农业生产对石灰性土壤无机碳库损失的影响

一般认为，土壤无机碳（SIC）周转缓慢，在全球农田碳循环及应对气候变化等方面的作用有限。近年来越来越多的证据表明，土壤无机碳转化速率也较快，在土壤肥力、碳库转化和调节大气二氧化碳浓度方面的作用不容小觑。总结了国内外关于农田无机碳方面的研究进展，强调无机碳在农田土壤固碳、缓冲土壤pH等方面具有重要作用；农业生产特别是氮肥大量施用导致我国一些地区农田无机碳消耗，加速土壤酸化，增加了作物重金属污染风险，影响了农田土壤健康。认为我国“秦岭-淮河”南北分界区非石灰性土壤与石灰性过渡区、山东半岛棕壤与潮土过渡区、东北黑土与黑钙土过渡区等区域SIC含量相对较低、降水量相对较高，长期大量施用氮肥会导致农田表层SIC发生损失，属SIC损失敏感区。提出应进一步研究的问题，包括：查明农业生产特别是施用氮肥对土壤无机碳去向的影响，研究土壤有机碳-二氧化碳-钙离子-无机碳相互作用机理及对氮肥的响应，在全球碳循环及土壤碳收支平衡研究中，应考虑人类活动特别是农业生产对土壤无机碳库的影响。建议定期监测我国无机碳损失敏感区农田土壤无机碳含量，合理施肥以减少土壤无机碳损失。

Effects of Agricultural Production on the Loss of Inorganic Carbon from Calcareous Soils

The turnover of soil inorganic carbon (SIC) is considered slowly and its role in carbon sequestration and climate change is limited. Therefore, the role of SIC in croplands to the global carbon cycle is rarely investigated. In recent years, more evidences have indicated that the turnover rate of SIC is much faster than was thought. This suggests that its roles in stabilizing soil fertility, global carbon pool, and regulating the concentration of carbon dioxide (CO2) in the atmosphere should not be ignored. Therefore, we have reviewed recent advances on SIC in croplands, paying special emphasis on the important role of SIC in sequestrating carbon and buffering soil pH. SIC loss in China induced by agricultural production, especially the application of nitrogen (N) fertilizers affects the health of croplands by accelerating soil acidification and increasing the risk of heavy metals pollution. Soils in the transition zones between the North and the South China (Qinling Huaihe River), brown soil and alluvial soil in the Shandong Peninsula, black soil and chernozem in Northeast China, have low carbonates and a vulnerable pool of SIC that is easily lost. Thus, we suggest that these regions should be designated as SIC loss vulnerable zones. For further studies, the following topics should be considered (i) understanding the fates of SIC and interactions of soil organic carbon-CO2-Ca-SIC in cropland induced by agricultural production, especially adding N fertilizers; (ii) SIC roles in carbon soil balance and cycle; and (iii) regular monitoring of the SIC content in the vulnerable zones. Also, for a sustainable reduction of SIC loss induced by soil acidification, the following measures should be considered: adequate application of N fertilizers, combining the application of N fertilizers with organic fertilizer and nitrification inhibitors and replacing the ammonium bearing fertilizers with nitrate fertilizer.