长期施肥对绿洲农田土壤剖面有机碳及其组分的影响

Long-term effect of fertilization application on soil organic carbon and its fractions in soil profiles of an oasis farmland

以中国科学院阜康荒漠生态站长期定位试验为平台，对不同施肥模式下绿洲农田土壤有机碳（SOC）、颗粒有机碳（POC）、轻组有机碳（LFOC）及团聚体结合碳的剖面（0～3m）特征进行了研究。结果表明：与荒漠土壤相比，20a长期施肥模式下SOC含量在表层（0～0．2m）土壤中增加了14％～56％，但在下层（0．2～0．6m）减少了15％～33％。在深层（0．6～3m），单施化肥（NPK与N2P2K）与化肥配施秸秆处理（NPKR与N2P2R2）具有不同的变化：SOC含量在前者中降低了5％～9％，在后者中增加了4％～9％，POC与LFOC具有相似变化趋势。所有处理均增加了整个剖面的大团聚体（〉0．25mm）结合碳。然而，44％～87％的SOC分布于粉砂与粘粒组分（〈0．053mm）中，在深层土壤中该比例最大（超过80％），揭示了该组分中SOC含量的维持对于碳固定的重要性。单施化肥处理降低了粉砂与粘粒组分中SOC含量，可能是其深层土壤碳损耗的一个机制。化肥配施秸秆处理在促进SOC含量的增加、大团聚体形成方面具有最好效果，尤其在深层土壤。

An investigation was conducted to determine soil profile （0-3 m）changes in SOC, particulate organic carbon （POC）, light fraction organic carbon （LFOC）, and aggregate-associated carbon in a long-term field experi- ment site in an oasis farmland of the National Field Research Station of Desert Ecosystem in Fukang, Chinese Acade- my of Sciences. The following treatments were compared with the desert soil from which the oasis was created： inor- ganic fertilizer alone （NPK and N2P2K）, inorganic fertilizer combined with wheat straw（NPKR and N2P2R2）, and no fertilization（CK）. The result showed as follows： the SOC contents increased by 14%-56% in the topsoil（0-0.2 m）, but decreased by 15%-33% in the subsoil（0.2-0.6 m）under all fertilizer applications of 〉20 years. In the deep layer （0.6-3 m） there were significant differences between the treatments with and without straw： SOC decreased by 5%-9% in treatments without straw, but increased by 4%-9% in treatments with straw. POC and LFOC also had the similar trends. All treatments increased the proportion of macro-aggregates （ 〉0.25 mm） and its associated carbon throughout the soil profile. However, 44%-87% of total SOC was stored in silt＋clay fraction, especially in the deep layer. This indicated the importance of SOC stabilization in silt＋clay fraction for carbon sequestration. Application of inorganic fertilizer alone led to a significant decrease of SOC content in silt＋clay fraction in the deep layer; this should be the main mechanism for SOC loss. Combined application of inorganic fertilizer and straw had the greatest effects on increasing SOC content and enhancing the formation of macro-aggregates, especially for the deep layer.