免耕条件下不同秸秆覆盖量的土壤有机碳红外光谱特征

【目的】研究不同秸秆覆盖量免耕条件下不同剖面深度土壤的红外光谱特征，探讨免耕对土壤有机碳组成的影响及秸秆来源土壤有机碳在不同土层的分布特征。【方法】以吉林省梨树县黑土秸秆覆盖免耕长期定位试验区不同层次土壤为研究对象，对比分析无秸秆覆盖（CK）、33%秸秆覆盖、67%秸秆覆盖、100%秸秆覆盖4种处理土壤红外光谱特征。【结果】连续5年秸秆覆盖免耕种植后的土壤，红外光谱吸光值随着剖面层次的加深而降低；差减土壤矿物光谱后的谱图表明：0—5 cm土层土壤红外基团吸收明显增加，芳香碳、脂肪碳、烷基碳较之下层土壤具有明显的吸收峰。【结论】秸秆覆盖有利于有机碳在表层的累积，显著增加秸秆来源的芳香碳、脂肪碳及烷基碳含量。

Effect of No-Tillage with Different Stalk Mulching on Soil Organic Carbon and Mid-Infrared Spectral Characteristics

【Objective】 The effects of no-tillage on soil organic carbon components and distribution of soil organic carbon from stalk mulching at different soil depths and the mid-infrared spectral characteristics of different stalk mulching conservation tillage at different soil depths were studied. 【Method】 Soils were sampled from different soil depths in a long-term experiment of conservation tillage carried out in Lishu, Jilin province. Four treatments were set as no-stalk mulching, 33% stalk mulching, 67% stalk mulching and 100% stalk mulching. Soil mid-infrared spectra were examined using Nicolet 6700 spectrometer with 64 scans and 4 cm-1 resolution. 【Result】 The mid-infrared absorbance decreased with the increasing soil depth in all treatments. The results of spectra subtraction, i.e. the soil (neat) spectra minus the ashed soil spectra showed that the top soil (0-5 cm) had greater absorbance at the aromatic, aliphatic and alkyl bands than deeper soil (5-20 cm). 【Conclusion】 Stalk mulching could promote soil organic carbon accumulation at 0-5 cm depths and increase significantly aromatic, aliphatic and alkyl organic carbon from straw mulching. The mid-infrared spectral characteristics provide a new tool for soil organic carbon components research.