[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 ¹³C isotope probing technique in microcosm. The results showed that P addition accelerated the release of CO₂ but inhibited the release of CH₄, leading to 53.1% reduction of total accumulated CH₄ and 70.5% reduction of the ¹³CH₄ derived from exotic glucose-¹³C. P addition altered the carbon distribution during the microbial turnover progress, with 3.6% of glucose-¹³C 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 CO₂ emission (PE_CO) generally increased and then decreased after a peak. The priming effect on CH₄ emission (PE_CH) kept increasing and finally fluctuated at a relative stable value until the end of the experiment (100 days). P addition increased PE_CO by 32.3% but reduced PE_CH 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 ¹³CH₄, and between Olsen-P and PE_CH. In conclusion, with the addition of exogenous organic matter, P application could reduce CH₄ 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.