三种南方典型水稻土长期试验下有机碳积累机制研究Ⅲ.两种水稻土颗粒有机质结构特征的变化

采用固体交叉极化魔角自旋¹³C核磁共振(CPMAS¹³C-NMR)波谱技术对长期不同施肥处理下红壤性水稻土和太湖地区黄泥土本体土壤以及水稳性团聚体中颗粒有机质（POM）的化学结构特征进行了研究。结果表明,不同施肥处理下本体土壤和不同粒径水稳性团聚体中POM的结构组成相似,主要由烷氧C、烷基C和芳香C组成,其中以烷氧C含量最高。施肥改变了本体土壤POM中各类C原子的相对百分含量,有机肥以及化肥配施有机肥条件下烷氧C含量明显降低,芳香C和酚基C含量有不同程度的增加,表明POM的稳定性增强;单施化肥下烷氧C含量最高,而烷基C、芳香C和芳香度均最低,POM的稳定性减弱,不利于POM的积累。施肥改变了黄泥土不同粒径水稳性团聚体中POM各类C原子的相对百分含量,从而使得不同粒径中POM对其团聚体的稳定性作用发生变化;而红壤性水稻土不同粒径水稳性团聚体POM各类C原子的相对百分含量并未明显受到施肥措施的影响。

SOC ENHANCEMENT IN THREE MAJOR TYPES OF PADDY SOILS IN A LONG-TERM AGRO-ECOSYSTEM EXPERIMENT IN SOUTH CHINA Ⅲ. STRUCTURAL VARIATION OF PARTICULATE ORGA

Particulate organic matter (POM) structures of both bulk soil and size fractions of water-stable aggregates from a typical hydroagric paddy soil from Tai Lake region, Jiangsu Province, and a red earth-derived paddy soil in Jiangxi Province, China under long-term different fertilization trials were studied by CPMAS¹³C-NMR spectroscopy. Little variation was found of the composition of C species with size fractions, with the soil types and with the fertilization treatments as POM in both bulk soil and water-stable aggregates. Both soils were composed basically of O-alkyl-C, Alkyl-C and Aromatic-C, with the former being dominating. However, different fertilization treatments modified the proportion of different carbon species of the POM from the bulk samples as the portion of O-alkyl-C was decreased and that of aromatic-C and phenolic-C increased under both organic fertilization and compound fertilization of organic and inorganic fertilizers, indicating the enhanced chemical stability of POM under organic amendments; Whereas, increased portion of O-alkyl-C but decreased portion of alkyl-C, aromatic-C and aromaticity was observed under chemical fertilization only, indicating a more readily decomposable nature. The relative proportion of each C species also differed in water-stable aggregates of the size fractions from both soils and long-term different fertilization treatments, and it modified the interactive effect of POM and water-stable aggregates of the paddy soils, which is less significant for the red earth-derived paddy soil.