轮作对黑土团聚体有机质光谱特征的影响

Effects of Crop Rotation on Spectrum Characteristics of Organic Matter in Mollisol Aggregates

为研究作物轮作对黑土各粒级团聚体碳氮含量及红外光谱结构特征的影响,选取中国科学院海伦农业生态试验站长期定位试验中大豆连作（SC）、大豆轮作（当季为大豆,SR）、玉米连作（MC）、玉米轮作（当季为玉米,MR）下的土壤为样品,用湿筛法得到大团聚体（〉0.25mm）、微团聚体（0.25～0.05mm）和粉黏粒（〈0.05mm）3个粒级,并测定其碳、氮含量和红外光谱。结果表明,土壤中以大团聚体为主。轮作对各粒级团聚体含量没有影响,轮作下原土、大团聚体和微团聚体的碳、氮含量高于连作,且玉米轮作与玉米连作之间差异显著;3个粒级团聚体碳氮含量差异显著,且微团聚体中含量最高。轮作和连作下3个粒级团聚体中官能团类型一样,含量大小均为多糖中的C—O和无机物中的Si—O〉碳水化合物的—OH或—NH〉芳香族C=C〉自由—OH〉脂肪族C—H,且轮作下脂肪族、芳香族和含烷氧结构的物质高于连作,在微团聚体中表现明显,表明轮作能促进土壤稳定性结构形成,增加稳定性物质含量,有利于碳氮固定于微团聚体中,稳定并增加土壤有机质。

For the purpose of studying the influence of crop rotation on the carbon and nitrogen content and structure characteristics of infrared spectrum in mollisol aggregates,soils were sampled from fields with soybean continuous cropping system,soybean rotation system,maize continuous cropping system,and maize rotation system in a long-term located experiment in Hailun Agricultural Ecology Testing Station of Chinese Academy of Sciences.Through wet sieving method,macro-aggregate（〉0.25 mm）,micro-aggregate（0.25—0.05mm）and silt clay（〈0.05mm）were gotten,followed by the determination of their carbon and nitrogen content,and infrared spectral structure.The results suggested that macro-aggregate was the main composition in mollisol,and crop rotation had no influence on the contents of all aggregates.Carbon and nitrogen contents in raw soil,macroaggregates and micro-aggregates under crop rotation system were higher than those under continuous planting system.Moreover,there were significant differences between continuous planting system and rotation system of maize.The carbon and nitrogen contents significantly differed among aggregates,with the highest contents in microaggregate.Under the continuous planting and rotation of crops,there were the same types of functional group in 3types of aggregates,and their contents were listed as the following：C—O in polysaccharides and Si—O in inorganic matter〉—OH and —NH in carbohydrates〉C=C in aromatic compounds〉free—OH〉C—H in aliphatic compounds.Under the rotation system,the contents of aliphatic compounds,aromatic compounds and compounds containing O-alkyl were higher than those under continuous planting system,which were especially obvious in micro-aggregate.This study indicated that crop rotation could increase the contents ofstable substance,promote the formation of soil organic matter stable structure,and benefit the existence of carbon and nitrogen in micro-aggregate so as to stabilize and increase soil organic matter.