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Titre :
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Nitrifier populations and nitrification rates in agricultural soil
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Auteurs :
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P. Berg ;
SWAEDISH UNIVERSITY OF AGRICULTURAL SCIENCES
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Type de document :
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thèse/mémoire
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Editeur :
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S.E., 1986
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Collection :
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Rapport 34
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Format :
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100 p.
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Langues:
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= Anglais
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Catégories :
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Agriculture
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Mots-clés:
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NITRIFICATION
;
NITRATE
;
AGRICULTURE
;
SOL
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Résumé :
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Nitrifier populations and nitrification rates were studied in four arable cropping systems ( fertilized grass ley and barley and unfertilized lucerne ley and barley ) over three years. Numbers of nitrifierss were determined with the Most Probable Number ( MPN ) technique. Potential nitrification rates were assessed with was developed to measure actual nitrification rates in the field. MPN counts showed great amplitude while potential rates showed smaller variations. Numbers and activities of ammonium oxidizers correlated with water potential in a long-term experiment conducted over ten months. Short-term regulatory factors were temperature, ammonium concentration and water potential. Optimum soil water potential for nitrification was -0.11 MPa ( 65% WHC ). A Q10 of 1.7 was found for ammonium oxidation in incubated soil and a Km of about 20 was found for field conditions ( pH 6.3 and 15° C ) . Potential ammonium- and nitrite oxidation rates were stimulated in the root zone of young (three weeks) barley plants. A coupling was indicated in the root zone between nitrite oxidation and nitrate reduction. Ammonium oxidation was positevely correlated with the organic matter content in a soil from a 27 year old field trial, with a fallow and four different cropping treatments. Actual ammonium oxidation measurements were proposed to correspond to actual in situ activity at the moment of sampling, whereas the MPN technique and the potential measurements reflected events that occurred weeks or months before the sampling. Nitrification was totally inhinited at 10 Pa partial pressure of C2H2. The inhibiting effect did not cease until 7 days after removal of C2H2.
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Diplôme :
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Ph D thesis - Swedish University of agricultural sciences, Uppsala, suéde
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En ligne :
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http://www.vaxteko.nu/html/sll/slu/rapport_mikrobiologi/RMB34/RMB34.HTM
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