Influence of light intensity on the distribution of carbon and consequent effects on mineralization of soil nitrogen in a barley (Hordeum vulgare L.)-soil system |
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Authors: | Erick Zagal |
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Institution: | (1) Department of Soil Sciences, Division of Plant Nutrition and Soil Fertility, Swedish University of Agricultural Sciences, P.O. Box 7014, S-750 07 Uppsala, Sweden |
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Abstract: | A pot experiment was conducted in a 14C-labelled atmosphere to study the influence of living plants on organic-N mineralization. The soil organic matter had been labelled, by means of a 200-days incubation, with 15N. The influence of the carbon input from the roots on the formation of microbial biomass was evaluated by using two different light intensities (I). Mineralization of 15N-labelled soil N was examined by following its fate in both the soil biomass and the plants. Less dry matter accumulated in shoots and roots at the lower light intensity. Furthermore, in all the plant-soil compartments examined, with the exception of rhizosphere respiration, the proportion of net assimilated 14C was lower in the low-I treatment than in the high-I treatment. The lower rates of 14C and 15N incorporation into the soil biomass were associated with less root-derived 14C. During the chamber period (14CO2-atmosphere), mineralized amounts of 15N (measured as plant uptake of 15N) were small and represented about 6.8 to 7.8% of the initial amount of organic 15N in the soil. Amounts of unlabelled N found in the plants, as a percentage of total soil N, were 2.5 to 3.3%. The low availability of labelled N to microorganisms was the result of its stabilization during the 210 days of soil incubation. Differences in carbon supply resulted in different rates of N mineralization which is consistent with the hypothesis that roots induce N mineralization. N mineralization was higher in the high-I treatment. On the other hand, the rate of mineralization of unlabelled stable soil N was lower than labelled soil 15N which was stabilized. The amounts of 15N mineralized in planted soil during the chamber period (43 days) which were comparable with those mineralized in unplanted soil incubated for 210 days, also suggested that living plants increased the turnover rate of soil organic matter. |
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Keywords: | 14C 15N fertilizer native soil organic matter pot experiment root-induced mineralization soil biomass |
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