黄绵土中碳酸钙含量和有机肥施用对土壤有机碳组分及CO2排放的影响

为探讨碳酸钙(CaCO_3)和有机肥对土壤有机碳矿化和CO_2排放的影响,本研究通过向一种黄绵土中分别添加0、30、50 g·kg~(-1)CaCO_3模拟陕西省境内具有不同CaCO_3含量(9%~15%)的黄绵土,随后再添加0、20 g·kg~(-1)有机肥(M),交互组合设L0、L0-M、L30、L30-M、L50和L50-M等6个处理进行室内培养试验(105 d),测定了土壤pH、微生物量碳(MBC)、水溶性有机碳(DOC)、颗粒碳(POC)、易氧化有机碳(ROC)和CO_2释放量.结果表明:未施用有机肥时,土壤pH和MBC含量随CaCO_3含量的增加而增加,但CaCO_3含量对DOC、POC、ROC和有机碳氧化稳定性(Kos)无显著影响,其差异亦不会对土壤CO_2排放产生显著影响.当施用有机肥后,随着土壤CaCO_3含量增加,土壤pH上升、活性有机碳(MBC、DOC、POC和ROC)含量增加、Kos降低,土壤CO_2排放也随之增加.CaCO_3不仅能促进有机肥的矿化分解,而且它和有机肥会对土壤CO_2排放产生显著的交互效应,其效果与CaCO_3含量密切相关.低量CaCO_3和有机肥对土壤CO_2的释放具有负的表观交互效应,但高量CaCO_3和有机肥对其产生正的表观交互效应.因此,CaCO_3对土壤有机碳转化的影响不能一概而论,它与土壤中CaCO_3含量密切相关.在农业管理中,根据土壤CaCO_3含量合理施用有机肥对土壤碳素循环和温室气体(CO_2)排放都具有重要意义.

Effect of calcium carbonate content and composted manure application on soil organic carbon fractions and CO2 emissions in loessal soil

The aim of the present study was to investigate the effects of composted manure (CM) and CaCO₃ on soil CO₂ emissions. A loessal soil was amended with 0, 30 and 50 g·kg^-1of CaCO₃ to imitate all of the loessal soils with different CaCO₃ contents (9%~15%) in Shaanxi Province. Thereafter, CM was added to the soils at two rates (0 and 20 g·kg^-1), representing as L0, L30, L50, L0-M, L30-M and L50-M. The effects of above additions were investigated in an incubation experiment over a 105 d period. Soil pH, MBC, DOC, POC, ROC, Kos and CO₂ emissions were determined. The results showed that soil pH and MBC content increased with CaCO₃ content without CM application, but the difference in CaCO₃ content had no significant effect on DOC, POC, ROC, Kos and CO₂ emissions. However, soil pH, MBC, DOC, POC and ROC contents increased but Kos decreased with CaCO₃ content after CM being applied. Thus, soil CO₂ emissions increased with CaCO₃ content. In loessal soil, CaCO₃ not only promoted the mineralization of CM, but also showed a significant interaction between CM and CaCO₃ on soil CO₂ emissions. The interaction between low CaCO₃ and CM was negative, but a positive interaction was found between high CaCO₃ and CM. Therefore, we concluded that the effect of CaCO₃ on the transformation of organic C in the soil cannot be generalized; which is closely related to the CaCO₃ content in the soil. In the agricultural management, the application of CM reasonably according to CaCO₃ content in the soil will play a significant role in soil C cycling and greenhouse gas (CO₂) emissions.