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| Registros recuperados: 16 | |
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| Christensen, B.T.. |
| Physical fractionation is used increasingly to study the turnover of organic matter in soil. This essay links the methods of fractionation to concepts of turnover by defining levels of structural and functional complexity that refer to experimentally verifiable pools of organic matter in the soil. Physical fractionation according to size and density of soil particles emphasizes the importance of interactions between organic and inorganic soil components in the turnover of organic matter. It allows the separation of free and occluded uncomplexed organic matter and of primary and secondary organomineral complexes. This methodological approach recognizes that the overall regulation of decomposer activity is through the structure of soil, which determines... |
| Tipo: Journal paper |
Palavras-chave: Soil quality. |
| Ano: 2001 |
URL: http://orgprints.org/333/1/Physical_fractionation_orgprints.pdf |
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| Christensen, B.T.; Rasmussen, J.; Eriksen, J.; Hansen, E.M.. |
| The inclusion of leys in arable cropping is generally found to improve soil fertility. The effect of leys depends on their botanical composition and management, but the significance of individual management factors remains confounded in most studies. We quantified the effects of one- to six-year-old pure grass leys on soil C (0-20 cm) and yields of three subsequent test crops of spring barley (Hordeum vulgare) under-sown with Italian ryegrass (Lolium perenne). Each ley was a mixture of four grass species (Lolium perenne, Festuca pratensis, Phleum pratense, Poa pratensis), exposed to three to four cuts annually. Only mineral fertilizers were applied (225 kg N ha-1 yr-1). The yield of barley was tested at six rates of N fertilizer (0 to 150 kg N ha-1). The... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover; Crop combinations and interactions; Air and water emissions. |
| Ano: 2009 |
URL: http://orgprints.org/16289/1/16289.pdf |
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| Petersen, Søren O.; Schjønning, P.; Olesen, Jørgen E.; Christensen, S.; Christensen, B.T.. |
| In organic cropping systems, legumes, cover crops, residue incorporation, and manure application are used to maintain soil fertility, but the contributions of these management practices to soil nitrogen (N) supply remain obscure. We examined potential sources of N for winter wheat (Triticum aestivum L.) in four experimental cropping systems established in 1997 on three soil types. Three of the four systems were under organic management. Topsoil N, depth of the A horizon, and cumulated inputs of N since 1997 were determined at plot level. Labile soil N pools (mineral N, potentially mineralizable N [PMN], microbial biomass N [MBN]) were monitored during two growth periods; at one site, biomass C/N ratios were also determined. Soil for labile N analysis was... |
| Tipo: Journal paper |
Palavras-chave: Crop combinations and interactions; Soil biology; Nutrient turnover; Farm nutrient management. |
| Ano: 2013 |
URL: http://orgprints.org/22015/7/22015.pdf |
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| Schjønning, P.; Elmholt, S.; Christensen, B.T.. |
| The industrialization of agriculture and the concurrent increase in societal concerns on environmental protection and food quality have put focus on agricultural management and its impact on soil quality. Soil quality involves the ability of the soil to maintain an appropriate productivity, while simultaneously reducing the effect on the environment and contributing to human health. This development has changed society’s expectations to science and there is an urgent need to improve the communication among researchers from different scientific disciplines. The interaction of scientists with decision-makers is a topic of utmost relevance for future developments in agriculture. Reflexive objectivity denotes the exercise of raising one’s consciousness of the... |
| Tipo: Book chapter |
Palavras-chave: Research methodology and philosophy; Soil. |
| Ano: 2004 |
URL: http://orgprints.org/1470/1/A4659_Schjonning_Chap01.pdf |
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| Christensen, B.T.. |
| The availability of nitrogen to crop plants is a universally important aspect of soil quality, and often nitrogen represents the immediate limitation to crop productivity in modern agriculture. Nitrogen is decisive for the nutritive value of plant products and plays a key role in the environmental impact of agricultural production. The fundamental doctrine of nitrogen management is to optimise the nitrogen use efficiency of both introduced and native soil nitrogen by increasing the temporal and the spatial coincidence between availability and root uptake of mineral nitrogen. Natural ecosystems have evolved to produce a high degree of coincidence and maintain a relatively tight nitrogen cycle. The management needed to assure the vitality of crop cultivars... |
| Tipo: Book chapter |
Palavras-chave: Farming Systems. |
| Ano: 2004 |
URL: http://orgprints.org/335/1/Tightenen_N_cycle.pdf |
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| Cong, W.-F.; Christensen, B.T.; Eriksen, J.. |
| The response of above- and below-ground biomass to soil nutrient availability is crucial for estimating belowground carbon input and predicting changes in soil carbon storage. However, the response is far from clear at plant community level, especially for grassland systems. Using a long-term field experiment initiated 123 years ago with varying soil nutrient levels (deficient, sub-optimal, optimal and over-optimal) established by use of two nutrient sources (animal manure or mineral fertiliser), we examined the effects of soil nutrient level and source on herbage yield and composition, root biomass and root-to-shoot (R/S) ratio of an unfertilised multispecies grass-legume ley. Increased nutrient levels enhanced herbage yield, but did not affect root... |
| Tipo: Journal paper |
Palavras-chave: Crop combinations and interactions; Nutrient turnover. |
| Ano: 2018 |
URL: http://orgprints.org/34981/1/Cong%20et%20al.%202019%20AGEE.pdf |
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| Christensen, B.T.; Johnston, A.E.. |
| The various elements of an arable cropping system, such as crop type and cultivar, soil tillage, crop protection measures, use of mineral fertilizers and animal manure, crop-residue disposal, and addition of town-derived organic refuses all interact in a complex manner with basic soil properties (texture and mineralogy), and this interaction determines the general productivity of the cropping system. The same elements also influence soil organic matter (SOM) turnover, some more than others. The SOM holds large pools of organically bound plant nutrients, which, through mineralization, may become available for crop uptake or loss from the soil-plant system through leaching or gaseous losses. Additionally, SOM is important to both soil structure and the... |
| Tipo: Book chapter |
Palavras-chave: Soil quality. |
| Ano: 1997 |
URL: http://orgprints.org/424/1/Soil_organic_matter_and_quality.pdf |
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| Schjønning, P.; Heckrath, G.; Christensen, B.T.. |
| The EU Commission is preparing a proposal for a Soil Framework Directive with the purpose of protecting the soil resources in Europe. The proposal identifies six major threats to the sustained quality of soils in Europe. This report addresses the threats that are considered most important under the prevailing soil and climatic conditions in Denmark: compaction, soil organic matter decline, and erosion by water and tillage. For each of these threats, the relevance and damage to soil functions as well as the geographic distribution in Denmark are outlined. We suggest a procedure for identifying areas at risk. This exercise involves an explicit identification of: i) the disturbing agent (climate / management) exerting the pressures on soil, and ii) the... |
| Tipo: Report |
Palavras-chave: Soil quality. |
| Ano: 2009 |
URL: http://orgprints.org/18446/1/18446.pdf |
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| Nørbæk, R.; Folsted, D.; Bleeg, I.S.; Christensen, B.T.; Brandt, K.; Kondo, T.. |
| From the leaves of barley, Hordeum vulgare, one new flavone C-glucoside and three known flavone glucosides were isolated and characterized by 1H, 13C NMR and MALDITOF-MS. The novel flavone C-glucoside was isovitexin 7-O-b-(6’’’-O-(E)-p-coumaroyl)glucoside and the known compounds were isovitexin 7-O-b-(6’’’-O-(E)-feruloyl)glucoside, isoorientin 7-O-b-(6’’’-O-(E)-feruloyl)glucoside and tricin 7-O-b-glucoside. The sum of all the flavone glycosides and soluble phenolic acids in the leaves decreased with increased rate of plant nutrients given in animal manure and with increased crop yield. All major phenylpropanoids showed the same general response to nutrient level. The concentration of nitrogen in the leaves was not directly related to nutrient application... |
| Tipo: Journal paper |
Palavras-chave: Crop husbandry. |
| Ano: 2003 |
URL: http://orgprints.org/338/1/A%2Dmanuscript.pdf |
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| Schjønning, P.; de Jonge, L.W.; Munkholm, L.J.; Moldrup, P.; Christensen, B.T.; Olesen, J.E.. |
| Soil organic carbon (OC) influences clay dispersibility, which affects soil tilth conditions and the risk of vertical migration of clay colloids. No universal lower threshold of OC has been identified for satisfactory stabilization of soil structure. We tested the concept of clay saturation with OC as a predictor of clay dispersibility and soil friability. Soil was sampled three years in a field varying in clay content (~100 to ~220 g kg-1 soil) and grown with different crop rotations. Clay dispersibility was measured after end-over-end shaking of field-moist soil and 1-2 mm sized aggregates either air-dried or rewetted to -100 hPa matric potential. Tensile strength of 1-2, 2-4, 4-8 and 8-16 mm air-dried aggregates was calculated from their compressive... |
| Tipo: Journal paper |
Palavras-chave: Soil quality. |
| Ano: 2011 |
URL: http://orgprints.org/18939/4/18939.pdf |
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| Schjønning, P.; Elmholt, S.; Christensen, B.T.. |
| There is an urgent need to analyse the term soil quality in more detail. Most frequently, it is used to describe soil attributes. The term should be used for this purpose only when related to the sustainability concerns (i) soil productivity, (ii) impact on the environment, and (iii) effect on human health. The soil quality concept has been adopted mainly as a technical framework for grading soil and evaluating management effects. We advocate more focus on soil quality as a cognitive concept associated with sustainability. Grading of soils by indicators is difficult across soil types, climates and cropping systems. The indexing of soil quality indicators introduce a significant loss of information on the complex agroecosystem. The contributions to the... |
| Tipo: Book chapter |
Palavras-chave: Research methodology and philosophy; Soil. |
| Ano: 2004 |
URL: http://orgprints.org/1471/1/Chapt01_tex_ref_final.doc |
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| Thomsen, I.K.; Schjønning, P.; Jensen, B.; Kristensen, K.; Christensen, B.T.. |
| To evaluate the effect of soil texture and soil water content on decomposition of organic carbon (OC), turnover of partially stabilized 14C-labelled ryegrass residues was studied at four matric potentials in twelve differently textured soils of similar origin and cropping history. Six soils were from a naturally occurring clay gradient and had 11, 16, 21, 31, 37 and 45% clay (termed NA1 to NA6). Three clay-amended soils (CL2, CL4, CL6) and three silt-amended soils (SI2, SI4, SI6) were prepared by adding clay or silt sized organomineral complexes extracted from the NA2 soil to a portion of the NA1 soil. After 14C-labelled ryegrass had decomposed for eight months under field-like conditions, soil cores were sampled, adjusted to four matric potentials (-30,... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover; Soil quality; Soil biology. |
| Ano: 1999 |
URL: http://orgprints.org/727/1/geoderma_99_II.pdf |
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| Registros recuperados: 16 | |
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