关键词: 长期施肥, 黑土, 水稳性团聚体, 有机碳含量, 有机碳贡献率

Abstract:

【Objective】Based on the long-term fertilization experiment station, in aims to study the influences on the soil fertility by long-term application of chemical fertilizer and manure, the characteristics of water stable aggregates and structure of organic carbon was analyzed under different fertilizer application conditions.【Method】0-20 cm soil samples were collected from the 37-year long-term field experiment, including six treatments: CK (no fertilizer), NPK (chemical fertilizer alone), M₂ (normal manure application), M₂NPK (the chemical fertilizer combined with normal manure rate), M₄ (high quantity manure application), and M₄NPK (the chemical fertilizer combined with high quantity manure rate). Stability of water stable aggregates and distribution of organic carbon in aggregates were analyzed by wet sieve method.【Result】The proportion of large aggregates was reduced,while the proportion of micro aggregates was increased significantly under long-term application of organic and chemical fertilizer and high amount of organic fertilizer conditions. There was not significant change for the distribution of aggregates under long-term application of chemical fertilizer and constant organic fertilizer conditions. Compared with CK, the proportions in macro-aggregate of M₂NPK, M₄NPK and M₄ were reduced by 32.7%, 45.8% and 55.4%, respectively, and the proportion of that in micro-aggregate were increased by 73.2%, 102.5% and 123.9%, respectively. The stability of surface soil water stable aggregates was reduced significantly under long-term organic combined chemical fertilizer and high amount of organic fertilizer conditions. The soil organic carbon content was increased significantly by 1.12-2.06 times as much as CK under long-term fertilization condition, and the increase of organic carbon content was more significantly in organic fertilizer and organic combined with chemical fertilizer. The content of organic carbon in soil water stable aggregates of each size was increased under long-term organic fertilizer application, while the increase of organic carbon content in each treatment was gradually decreased with the decrease of particle size. Organic carbon content in the water stable macro-aggregate was significantly higher than that in the micro-aggregate, indicating that the organic carbon was mainly distributed in the macro-aggregate. The contribution rate of organic carbon in macro-aggregate was reduced significantly, and the contribution rate of organic carbon was increased significantly in micro-aggregate under long-term application of high amount of organic and combined with chemical fertilizer. The contribution rate of organic carbon in other treatments was higher in macro-aggregates than in micro-aggregates.【Conclusion】There were no significant effect for distribution and organic carbon content in aggregates under long-term chemical fertilization. The proportion of macro-aggregates and the stability of soil aggregates were reduced significantly under high amount of organic fertilizer and combination of organic and chemical fertilizer. The content of organic carbon in the aggregates was increased significantly under long-term application of organic fertilizer. The contribution rate of organic carbon in macro-aggregates was reduced significantly under high amount of organic fertilizer and combined with chemical fertilizer. The micro-aggregate was the dominant aggregate size of the organic carbon contribution rate.

Key words: long-term fertilization, black soil, water stable aggregates, content of organic carbon, contribution rate of organic carbon