玉米秸秆覆盖还田量对免耕土壤有机碳中红外光谱特征的影响

依托位于中国东北黑土地区长期免耕玉米秸秆还田试验平台,分析了不同秸秆还田量(0、33%、67%和100%)连续归还8年后表层(0～5 cm)、中层(20～40 cm)和深层(60～100 cm)土壤有机碳中红外光谱特征,评价了玉米秸秆还田量对免耕土壤碳化学组成和稳定性的影响。结果表明: 与免耕无秸秆覆盖还田相比,33%与100%秸秆还田均有利于表层和中层多糖组分的积累,但前者降低了表层土壤碳组成多样性,而后者有利于各层次土壤碳化学稳定性的维持;67%秸秆还田提高了深层土壤碳化学稳定性。综上,当秸秆资源充足时,免耕结合100%全量秸秆还田可在提高0～40 cm土层微生物可利用碳底物的基础上,维持土壤碳的化学稳定性。秸秆还田量与土壤中红外光谱特征间无线性关联,表明亟需挖掘不同秸秆还田量处理下土壤碳周转的微生物参与机制。

Effects of corn stover mulch quantity on mid-infrared spectroscopy of soil organic carbon in a no-tillage agricultural ecosystem

We examined carbon chemical composition and stability along soil depth (topsoil 0-5 cm, mid-soil 20-40 cm, and deep soil 60-100 cm) in a no-tillage (NT) agricultural system with various amount of corn stover as mulch for 8 years, including 0 (NT₀), 33% (NT₃₃), 67% (NT₆₇) and 100% (NT₁₀₀), in Northeast China, using mid-infrared spectroscopy. The results showed that, relative to NT₀, the treatments of NT₃₃ and NT₁₀₀ increased polysaccharide content of the top layer and mid-layer soils, the former decreased topsoil carbon component diversity, while the latter maintained soil carbon stability of three soil layers. NT₆₇ increased carbon stability at the deep layer soil. Our results demonstrated that if corn stover resources were sufficient, NT with 100% corn stover mulch could both be beneficial to carbon availability at 0-40 cm soil layer and stability of the whole soil profile. The nonlinear relationship between the amount of corn stover mulch and the mid-infrared spectral characteristics of the soil called for further research on the microbial-control mechanism over soil carbon cycling under different amounts of corn stover mulch.