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| Registros recuperados: 52 | |
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| Schjønning, P.. |
| I økologisk jordbrug anvendes alsidige sædskifter, efterafgrøder og/eller tildeling af husdyrgødning/halm/kompost. Alt dette er med til at fremme mængden af organisk stof i jorden, som normalt forventes at spille en stor rolle for strukturen og poresystemet (jordens hulrum). FØJO har gennemført en række undersøgelser for at afdække, hvor meget og hvordan man som landmand kan påvirke forholdene. De langvarige forsøg med forskellig gødskning på Askov Forsøgsstation giver et godt grundlag for at vurdere effekten af organisk stof på jordens poresystem. Ca. 100 års forsøg uden tilførsel af nogen form for gødning har resulteret i et indhold af organisk stof i jorden på kun ca. 1% (svarende til et humusindhold på ca. 1,7%). Brug af mineralsk gødning (NPK) har... |
| Tipo: Newspaper or magazine article |
Palavras-chave: Crop combinations and interactions; Soil biology; Soil quality; Composting and manuring. |
| Ano: 2004 |
URL: http://orgprints.org/7757/1/7757.doc |
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| Thomsen, I. K.; Schjønning, P.; Olesen, J.E.; Christensen, B. T.. |
| The turnover of native and applied C and N in undisturbed soil samples of different texture but similar mineralogical composition, origin and cropping history was evaluated at –10 kPa water potential. Cores of structurally intact soil with 108, 224 and 337 g clay kg-1 were horizontially sliced and 15N-labelled sheep faeces was placed between the two halves of the intact core. The cores together with unamended treatments were incubated in the dark at 20°C and the evolution of CO2-C determined continuously for 177 d. Inorganic and microbial biomass N and 15N were determined periodically. Net nitrification was less in soil amended with faeces compared with unamended soil. When adjusted for the NO3-N present in soil before faeces was applied, net nitrification... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover. |
| Ano: 2003 |
URL: http://orgprints.org/272/1/HarmTaskArev.doc |
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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.; Iversen, B.V.; Jacobsen, O.H.. |
| Mængden af organisk stof, som man påvirker med almindelig landbrugsdrift, har ikke nævneværdig indflydelse på jordens vandholdende evne. Anvendelse af husdyrgødning i stedet for mineralsk gødning kan heller ikke forventes at påvirke jordens ledningsevne for vand i pløjelaget. I forhold til ekstreme driftsformer med et ensidigt (korn-)sædskifte og uden anvendelse af organisk gødning vil en økologisk driftsform give både et større porevolumen og et mere forgrenet poresystem. Et højt næringsstofniveau giver – uanset tildelingsmetode – flere store porer og bedre ledningsevne for vand i jordlaget under pløjedybde. |
| Tipo: Journal paper |
Palavras-chave: Crop combinations and interactions; Soil quality; Composting and manuring. |
| Ano: 2004 |
URL: http://orgprints.org/7763/1/7763.doc |
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| Schjønning, P.; Jørgensen, M.H.; Olesen, J.E.; Rasmussen, G.; Munkholm, L.J.; Melander, B.. |
| Der er fra det danske landbrugserhverv formuleret ønske om, at der iværksættes en bedre rådgivning omkring gennemførelse af reduceret jordbearbejdning, herunder direkte såning (FRDK, bl.a. ved mødet i Forskningskontoret 18. januar 2001). Problemstillingen har interesse for såvel konventionelle som økologiske jordbrugere, idet reduceret bearbejdning af jorden som udgangspunkt er positivt for jordkvaliteten. Der er gennemført en lang række undersøgelser omkring reduceret jordbearbejdning og direkte såning i Danmark. En række forhold har dog til dels gjort disse resultater forældede. Det skyldes bl.a. den politisk bestemte udvikling i de dyrkede afgrøder, herunder i særlig grad sædskiftet, som har stor betydning for reduceret jordbearbejdning. De gennemførte... |
| Tipo: Report |
Palavras-chave: Production systems; Soil tillage; Farming Systems; Soil. |
| Ano: 2001 |
URL: http://orgprints.org/730/1/redj_not.doc |
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| Schjønning, P.. |
| • Jordkvalitet har to aspekter: 1) graduering god/dårlig og 2) behov og ønsker. Den amerikanske tilgang fokuserer næsten udelukkende på det første aspekt, hvorfor værdier og prioriteringer ikke er eksplicitte. Det giver kommunikationsproblemer og uklare løsninger • Den af DJF gennemførte udredning om effekter af jordbrugs-metoder på jordkvalitet påviste behovet for eksplicit håndtering af værdier og prioriteringer i forsknings- og planlægningsarbejde • Samme arbejde påpegede problemer med ikke-universalitet af indikatorer og – ikke mindst – indekser for jordkvalitet. I stedet peges på management-fokuseret problemløsning i tværfaglige projektgrupper • Den foreliggende EU tematiske strategi for jordbeskyttelse har gennem anvendelse af DPSIR-konceptet... |
| Tipo: Conference paper, poster, etc. |
Palavras-chave: Regulation Education; Extension and communication Soil quality. |
| Ano: 2004 |
URL: http://orgprints.org/7765/1/7765.pdf |
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| Schjønning, P.; Thomsen, I. K.; Moldrup, P.; Christensen, B. T.. |
| Quantification of in situ soil microbial activity is indispensable in order to improve manipulation of nutrient turnover in soil and optimize crop nutrient supply. We sampled 100 cm3 cores of undisturbed arable soil at three locations along a naturally occurring clay gradient (L1: 11% clay; L3: 22% clay; L5: 34 % clay). The cores were drained to seven different matric potentials in the range –15 to –1500 hPa and gas diffusion determined prior to a 4 week incubation at 20oC in the dark. For all soils the net nitrification increased with water content to a maximum (L1: 12.1, L3: 10.3 and L5: 8.2 g NO3-N g-1 soil) and then decreased with further increase in water content. The water content at maximum nitrification was 0.26, 0.37 and 0.42 m3 m-3,... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover. |
| Ano: 2003 |
URL: http://orgprints.org/273/1/MS_S02%2D0112_text.doc |
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| Petersen, Søren O.; Ambus, Per; Elsgaard, Lars; Schjønning, P.; Olesen, Jørgen E.. |
| The potential for N2O emissions outside the main growing season may be influenced by long-term effects of cropping system. This was investigated by collecting intact soil cores (100 cm3, 0-4 cm depth) under winter wheat in three organic cropping systems and a conventional reference within a long-term crop rotation experiment. Average annual inputs of C in crop residues and manure ranged from 1.7 to 3.3 Mg ha-1. A simulated freeze-thaw cycle resulted in a flush of CO2 during the first 48 h, which could be mainly from microbial sources. Other samples were adjusted to approximately –10, -30 or –100 hPa and amended with excess 15NO3- prior to freezing and thawing. Denitrification was the main source of N2O during a 72-h incubation at 22C, as judged from N2O... |
| Tipo: Journal paper |
Palavras-chave: Soil biology; Air and water emissions; Farm nutrient management. |
| Ano: 2013 |
URL: http://orgprints.org/22014/1/22014.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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| Registros recuperados: 52 | |
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