Nitrogen fertilization increases rhizodeposit incorporation into microbial biomass and reduces soil organic matter losses
2017 | journal article. A publication with affiliation to the University of Göttingen.
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Nitrogen fertilization increases rhizodeposit incorporation into microbial biomass and reduces soil organic matter losses
Zang, H.; Blagodatskaya, E. V. ; Wang, J.; Xu, X. & Kuzyakov, Y. (2017)
Biology and Fertility of Soils, 53(4) pp. 419-429. DOI: https://doi.org/10.1007/s00374-017-1194-0
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- Authors
- Zang, Huadong; Blagodatskaya, Evgenia V. ; Wang, J.; Xu, X.; Kuzyakov, Yakov
- Abstract
- Agricultural soils receive large amounts of anthropogenic nitrogen (N), which directly and indirectly affect soil organic matter (SOM) stocks and CO2 fluxes. However, our current understanding of mechanisms on how N fertilization affects SOM pools of various ages and turnover remains poor. The delta C-13 values of SOM after wheat (C-3)-maize (C-4) vegetation change were used to calculate the contribution of C-4-derived rhizodeposited C (rhizo-C) and C-3-derived SOM pools, i.e., rhizo-C and SOM. Soil (Ap from Haplic Luvisol) sampled from maize rhizosphere was incubated over 56 days with increasing N fertilization (four levels up to 300 kg N ha(-1)), and CO2 efflux and its delta C-13 were measured. Nitrogen fertilization decreased CO2 efflux by 27-42% as compared to unfertilized soil. This CO2 decrease was mainly caused by the retardation of SOM (C-3) mineralization. Microbial availability of rhizo-C (released by maize roots within 4 weeks) was about 10 times higher than that of SOM (older than 4 weeks). Microbial biomass and dissolved organic C remained at the same level with increasing N. However, N fertilization increased the relative contribution of rhizo-C to microbial biomass by two to five times and to CO2 for about two times. This increased contribution of rhizo-C reflects strongly accelerated microbial biomass turnover by N addition. The decomposition rate of rhizo-C was 3.7 times faster than that of SOM, and it increased additionally by 6.5 times under 300 kg N ha(-1) N fertilization. This is the first report estimating the turnover and incorporation of very recent rhizo-C (4 weeks old) into soil C pools and shows that the turnover of rhizo-C was much faster than that of SOM. We conclude that the contribution of rhizo-C to CO2 and to microbial biomass is highly dependent on N fertilization. Despite acceleration of rhizo-C turnover, the increased N fertilization facilitates C sequestration by decreasing SOM decomposition.
- Issue Date
- 2017
- Status
- published
- Publisher
- Springer
- Journal
- Biology and Fertility of Soils
- ISSN
- 1432-0789; 0178-2762