中文摘要：

以黄土高原南部地区的长期肥料定位试验为研究对象，通过室内测定及培养试验研究了不施肥（CK）、撂荒（FA）、施氮磷钾肥（NPK）、氮磷钾配施有机肥（MNPK）和氮磷钾配施秸秆（SNPK）培肥处理土壤中溶解性有机碳（DOC）的含量、结构特性及其降解特性。结果表明，在0～20cm耕层土壤中，不同培肥处理土壤巾DOC的含量变化范围在4．65～8．94mgkg^-1之间，平均为6．42mgkg^-1，各培肥处理间差异明显，其大小顺序为MNPK〉SNPK〉NPK〉FA〉CK。由DOC溶液的UV280吸收值和腐殖化指数（HIXem）可以得出，不同培肥处理土壤中溶解性有机物中结构相对复杂的芳香化合物所占的比例明显不同，其大小顺序为SNPK〉MNPK〉FA〉NPK〉CK。经过7d的生物降解培养，不同培肥处理土壤DOC溶液的降解率变化范围在19．3％～48．5％之间，平均为28．6％，其大小顺序为CK〉FA〉NPK〉SNPK〉MNPK。随着培养的进行，DOC溶液中结构较为复杂的溶解性有机物的比例上升。

英文摘要：

The long-term fertilization experiments located at the south edges of the Loess Plateau were used to study effects of different fertilizer treatments, i. e., no fertilizer（CK） , fallow （FA）, NPK fertilizer （NPK） , NPK ＋ organic manure（MNPK） , and NPK ＋ straw（SNPK） , on content, structural characteristics and biodegradation of dissolved organic carbon（DOC） in the soil. The contents of DOC in the surface layers （0 - 20cm in depth） of soils different in fertilization treatment ranged from 4.65 to 8.94 mg kg^-1 , and averaged 6.42 mg kg^-1. The fertilization treatments followed the order of MNPK 〉 SNPK 〉 NPK 〉 FA 〉 CK. The special absorption value at 280 nm （UV280） and the humification index （HIXem） of DOC solution indicated that significant differences existed between soils different in treatment in structural characteristics of DOC, and in terms of proportion of complex aromatic compounds in the soil, the five treatments followed the order of SNPK 〉 MNPK 〉 FA 〉 NPK 〉 CK. After 7 days of biodegradation incubation, the biodegradation rates in the treatments ranged from 19.32% to 48.49% , and averaged 28.58% , and the treatments followed the order of CK 〉 FA 〉 NPK 〉 SNPK 〉 MNPK. The UV280 and HIXem of DOC solution before and after biodegradation indicated that the proportion of dissolved organic matter more complex in structure increased with the duration of incubation.