[Responses of organic carbon mineralization and priming effect to phosphorus addition in paddy soils].

To understand the coupled controlling of carbon (C) and phosphorus (P) on the minera-lization of soil organic carbon and amended substrates in paddy soil, we investigated the effects of P addition on the decomposition of organic carbon and its induced priming effect by using ¹³ C isotope probing technique in microcosm. The results showed that P addition accelerated the release of CO ₂ but inhibited the release of CH ₄ , leading to 53.1% reduction of total accumulated CH ₄ and 70.5% reduction of the ¹³ CH ₄ derived from exotic glucose- ¹³ C. P addition altered the carbon distribution during the microbial turnover progress, with 3.6% of glucose- ¹³ C being transferred into the labile carbon pool, therein significantly increased potential of the mineralization rate of exogenous C. A transient negative priming effect was observed in the early stage of incubation. With time prolonging, the priming effect on CO ₂ emission (PE _{CO 2} ) generally increased and then decreased after a peak. The priming effect on CH ₄ emission (PE _{CH 4} ) kept increasing and finally fluctuated at a relative stable value until the end of the experiment (100 days). P addition increased PE _{CO 2} by 32.3% but reduced PE _{CH 4} by 93.4%. Results from the RDA and Pearson analysis showed that electric conductivity, oxidation-reduction potential and dissolved organic carbon significantly affected soil C mineralization. There were significantly negative correlations between available phosphorus (Olsen-P) and ¹³ CH ₄ , and between Olsen-P and PE _{CH 4} . In conclusion, with the addition of exogenous organic matter, P application could reduce CH ₄ emissions and inhibit its priming effect, acce-lerate the mineralization of SOC, probably improve the nutrient supply, and thus enhance the avai-lability of organic C and promote C cycling in paddy soil.