小麦玉米秸秆连续还田对土壤有机质红外光谱特征及氮素形态的影响

通过6年的田间定位试验,探讨了CK(不施肥,秸秆不还田)、SF(施肥,秸秆不还田)、T1(施肥,玉米秸秆还田)、T2(施肥,小麦秸秆还田)、T3(施肥,玉米小麦秸秆还田)5种处理对土壤氮素形态和有机质红外光谱特征的影响。结果显示:与SF相比较,T1、T2、T3处理使土壤有机氮含量分别增加3.7%、15.9%和18.5%,土壤无机氮含量分别减少15.5%、15.9%和24.0%,其中铵态氮分别降低11.3%、6.0%和12.0%,土壤硝态氮含量分别降低19.3%、22.9%和32.1%;与SF相比较,T1、T3处理土壤有机质(SOM)的C/N分别降低2.8%和1.4%,T2处理SOM的C/N提高1.4%;C/O分别提高9.2%、12.8%和12.1%;而H/C分别降低4.6%、5.5%和4.6%。红外图谱分析显示,T1、T2、T3处理引起3 500~3 200 cm?1处的吸收峰增加,2 924 cm?1处出现了新的弱峰,表明SOM的脂肪族特征增加,且以1 630 cm?1处为中心的宽带吸收峰强度明显增加,SOM芳构化程度增强。研究表明,施肥显著提高了土壤有机氮、无机氮含量,以及土壤有机质的C/N和C/O。而秸秆还田降低了土壤无机氮,提高了土壤有机氮,使SOM的C/N、H/C下降,C/O上升,同时提高了SOM中酚基、羟基、羧基、芳香碳和酰胺含量,其中以小麦、玉米秸秆双季还田的效果最为显著。

Effect of continuous wheat and maize straw incorporation on soil nitrogen and Fourier transform infrared spectroscopic (FTIR) characterization of soil organic matter

A 6-year field experiment was conducted to study the changes in the forms of soil nitrogen under the treatments of SF (chemical fertilizer application without straw incorporation), T1 (chemical fertilizer application with smashed maize straw incorporation), T2 (chemical fertilizer application with smashed wheat straw incorporation), T3 (chemical fertilizer application with smashed maize and wheat straws incorporation), with no fertilization and no straw incorporation (CK)as the control. Change in FTIR (Fourier transform infrared spectroscopic) characteristics of soil organic matter was also analyzed. The results showed that compared with SF, soil organic nitrogen under T1, T2 and T3 treatments increased respectively by 3.7%, 15.9% and 18.5% and soil inorganic nitrogen decreased by 15.5%, 15.9% and 24.0%. And the ammonium nitrogen content in the treatment of T1, T2, T3 decreased respectively by 11.3%, 6.0% and 12.0% and nitrate nitrogen decreased by 19.3%, 22.9% and 32.1%. The C/N ratio in SOM under T1 and T3 treatments decreased respectively by 2.8% and 1.4%, but the C/N ratio in T2 treatment increased by 1.4%, compared with those under SF treatment. And the ratio of C/O in SOM increased respectively by 9.2%, 12.8% and 12.1% and H/C ratio decreased by 4.6%, 5.5% and 4.6% under T1, T2 and T3 treatments compared with under SF. FTIR spectrum analysis showed that SOM absorption intensity in the 3 5003 200 cm1 band increased under T1, T2 and T3 treatments, with a new band at the 2 924 cm^-1 band. This suggested an increase in aliphatic compounds of SOM. The absorption intensity at the 1 630 cm^-1 band strengthened, suggesting increase in aromatic compounds content. The results verified that fertilization significantly increased the soil contents of organic and inorganic nitrogen as well as the ratios of C/N and C/O in SOM. The incorporation of crop straw residue decreased inorganic nitrogen as well as the ratios of C/N, H/C in SOM. It also increased the content of organic nitrogen and the ratio of C/O in SOM. Meanwhile, the incorporation of straw residue (under T1, T2 and T3 treatments) increased the contents of alcohols, phenols and carboxylic acids, aromatic carbon and amide groups of SOM. The incorporation of both wheat and maize straw residues had more obvious effect.