[Responses of organic carbon mineralization and priming effect to phosphorus addition in paddy soils]. / ç¨»ç”°åœŸå£¤æœ‰æœºç¢³çŸ¿åŒ–åŠå ¶æ¿€å‘æ•ˆåº”å¯¹ç£·æ·»åŠ çš„å“åº”.

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 (PECO2) generally increased and then decreased after a peak. The priming effect on CH4 emission (PECH4) kept increasing and finally fluctuated at a relative stable value until the end of the experiment (100 days). P addition increased PECO2 by 32.3% but reduced PECH4 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 PECH4. 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.

[Effects of straw returning combined with medium and microelements application on soil organic carbon sequestration in cropland.] / ç§¸ç§†è¿˜ç”°é æ–½ä¸­å¾®é‡å ƒç´ å¯¹å†œç”°åœŸå£¤æœ‰æœºç¢³å›ºæŒçš„å½±å“.

A 52-day incubation experiment was conducted to investigate the effects of maize straw decomposition with combined medium element (S) and microelements (Fe and Zn) application on arable soil organic carbon sequestration. During the straw decomposition, the soil microbial biomass carbon (MBC) content and CO2-C mineralization rate increased with the addition of S, Fe and Zn, respectively. Also, the cumulative CO2-C efflux after 52-day laboratory incubation significantly increased in the treatments with S, or Fe, or Zn addition, while there was no significant reduction of soil organic carbon content in the treatments. In addition, Fe or Zn application increased the inert C pools and their proportion, and apparent balance of soil organic carbon, indicating a promoting effect of Fe or Zn addition on soil organic carbon sequestration. In contrast, S addition decreased the proportion of inert C pools and apparent balance of soil organic carbon, indicating an adverse effect of S addition on soil organic carbon sequestration. The results suggested that when nitrogen and phosphorus fertilizers were applied, inclusion of S, or Fe, or Zn in straw incorporation could promote soil organic carbon mineralization process, while organic carbon sequestration was favored by Fe or Zn addition, but not by S addition.