Mineralisation dans le sol de materiaux microbiens marques au carbone 14 et a l'azote 15: Quantification de l'azote de la biomasse microbienne |
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| Affiliation: | 1. Laboratoire de Génie Chimique, CNRS, Université de Toulouse, 4 allée Emile Monso, 31432 Toulouse, France;2. IRSTEA-Unité de Recherche Hydrosystèmes et Bioprocédés, 1 rue Pierre-Gilles de Gennes, CS 10030, 92761 Antony, France;1. Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84604, United States of America;2. Department of Chemical Engineering, Brigham Young University, Provo, UT 84602, United States of America;1. State Key Lab of Hydrology-Water Resources & Hydraulic Engineering, College of Hydrology & Water Resource, Hohai University, Nanjing, Jiangsu 210098, PR China;2. School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China;3. School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan, Hubei 430072, China;4. Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA;5. Shenzhen Municipal Engineering Lab of Environmental IoT Technologies, Southern University of Science and Technology, Shenzhen 518055, Guangdong Province, China;6. School of Mathematics and Big Data, Anhui University of Science & Technology, Huainan 232001, China |
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| Abstract: | The mineralization of microbial material of different C-to-N ratios (5.2, 7.9, 10.2, 12.7) was followed in fumigated soil. The microbial materials used were from Aspergillus flavus cultures, grown in liquid media and labelled with [14C]glucose and (15NN4)3804. Three contrasting soils were used and the microbial materials incubated with the fumigated soils for 28 days at 28°C.The evolution of the added organic microbial C was fast: 80% of the [14C]CO2 produced during the whole 28 days incubation was evolved in the first week. Microbial C mineralization was mainly related to soil type; the C-to-N ratio had small effect on the ratio (mineralized microbial carbon-to-added microbial carbon). Calculation of the Kc- coefficient (the fraction of the added microbial C mineralized in 7 days) shows that Kc values lie between 0.38 and 0.43 in the 3 soils.Organic N in the added microbial material also breaks down quickly: between 60 and 100% of the organic nitrogen mineralized was evolved during the first week of incubation. Mineralization kinetics are related to soil type and to the C-to-N ratio of the microbial material.The proportion of N mineralized in 7 days was lower in an acid soil than in near neutral soils and lower with high C-to-N ratio material than with low C-to-N ratio material. The ratio (mineralized microbial N-to-added microbial N) depends on soil type and is negatively correlated with the C-to-N ratio of the microbial material. The KN value (the fraction of the added microbial N mineralized in 7 days) lies between 0.22 and 0.47 for the three soils and four materials investigated. The added microbial material induced a priming effect on soil native N: materials with C-to-N ratios of 10.2 and 12.7 produced negative priming effects whereas materials with C-to-N ratios of 5.2 and 7.9 sometimes produced a positive priming action.From the relationship between the C-to-N ratio of the added material and the (mineralized microbial C-to-mineralized microbial N) ratio, the soil native microbial biomass was estimated using the fiush-C-to-flush-N ratio. Biomass nitrogen was then calculated from the formula biomass-N = biomassC/(biomass C-to-N ratio). Calculated in this way, 2–4% of the total nitrogen in the three soils was in microbial biomass. |
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