长期不同施肥模式对潮土有机碳组分的影响

采用物理分组方法分析了长期不同施肥模式条件下潮土有机碳组分变化及其分布规律。结果表明，与不施肥（CK）比较，长期氮、磷、钾平衡施用（NPK）、秸秆还田（NPKS）和有机无机肥配施（NPKM和1.5NPKM）均显著提高了潮土粗自由颗粒有机碳（cfPOC）、微团聚体内物理保护颗粒有机碳（iPOC）及矿物结合有机碳（mSOC）的含量，其中以粗自由颗粒有机碳增幅最高，达114.5%～278.9％，对施肥最敏感，能较好反映长期施肥下土壤有机碳库的变化。矿物结合有机碳是潮土固存有机碳的主要形式，它占总有机碳的67.0%～80.4%。除偏施化肥（N和NP）外，其它施肥模式增加的总有机碳有49.1%～58.1%进入矿物结合有机碳组分；26.2%～31.7%进入粗、细自由颗粒有机碳组分；15.7%～20.9%进入物理保护有机碳组分。偏施化肥（N和NP）有利于自由颗粒有机碳的增加。综上分析，长期有机无机肥配施或秸秆还田是提升潮土不同组分有机碳库的较好施肥模式。

Effects of the different long-term fertilizations on fractions of organic carbon in fluvo-aquic soil

The density fractionation scheme was used to study the changes of organic carbon fractions and their distribu-tion in fluvo-aquic soil under different long-term fertilizations. The results showed that compared to no fertilization (CK), contents of coarse free particulate organic carbon (cfPOC), physical protected intra-microaggregate particulate organic carbon (iPOC) and mineral-associated soil organic carbon(mSOC) were all increased significantly under the balanced chemical fertilization(NPK), straws plus with chemical fertilization (NPKS), and manure added with chemical fertiliza-tion (NPKM and 1.5NPKM). The cfPOC fraction with the highest magnitude of increased by 114.5%-278.9% indi-cates it was more sensitive to the fertilizations than other organic carbon fractions. The mSOC, accounting for 67.0% to 80.4% of total organic carbon (TOC), was main form for organic carbon sequestration in fluvo-aquic soil. Application of unbalanced chemical fertilization (N and NP) was apt to increase free POC content, and for other fertilizations, about 49.1% -58.1% of TOC was transferred to mSOC, 26.2% -31.7% to free POC and 15.7% -20.9% to iPOC. It could be concluded that long-term manure application with chemical fertilizers or straw incorporation to soil was more ben-efit to organic carbon pools upgrade in fluvo-aquic soil.