluated for net-energy yield, energy efficiency, land demand.•Energy input and output on field scale.•Data for sugar beet as biomass crop. Empirical data on energy performance (net-energy yield, energy efficiency, land demand) of biomass crop cultivation are needed for policy and agronomic decision making. Energy input and energy performance of the cultivation of silage maize (SM), sugar beet (SB), and winter wheat (WW) in crop rotations and continuous cultivation were evaluated on the basis of three field experiments on highly productive sites in Germany. Silage maize and SB root were considered as crops for biogas production and WW as a food crop. Even if SM cultivation needed the largest energy input across sites and years (19–22GJha−1a−1), the energy output compensated for it and largest net-energy yield (212–317GJha−1a−1), energy efficiency (11.4–17.1GJGJ−1), and smallest land demand (33–48m2GJ−1) were observed. For SB cultivation, energy input (15–19GJha−1a−1) and energy performance were lower (119–266GJha−1a−1, 9.1–14.7GJGJ−1, 38–279m2GJ−1, respectively). Differences between both crops were significant (p≤0.05), but not in all cases. Winter wheat cultivation required an energy input of 13–18GJha−1a−1 and showed the lowest energy performance (103–119GJha−1a−1, 6.6–8.6GJGJ−1, 84–102m2GJ−1, respectively). The net-energy yield and land demand values presented are among the largest and the lowest, respectively, for rainfed Central European conditions. As the preceding crops, SB induced a higher energy performance of the subsequent WW than SM. When taking such crop rotation effects into account for the overall evaluation, we concluded that SB root as a biomass crop is a suitable alternative to SM.
    Keywords: K 2 O ; Mgo ; Mu ; P 2 O 5 ; SB ; SM ; Ww ; Bioenergy ; Biomass ; Energy Input ; Net-Energy Yield ; Winter Wheat ; Central Europe
    ISSN: 0378-4290
    E-ISSN: 18726852
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