长期施肥对棕壤有机碳组分的影响

对起始于1979年的棕壤长期肥料定位试验田2005年的耕层土壤不同有机碳组分进行了测定与分析，以探讨长期施肥影响土壤有机碳的过程及机理。结果显示:长期单施化肥降低了土壤的游离态颗粒有机碳（FPOM-C）含量，但进一步稳定了矿物结合态有机碳(MOM-C)，最终提高了土壤总有机碳(TOC)含量；长期施用有机肥和有机肥配施化肥使土壤的FPOM-C、闭蓄态颗粒有机碳(OPOC)、MOM-C以及含量均显著提高，且增加效果好于单施化肥。从各组分有机碳所占比例或相对比值来看，长期施用有机肥和有机肥配施化肥提高了POM-C/TOC比例而降低了MOM-C/TOC比例，使FPOM-C/OPOM-C比值显著增大。表明土壤有机碳结构分组的应用有助于揭示长期施肥影响土壤有机碳的机理。

Effect of long-term fertilization on organic carbon fractions in a brown soil

In order to better understand the underlying process and mechanism of long-term fertilizations influencing SOC, the topsoil total organic carbon and its physically divided forms in a long-term located fertilizer experiment were quantified. The results indicated that long-term application of chemical fertilizer alone decreased soil FPOM-C content, but stabilized MOM-C, and increased soil TOC content. Long-term application of manure alone or combined with chemical fertilizer had more significant effect on increasing soil FPOM-C, OPOM-C, MOM-C and TOC content than chemical fertilizer application alone. As far as the proportion or ratio among the various SOC fractions studied was concerned, long- term application of manure alone or combined with chemical fertilizer increased POM-C/TOC and FPOM-C/OPOM-C, and decreased MOM-C/TOC. According to our analysis and discussion, the organic C fractionation by soil structure contributed to reveal the mechanism of long-term fertilizations affecting SOC.