The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Wulf Amelung - One of the best experts on this subject based on the ideXlab platform.
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Subsoil phosphorus is affected by fertilization regime in long term agricultural experimental trials
European Journal of Soil Science, 2018Co-Authors: Sara L Bauke, C Von Sperber, Federica Tamburini, Martina Gocke, Bernd Honermeier, Kathlin Schweitzer, Michael Baumecker, A Sandhagehofmann, Wulf AmelungAbstract:Arable Subsoils store large amounts of phosphorus (P); however, it is unclear to what extent, and under which conditions, Subsoil resources might supplement crop P acquisition. Here, we hypothesized that (i) insufficient supply of P in topsoil promotes P acquisition from Subsoil and (ii) Subsoil P cycling is regulated by nitrogen (N) supply. We sampled two German long-term fertilizer trials in Thyrow (sandy soil) and Giesen (loamy-clayey soil) to 100-cm depth. Treatments received either NPK, NK or PK fertilizer for > 60 years. We assessed soil inorganic (Pi) and organic (Po) P pools following Hedley sequential extraction, and the oxygen isotopic composition of HCl-extractable phosphate (~d18OHCl-P), which differentiates P from primary and secondary (previously biologically cycled)minerals.We found that in theHedley sequential extraction Subsoil resin-P stocks (30–100 cm) in NK plots were 60% (Thyrow) and 8% (Giesen) less than those in NPK plots. Subsoil HCl Pi stocks in NK exceeded those of NPK plots by 70% in Thyrow, but not in Giesen. The NK treatments showed significantly smaller Subsoil ~d18OHCl-P values than NPK treatments, indicating a predominance of primary (not biologically cycled) minerals and refuting our hypothesis that P deficiency promotes P acquisition from primary minerals. Under N-limiting conditions, Subsoil resin-P stocks exceeded those under NPK fertilizer by 117% (Thyrow) and 22% (Giesen), supporting our second hypothesis. We conclude that an efficient use of Subsoil P resources is achieved only when nutrient supply in arable topsoils is sufficient.
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Biopore effects on phosphorus biogeochemistry in Subsoils
Soil Biology & Biochemistry, 2017Co-Authors: Sara L Bauke, C Von Sperber, Federica Tamburini, Nina Siebers, Wulf AmelungAbstract:Abstract Biopores are characterised by high concentrations of plant available nutrients and provide preferential pathways for root growth into the Subsoil, thereby potentially enabling plants to access phosphorus (P) resources located in the Subsoil. Here, we sampled biopores from a replicated agricultural field trial in Klein-Altendorf, Germany, to analyse their nutrient composition and P speciation as determined by Hedley sequential extraction and X-ray absorption near edge structure (XANES) spectroscopy. In addition, we analysed the oxygen isotopic composition of HCl P (δ18OHCl P) as an indicator of long-term effects of biological P turnover. We found that biopore effects were most pronounced in the Subsoil, where the concentration of easily extractable (labile) P tended to be greater in biopores than in bulk soil, as evident in both Hedley sequential extraction and XANES spectroscopy. We assume that these findings result from inputs of organic matter from the topsoil as well as an input of Ca-particles into Subsoil biopores by earthworm activity. Biologically cycled P was subsequently precipitated as Ca-P as evident by δ18OHCl P values close to equilibrium in biopores even at great depths. When incubating bulk soil samples with 18O-labelled water, however, we observed a significant increase of δ18OHCl P values in the topsoil, but only small if any changes of δ18OHCl P values in the Subsoil. Thus, biopores present hotspots of P cycling in the Subsoil, but the effect of biopores on overall P turnover in the bulk Subsoil is limited.
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phosphorus fractions in bulk Subsoil and its biopore systems
European Journal of Soil Science, 2014Co-Authors: J A M Barej, Stefan Patzold, Ute Perkons, Wulf AmelungAbstract:Summary Improving phosphorus (P) accessibility in Subsoils could be a key factor for sustainable crop management. This study aims to explain the quantity of different P fractions in Subsoil and its biopore systems, and to test the hypothesis that crops with either fibrous (fescue) or tap-root systems (lucerne and chicory) leave behind a characteristic P pattern in bulk Subsoil, biopore linings and the rhizosphere. The crops were cultivated for up to 3 years in a randomized field experiment on a Haplic Luvisol developed from loess. Aqua regia-extractable P (referred to as total P) and calcium acetate lactate-extractable P (PCAL) were assessed at 0–30 (Ap horizon), 30–45 (E/B horizon), 45–75 and 75–105 cm Subsoil depths. In addition, sequential P fractionation was performed on different soil compartments between 45 and 75 cm depths. The results showed that total P stocks below the Ap horizon (30–105 cm) amounted to 5.6 t ha−1, which was twice as large as in the Ap, although the Ap contained larger portions of PCAL. Both PCAL and sequential P extractions showed that biopore linings and the rhizosphere at the 45–75 cm depth were enriched, rather than depleted, in P. The content of inorganic P (81–90% of total P) increased in the following order: bulk soil = biopores 2 mm. Biopores >2 mm and rhizosphere soil were clearly enriched in resin- and NaHCO3-extractable Pi and Po fractions. However, we failed to attribute these P distribution patterns to different crops, suggesting that major properties of biopore P originated from relict biopores, rather than being influenced by recent root systems. The stocks of the sum of these P fractions in the bulk Subsoil (182 kg ha−1 at 45–75 cm depth) far exceeded those in the biopores (3.7 kg ha−1 in biopores >2 mm and 0.2 kg ha−1 in biopores <2 mm). Hence, these biopores may form attractive locations for root growth into the Subsoil but are unlikely to sustain overall plant nutrition.
P Weisskopf - One of the best experts on this subject based on the ideXlab platform.
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Subsoil compaction risk avoidance identification and alleviation
Soil & Tillage Research, 2003Co-Authors: G Spoor, F G J Tijink, P WeisskopfAbstract:This paper aims to provide guidance for field practitioners on the vulnerability of different Subsoils to compaction under different field conditions and on the tyre pressures necessary to reduce or avoid damage. It also indicates ways of identifying situations where some compaction alleviation may be necessary to improve Subsoil conditions and methods for alleviating Subsoil compaction problems, without increasing the risk of more extensive compaction damage in the future.
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prevention strategies for field traffic induced Subsoil compaction a review part 2 equipment and field practices
Soil & Tillage Research, 2003Co-Authors: Tim Chamen, Laura Alakukku, Sandra Pires, C Sommer, Gordon Spoor, Frans Tijink, P WeisskopfAbstract:The loads imposed by modern farm machinery have considerable potential to increase Subsoil stress. Within the context of economically viable and environmentally sustainable systems, the practices associated with Subsoil damage and methods for avoidance are identified. The greatest potential for damage is on fragile, wet or loosened Subsoils combined with high wheel or track loads and contact pressures that create noticeable ruts in the topsoil. In-furrow ploughing increases this potential considerably by placing loads on the Subsoil. Measures to avoid this potential involve a whole farm approach and an understanding of the many interactions between cropping systems and machinery. Alternatives to in-furrow ploughing that involve working from the surface and building a protective topsoil are discussed. Key measures to reduce the risk to Subsoils involve a clear understanding of tyre load and inflation data and simple on-farm methods of achieving this are suggested. Although avoidance has the potential to reduce the risk, confinement of damage to specific strips in the field is seen as a realistic alternative. Controlled traffic operations, together with precision guidance, offer an economic means by which compaction on the cropped area can be avoided. The most effective route to improvement in soil care across the European Union (EU) is an appropriate management structure coupled with a best practice framework.
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prevention strategies for field traffic induced Subsoil compaction a review part 1 machine soil interactions
Soil & Tillage Research, 2003Co-Authors: Laura Alakukku, F G J Tijink, P Weisskopf, Sandra Pires, C Sommer, W C T Chamen, J P Van Der Linden, G SpoorAbstract:Subsoil compaction is a severe problem mainly because its effects have been found to be long-lasting and difficult to correct. It is better to avoid Subsoil compaction than to rely on alleviating the compacted structure afterwards. Before recommendations to avoid Subsoil compaction can be given, the key variables and processes involved in the machinery–Subsoil system must be known and understood. Field traffic-induced Subsoil compaction is discussed to determine the variables important to the prevention of the compaction capability of running gear. Likewise, technical choices to minimise the risk of Subsoil compaction are reviewed. According to analytical solutions and experimental results the stress in the soil under a loaded wheel decreases with depth. The risk of Subsoil compaction is high when the exerted stresses are higher than the bearing capacity of the Subsoil. Soil wetness decreases the bearing capacity of soil. The most serious sources of Subsoil compaction are ploughing in the furrow and heavy wheel loads applied at high pressure in soft conditions. To prevent (sub)soil compaction, the machines and equipment used on the field in critical conditions should be adjusted to actual strength of the Subsoil by controlling wheel/track loads and using low tyre inflation pressures. Recommendations based on quantitative guidelines for machine/soil interactions should be available for different wheel load/ground pressure combinations and soil conditions. © 2003 Elsevier Science B.V. All rights reserved.
Mirjam Helfrich - One of the best experts on this subject based on the ideXlab platform.
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Fate and stability of dissolved organic carbon in topsoils and Subsoils under beech forests
Biogeochemistry, 2020Co-Authors: Fabian Kalks, Patrick Wordell-dietrich, Patrick Liebmann, Georg Guggenberger, Karsten Kalbitz, Robert Mikutta, Mirjam HelfrichAbstract:Dissolved organic carbon (DOC) from Oa horizons has been proposed to be an important contributor for Subsoil organic carbon stocks. We investigated the fate of DOC by directly injecting a DOC solution from ^13C labelled litter into three soil depths at beech forest sites. Fate of injected DOC was quantified with deep drilling soil cores down to 2 m depth, 3 and 17 months after the injection. 27 ± 26% of the injected DOC was retained after 3 months and 17 ± 22% after 17 months. Retained DOC was to 70% found in the first 10 cm below the injection depth and on average higher in the topsoil than in the Subsoil. After 17 months DOC in the topsoil was largely lost (− 19%) while DOC in the Subsoil did not change much (− 4.4%). Data indicated a high stabilisation of injected DOC in the Subsoils with no differences between the sites. Potential mineralisation as revealed by incubation experiments however, was not different between DOC injected in topsoil or Subsoils underlining the importance of environmental factors in the Subsoil for DOC stabilisation compared to topsoil. We conclude that stability of DOC in Subsoil is primary driven by its spatial inaccessibility for microorganisms after matrix flow while site specific properties did not significantly affect stabilisation. Instead, a more fine-textured site promotes the vertical transport of DOC due to a higher abundance of preferential flow paths.
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factors controlling the variability of organic matter in the top and Subsoil of a sandy dystric cambisol under beech forest
Geoderma, 2018Co-Authors: Stefanie Heinze, Mirjam Helfrich, Robert Mikutta, Bernard Ludwig, Hanspeter Piepho, Patrick Wordelldietrich, Dietrich Hertel, Christoph Leuschner, Kristina Kirfel, Ellen KandelerAbstract:Abstract Organic carbon in Subsoils amounts to 40–60% of the global soil carbon pool and is generally characterized by apparent turnover times of hundreds to thousands of years and an increasing spatial variability with depth. The objective of this study was to analyze the amounts and distribution of SOC and to elucidate the turnover and storage mechanisms throughout deep soil profiles of a sandy Dystric Cambisol on Pleistocene glacial deposits under beech forest in northern Germany. The soil was sampled within a grid design at three replicated profiles, each at 8 sampling depths (10, 35, 60, 85, 110, 135, 160, 185 cm) and 8 horizontal sampling points. 192 samples were analyzed for bulk density, texture, pH, SOC, total N, 13 C-SOC, oxalate- and dithionite-extractable Fe and Al, root bio- and necromass, and microbial biomass C. For each sampling depth, a multi-effect model analysis was performed to identify the parameters explaining SOC variability. While SOC in the topsoil is only related to pH and dithionite-extractable Al, SOC in the Subsoil is always related to root bio- and necromass and to Fe oxides and/or silt content. The comparison of SOC within rooted and root-free Subsoil samples showed an up to 10 times higher SOC content in the rooted soil samples in comparison to the root-free samples. While the SOC content in the root-free soil declined with increasing depth the rooted soil samples showed no stratification with depth but were characterized by a higher spatial variability of SOC. At the same time, SOC in rooted soil samples has the same δ 13 C values as in root-free samples, indicating a similar degree of microbial processing. Microbial biomass C (C mic ) was not different between rooted and root-free samples, resulting in much higher C mic :SOC ratios in the root-free soil. Since rooted soil samples are characterized by significantly higher silt and oxalate-extractable Fe (Fe o ) contents, it appears that roots preferentially grow into these chemically and physically slightly more favorable zones. At the same time, these higher inputs were apparently better stabilized through sorption to silt and metal oxyhydroxides, thus leading to the longer-term SOC sequestration in these hot-spots enhancing the spatial variability of SOC in Subsoils.
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Controlling factors for the stability of Subsoil carbon in a Dystric Cambisol
Geoderma, 2017Co-Authors: Patrick Wordell-dietrich, Mirjam HelfrichAbstract:Abstract Subsoils store > 50 % of the total global soil organic carbon (SOC), and low SOC content and high mean residence times indicate that Subsoils have the potential to sequester additional C on the long-term. Nevertheless, the mechanisms controlling the turnover of SOC in Subsoils are poorly understood. The aim of this study was to assess the impact of temperature and substrate limitation on Subsoil SOC turnover and evaluate the stability of additional C inputs in Subsoils. In a 63-day microcosm incubation experiment, CO2 production of undisturbed soil samples from topsoil and two Subsoil depth increments was measured at two different temperatures (10 °C and 20 °C). Additionally, 13C labeled root litter was added to the different samples and measurements of the isotopic signature of the respired CO2 allowed a differentiation between SOC mineralization and root mineralization. The CO2 production per unit soil mass was lower in deep Subsoil than in the topsoil, but the CO2 production per unit SOC (specific mineralization) was three times higher in the deepest Subsoil than in topsoil. This depth gradient of specific mineralization in undisturbed samples indicates that deep Subsoil contained relatively more labile SOC than the topsoil. The temperature sensitivity of SOC mineralization expressed as Q10-q, decreased from around 3 to around 1 with increasing soil depth. In contrast, the mineralization of the added root material was solely determined by the recalcitrance of the added roots as indicated by a similar Q10-q through all three soil depths. Contrary to the SOC mineralization of undisturbed samples, significantly more added root litter was mineralized in the samples from the upper horizons than in the deepest Subsoil samples, revealing a non-linear relationship between mineralization of added C and the SOC content. Thus, the distance between substrate units, as indicated by the SOC content, may be key factor for Subsoil SOC dynamics. Moreover, root addition caused no positive priming effects in Subsoil horizons indicating that enhanced C inputs to the Subsoil can increase the SOC content and tap the unused C storage potential of Subsoils.
J J H Van Den Akker - One of the best experts on this subject based on the ideXlab platform.
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Subsoil Compaction and Ways to Prevent It
Managing soil quality: challenges in modern agriculture, 2020Co-Authors: J J H Van Den Akker, Per SchjønningAbstract:Subsoil compaction affects all aspects of soil quality, and contrary to topsoil compaction it is persistent. Natural alleviation processes such as wetting/drying, freezing/thawing and biological activity including root growth decrease rapidly with depth. In compacted soil, these alleviation processes are moreover diminished because root growth and biological activity are reduced and soil water contents remain higher in compacted than in well-structured soil. Wheel loads are still increasing and, in consequence, the extent and severity of Subsoil compaction. Sustainable soil management requires the uncompromising criterion that no Subsoil compaction can be accepted. Consequently, only field traffic with wheel loads lower than the carrying capacity of the Subsoil is allowed. This implies that Subsoil stress caused by wheel load should not exceed the strength of the Subsoil. Therefore, this chapter emphasises the importance of soil strength and the calculation of soil stresses in the Subsoil. One of the main constraints in using the carrying capacity concept proves to be the lack of data on soil strength. Existing recommended limits for wheel loads and inflation pressures are not adequate and can result in over or underestimating of allowable wheel loads and subsequent uneconomical solutions or Subsoil compaction. Adequate drainage of soils is a prerequisite for reduced Subsoil compaction. Mouldboard ploughing with all tractor wheels on the non-ploughed ‘land’ and umbilical systems for applying manure slurry are realistic options to reduce compaction. Controlled traffic systems that limit the wheeled area may be implemented by the use of wide span vehicles and by steering tractors along traffic lanes. Although we support such provisions, our chapter will advocate and focus primarily on adjusting wheel loads to the carrying capacity of the Subsoils.
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Two European concerted actions on Subsoil compaction
2020Co-Authors: J J H Van Den Akker, A. CanaracheAbstract:Subsoil compaction has been acknowledged by the European Union as a serious form of soil degradation and therefore EU finances two concerted actions on Subsoil compaction, scheduled for a duration between 1998 and 2001. The two CAs involve 49 institutes in 14 EU-member-countries, Switzerland, Norway, and 11 countries in Central and Eastern Europe. The general objective is to make an inventory of existing knowledge and experience with the distribution and impact of Subsoil compaction in Europe, to formulate recommended analytical and field experiments methods, to develop ways and guidelines to prevent Subsoil compaction, to identify gaps in knowledge and need for future research. The two concerted actions collaborate in the construction of two databases on literature, on soil mechanical properties and impact of Subsoil compaction on soil nutrients, soil physical properties, crop production and environment. Results
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socomo a soil compaction model to calculate soil stresses and the Subsoil carrying capacity
Soil & Tillage Research, 2004Co-Authors: J J H Van Den AkkerAbstract:Intensification of crop rotation and increasing use of machinery with high wheel loads are clearly related to compaction of the Subsoil. Subsoil compaction is persistent and the effect of natural and artificial loosening has been disappointing. Therefore, prevention of Subsoil compaction is the best way to preserve the structure and quality of the Subsoil. In addition to field studies, there is an increasing need for analytical tools to develop and evaluate measures for preventing Subsoil compaction. The objective of the research was to develop such a tool in the form of a computer model suitable for educators and extension workers, professional advisers, agricultural engineers and scientists. The analytical soil compaction model (SOCOMO) was developed to calculate soil stresses under wheel loads. In specific cases, the calculated stresses are compared with soil strengths measured in the laboratory. The calculated stresses were compared with known soil strengths or soil strengths determined with the help of pedotransfer functions. Subsoil compaction and deformation are prevented if the stresses exerted remain smaller than the actual strength of the Subsoil. To test the model, traffic experiments were performed and methods developed to measure stress, compaction and deformation in the Subsoil caused by wheel load. The test was successful and the model has been used to compare stresses under normal and low-pressure tires, as well as under tandem and dual-wheel configurations. SOCOMO was also used to construct a wheel-load carrying-capacity map of The Netherlands. The model is easy to use and requires only minimal input. However, it is not yet as user-friendly as it could be. Weak points of the model are that the rut depth must be estimated and that the shape of the pressure distribution exerted by the tire on the bottom of the rut is based on rules of thumb. The use of the concept that Subsoil compaction can be prevented by keeping the exerted stresses on the Subsoil below actual strength is frustrated by the fact that data and pedotransfer functions of soil strength are scarce. More measurements and development of pedotransfer functions are required.
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introduction to the special issue on experiences with the impact and prevention of Subsoil compaction in the european union
Soil & Tillage Research, 2003Co-Authors: J J H Van Den Akker, Johan Arvidsson, Rainer HornAbstract:Abstract The papers in this special issue present results of the European Union (EU) concerted action “Experiences with the impact of Subsoil compaction on soil crop growth and environment and ways to prevent Subsoil compaction”. The results and conclusions of earlier research on Subsoil compaction are memorized and it is emphasized that the conclusions are still sound: high axle load traffic on soils of high moisture content causes deep and persistent Subsoil compaction. The concerted action on Subsoil compaction in the EU and an almost identical concerted action on Subsoil compaction in central and eastern Europe are briefly introduced. This special issue presents a selection of papers of the concluding workshop of the concerted action on Subsoil compaction in the EU. It includes three papers on modeling the impact of Subsoil compaction on crop growth, water availability to plants and environmental aspects; three papers on modeling of Subsoil compaction by heavy machinery; four papers on measurement of soil mechanical and physical properties in relation to Subsoil compaction and four papers on methods to determine the risk of Subsoil compaction and to identify prevention strategies. The trends in agriculture in relation to Subsoil compaction are discussed. A positive trend is that policy makers in the EU and worldwide recognize soil as a vital and largely non-renewable resource increasingly under pressure. A negative trend is that wheel loads in agriculture are still increasing causing severe damage to Subsoils. The conclusion is that European Subsoils are more threatened than ever in history. Manufactures, agricultural engineers and soil scientists should collaborate and research should be initiated to solve this problem and find solutions. Subsoil compaction should be made recognized by all people involved from farmer to policy maker. Therefore an assessment of the existence and seriousness of Subsoil compaction throughout Europe should be initiated.
Klaus Lorenz - One of the best experts on this subject based on the ideXlab platform.
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the depth distribution of soil organic carbon in relation to land use and management and the potential of carbon sequestration in Subsoil horizons
Advances in Agronomy, 2005Co-Authors: Klaus LorenzAbstract:Routine soil surveys for estimating the soil organic carbon (SOC) pool account for a soil depth of about 1 m. Deeper soil horizons, however, may have a high capacity to sequester significant amounts of SOC as the turnover time and chemical recalcitrance of soil organic matter (SOM) increases with depth. The Subsoil carbon (C) sequestration may be achieved by higher inputs of fairly stable organic matter to deeper soil horizons. This can be achieved directly by selecting plants/cultivars with deeper and thicker root systems that are high in chemical recalcitrant compounds like suberin. Furthermore, recalcitrant compounds could be a target for plant breeding/biotechnology to promote C sequestration. A high surface input of organic matter favors the production of dissolved organic carbon that can be transported to deeper soil horizons and thus contribute to the Subsoil C storage. By promoting the activity of the soil fauna, organic matter can be transferred to deeper soil layers and stabilized (e.g., in earthworm casts). Manipulating the Subsoil microorganisms may result in higher amounts of fairly stable aliphatic compounds. The Subsoil below 1‐m depth may have the potential to sequester between 760 and 1520 Pg C. These estimates are, however, highly uncertain and more studies on C storage in Subsoil horizons and the assessment of the chemical nature of Subsoil organic C are needed.
