Tracking the photosynthesized carbon input into soil organic carbon pools in a rice soil fertilized with nitrogen
Replenishment of soils with carbon (C) produced during photosynthesis plays an important role in global C cycling. Nitrogen (N) fertilization is critical for rice production, but its effects on the deposition of photosynthesis-derived C into soil C pools is poorly understood. To address this, we used continuous 14C-labeling to quantify the deposition of photosynthesis-derived C into various soil organic pools in a rice-soil system.
Rice (Oryza sativa L.) was continuously supplied with 14C-labeled CO2 (14C-CO2) for 36 days, with increasing N fertilizer rates (0 [N0], 10 [N10], 20 [N20], or 40 mg N kg−1 soil [N40], respectively).
Rice shoot and root biomass significantly increased following N fertilization. The amount of photosynthesis-derived C converted into soil organic carbon (14C-SOC) was proportional to the soil N concentration, and accounted for 8.0–19.3 % of rice biomass C. The 14C-SOC content was positively correlated with the rice root biomass, suggesting that N increased root exudation of photosynthesis-derived C. The amounts of 14C-labeled C in the dissolved organic carbon (14C-DOC) and in the microbial biomass carbon (14C-MBC), as proportions of 14C-SOC, were 3.9–7.8 and 6.6–24.0 %, respectively. The 14C-DOC, 14C-MBC, and 14C-SOC as proportions of total DOC, MBC, and SOC were 9.7–11.6, 6.9–10.6, and 0.37–1.71 %, respectively.
Nitrogen fertilization promotes deposition of photosynthesis-derived C into SOC pools in a rate-dependent manner. However, the 14C-MBC as a proportion of both 14C-SOC (14C-MBC/14C-SOC) and MBC (14C-MBC/MBC) increase during rice growth at lower N concentrations.
KeywordsSoil organic C Rice N application rate 14C labeling Photo-assimilated C
This study was supported financially by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB15020401), the National Natural Science Foundation of China (41301275; 41430860) and the Research Fund of State Key Laboratory of Soil and Sustainable Agriculture, Nanjing Institute of Soil Science, Chinese Academy of Science (Y412201410). We thank Editage for editorial assistance.
- FAO (2011) Rice market monitor. April 2011. XIV(2). P2. http://www.fao.org/docrep/014/am491e/am491e00.pdf
- Gong ZT, Zhang GL, Chen ZC (eds) (2009) Pedogenesis and soil taxonomy. Science Press, Beijing, pp 613–626, in ChineseGoogle Scholar
- Yuan HZ, Ge TD, Zou SY, Wu XH, Liu SL, Zhou P, Chen XJ, Brookes P, Wu JS (2013) Effect of land use on the abundance and diversity of autotrophic bacteria as measured by ribulose-1, 5-biphosphate carboxylase/oxygenase (RubisCO) large-subunit gene abundance in soils. Biol Fertil Soils 49:609–616CrossRefGoogle Scholar