不同碳饱和水平下典型农田土壤有机质的红外光谱特征

The Soil Infrared Spectral Characteristics of Soil Organic Matter under Different Carbon Saturation Levels

【目的】比较长期施肥定位站点的土壤有机质红外光谱,旨在探究不同碳饱和程度下土壤有机质光谱特征。【方法】基于进贤红壤和原阳潮土长期定位试验站典型施肥处理,利用碳饱和公式计算两个站点不同处理的碳饱和水平,通过傅里叶红外光谱测定不同处理的土壤有机质官能团特征,分析不同站点不同处理间有机碳饱和特征及光谱特征。【结果】原阳潮土的土壤有机碳年变化率与碳投入之间呈线性关系,但进贤红壤则呈"曲线"关系。进贤红壤的碳饱和亏缺度(saturation deficit,SD)为0.118—0.413,显著小于原阳潮土的0.462—0.616。进贤红壤和原阳潮土的处理中含有相同的官能团:芳香类碳(1 636 cm^(-1),695 cm^(-1)),脂肪族碳(3 000—2 850 cm^(-1),1 455 cm^(-1)),碳水化合物或多糖类(1 080 cm^(-1),1 033 cm^(-1)或1 034 cm^(-1)),有机态硅类(1 100—1 008 cm^(-1),526cm^(-1),795 cm^(-1),778 cm^(-1),470 cm^(-1))。进贤红壤的芳香族、脂肪族和硅类特征峰的吸收强度明显高于原阳潮土的偏施肥处理;而原阳潮土偏施肥和有机肥处理的羧基类、烷烃类和碳水化合物类特征峰的吸收强度明显高于进贤红壤有机肥处理。综合分析两个站点各处理,土壤有机碳含量与透光率之间呈显著负相关关系。相对于原阳潮土,进贤红壤各处理碳投入、土壤黏粒含量和铁铝氧化物含量均较高,且进贤为水田双季稻轮作制度,水分管理措施更有利于土壤有机碳的累积。【结论】综合两站点的土壤有机碳年变化率与碳投入关系以及碳亏缺度显示进贤红壤有机碳已经趋于饱和,而原阳潮土则还距碳饱和较远。两站点的红外光谱特征表明进贤红壤以芳香族、脂肪族和硅类等难分解惰性官能团为主,而原阳潮土则以羧基类、烷烃类和碳水化合物类易分解官能团为主。红外光谱透光率水平可以半定量土壤有机质官能团。

【Objective】The objective of this study is to explore the infrared spectra characteristics of soil organic carbon(SOC)with different SOC saturation levels under different long-term fertilization.【Method】Based on two long-term experiments at Jinxian(Red soil with double rice cropping)and Yuanyang(Fluvo-aquic soil with winter wheat-summer maize cropping)sites,the typical fertilizer treatments were selected.The saturation deficit(SD)under different treatments was calculated and analyzed.The different functional groups were measured by Fourier transform infrared spectroscopy(FTIR),and then the characteristics among different treatments were analyzed.【Result】It was linear relationship between SOC annual change rate and C input at Yuanyang,while the asymptotic line at Jinxian.The SD value at Jinxian(0.118-0.413)was obviously smaller than that at Yuanyang(0.462-0.616).The similar functional groups such as aromatic(1 636 cm^-1,695 cm^-1),aliphatic(3 000-2 850 cm^-1,1 455 cm^-1),carbohydrate/polysaccharides(1 080 cm^-1,1 033cm^-1/1 034 cm^-1)and organosilicone(1 100-1 008 cm^-1,526 cm^-1,795 cm^-1,778 cm^-1,470 cm^-1)were both at Jinxian and Yuanyang sites.The absorption intensity of aromatic,aliphatic and organosilicone series was clearly stronger at Jinxian than that at Yuanyang,while the absorption intensity of carboxyl,alkane and carbohydrate was stronger at Yuanyang than that at Jinxian.The SOC content was negatively correlated with light transmittance.Compared with Yuanyang,the carbon input,clay content and iron-aluminum oxides were higher in Jinxian.Furthermore,the water regime with double rice at Jinxian was more benefit for SOC accumulation.【Conclusion】The results of the relationship between SOC change rate and C input and the SD value indicated that the higher saturation level appeared at Jinxian site.There were more recalcitrant components like aromatics,aliphatic and organosilicone at Jinxian,while the labile component like carboxyl,alkanes and carbohydrate appeared at Yuanyang.The infrared transmittance could quantify the function group to some extent.