长期施用化肥和有机肥下潮土干团聚体有机氮组分特征

Characteristics of the Fraction of Organic Nitrogen in Fluvo-aquic Soil Aggregates under Long-term Application of Chemical Fertilizer and Organic Manure

依托中国科学院封丘农业生态实验站长期施肥试验,选取不施肥(CK)、单施化肥(NPK)、有机无机肥配施(1/2OM)、有机肥(OM)处理,对比研究27a连续施用化肥和有机肥对土壤机械稳定性团聚体及其有机氮组分的影响。结果表明,长期施用有机肥显著提高了耕层土壤中大于2 mm团聚体的比例,较CK提高了33%,较NPK增加了17%。施肥显著提高耕层团聚体中有机氮含量,以OM处理效果最明显,大于2 mm、2～0.25 mm、小于0.25 mm团聚体中酸解有机氮含量分别为776.4、837.7、625.3 mg·kg^(-1)。各团聚体中有机氮以酸解铵态氮为主,氨基糖态氮最少。长期单施化肥主要提高了大于2 mm团聚体中酸解铵态氮比例,施用有机肥提高了氨基酸态氮和酸解未知态氮含量及分配比例。长期施用有机肥使潮土结构明显改善,有利于耕层团聚体中全氮及有机氮各组分的积累,氨基酸态氮、氨基糖态氮、非酸解有机氮主要赋存于2～0.25 mm团聚体中,而酸解铵态氮和酸解未知态氮在大于2 mm团聚体中分布较多,有效地提高了土壤供氮能力。

【Objective】 The objective of this research was to investigate effects of long-term fertilization on formation of soil aggregates and the fraction of soil organic nitrogen therein in fluvo-aquic soil in the North China Plain, and consequently nitrogen supplying capacity of the soil and its mechanism.【Method】 Undisturbed soil samples were collected from the four treatments, i.e. CK (no fertilization), NPK (Application of chemical fertilizers only), 1/2OM (Application of half the rate of chemical fertilizer in Treatment NPK and half of the rate of organic manure in Treatment OM) and OM (Application of organic manure only) of the long-term (27 years) fertilization experiment at the State Agro-Ecological Experimental Station in Fengqiu, for analysis of contents of mechanically-stable soil aggregates and organic nitrogen therein, with the dry-sieving method and the Bremner method, separately. 【Result】 Results show that application of organic compost increased the proportion of > 2 mm aggregates in the topsoil, significantly or by 33% and 17% as compared with CK and NPK, whereas it decreased the content of <0.25 mm aggregates. Long-term fertilization significantly increased the content of organic nitrogen in aggregates in the fluvo-aquic soil, especially Treatment OM. The content of organic nitrogen in aggregates >2 mm, 2~0.25 mm and <0.25 mm was 776.4 mg·kg^-1, 837.7 mg·kg^-1 and 625.3 mg·kg^-1, respectively. The organic nitrogen in soil aggregates was dominated with acidolyzable ammonium N, which was followed by amino acid nitrogen and unknown-acidolyzable nitrogen, aminosaccharide nitrogen, the least. Treatment NPK increased the proportion of acidolyzable nitrogen in > 2mm aggregates, while Treatment OM did the content and proportion of amino acid nitrogen and unknown acidolyzable nitrogen. 【Conclusion】 long-term application of organic manure can improve the soil structure of fluvo-aquic soil significantly, and stimulate accumulation of total nitrogen and all fractions of organic nitrogen, with amino acid nitrogen, amico sugar nitrogen and non-acidolyzable organic nitrogen accumulated mainly in 2~0.25 mm, and acidolyzable and unknown acidolyzable nitrogen in >2 mm aggregates, thus significantly increasing nitrogen supplying capacity of the soil.