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| Høgh-Jensen, Henning; Loges, Ralf; Jensen, Erik Steen; Jørgensen, Finn V.; Vinther, Finn P.. |
| Symbiotically fixed N2 (SNF) is an important input of nitrogen (N) in many cropping systems. In spite of this fact, the input of fixed N to a particular cropping system is usually not known, and an exact estimation of the amount of N2 fixed requires laborious measurements. Consequently, there is a demand for a simple and reliable tool to estimate N2 fixation in leguminous crops. A model is here proposed for quantification of SNF in leguminous crops in different arable systems. The model estimates SNF using dry matter yield as input and cropping system specific values for the parameters: N concentration in dry matter and the proportion of the N in the legume that is derived from the atmosphere. Further, the model includes fixed N not included in the... |
| Tipo: Journal paper |
Palavras-chave: Production systems. |
| Ano: 2003 |
URL: http://orgprints.org/316/1/Emperical_N2%2Dfixation_eng_v6.doc |
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| Høgh-Jensen, Henning; Loges, Ralf; Jensen, Erik Steen; Jørgensen, Finn V.; Vinther, Finn P.. |
| Symbiotically fixed nitrogen (N2) is an important input of nitrogen (N) source in many agricultural systems. In spite of this fact, the input of symbiotically fixed N to a particular cropping system is usually not known and exact measurements are costly and laborious. Consequently, there is a demand for an uncomplicated and reliable tool to estimate symbiotic N2 fixation (SNF) in leguminous crops. A simple emperical model is proposed for quantification of SNF in forage legumes under low external input conditions. The model estimates SNF using dry matter yield as input and parameters for (i)N concentration in dry matter and the (ii) proportion of the N in the legume that is derived from the atmosphere. Further, the model includes fixed N not included in the... |
| Tipo: Journal paper |
Palavras-chave: Pasture and forage crops. |
| Ano: 2004 |
URL: http://orgprints.org/3085/1/emperical_model.pdf |
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| Vinther, Finn P.; Jensen, Erik S.. |
| The input of N through symbiotic N2 fixation (SNF) in grass-clover mixtures was determined in an organic cropping system for grazing during three years. The mixture of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) was established by undersowing in spring barley (Hordeum vulgare L.) and maintained subsequently for two production years. Dinitrogen fixation was determined using the 15N isotope dilution techniques and two labelling procedures. Using either pre-labelling of the soil with immobilisation of the 15N by addition of a carbon source before establishment of the grass-clover mixture or adding the 15N labelled ammonium to the established crop, resulted in similar estimates of the proportion of N derived from the... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover; Soil quality; Soil biology; Pasture and forage crops. |
| Ano: 2000 |
URL: http://orgprints.org/167/2/vinther_and_Jensen_2000.pdf |
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| Hansen, Jacob P.; Vinther, Finn P.. |
| Aiming at estimating the spatial variability in N2 fixation, and to evaluate the appropriateness of the 15N isotope dilution (ID) method and the natural 15N abundance (NA) method in reflecting spatial variability under the influence of cattle grazing, the symbiotic N2 fixation in grass-white clover mixture was studied. At the Foulum site, where the ID method was used, differences in the climatic conditions between the two years of investigations caused a considerable difference in plant growth rates and proportion of clover. Consequently, the total N2 fixation in ungrazed reference plots was significantly less in 1998 than in 1997, being 5.9 and 12.5 g N m-2, respectively. In both years there was a wide range in concentration of inorganic N in the soil... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover; Soil quality; Soil biology; Pasture and forage crops. |
| Ano: 2001 |
URL: http://orgprints.org/172/1/Hansen_og_Vinther_2001.pdf |
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| Vinther, Finn P.; Hansen, Søren. |
| Denitrifikationen, som er særdeles vigtig både i landbrugs- og miljømæssig henseende, er en af de vanskeligste processer i kvælstof kredsløbet at kvantificere, idet den er kendetegnet ved en stor rumlig og tidslig variation. Der er brug for mange ressourcekrævende målinger for med rimelig sikkerhed at kvantificere denitrifikationen på markniveau. Eksperimentel bestemmelse af denitrifikationen er derfor oftest udelukket, og man må ty til matematiske modeller, hvis man ønsker at estimere hvad denitrifikationen har været, eller ønsker at vide hvad denitrifikationen måtte blive ved en given ændring i landbrugspraksis. Også modeller kan dog være vanskelige at håndtere, idet de fleste modeller kræver adgang til flere baggrundsoplysninger end det oftest er muligt... |
| Tipo: Report |
Palavras-chave: Nutrient turnover; Air and water emissions. |
| Ano: 2004 |
URL: http://orgprints.org/3139/1/SimDen.pdf |
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