长期施肥下黑土活性氮和有机氮组分变化特征

【目的】研究长期不同施肥措施下土壤活性氮和有机氮组分特征,探讨土壤活性氮和有机氮组分之间的关系,为评价土壤肥力、制定合理施肥措施提供科学依据。【方法】利用开始于1979年的哈尔滨黑土肥力长期定位试验,选取对照(CK,不施肥)、不施氮肥(PK)、单施化肥(NPK)、单施有机肥(M)、有机无机肥配施(MNPK)5个处理,采用氯化钾浸提-差减法、氯仿熏蒸-K2SO4提取法和Bremner法分别测定不同处理土壤可溶性有机氮、微生物生物量氮和有机氮组分含量。【结果】长期施用化肥对土壤耕层活性氮和有机氮组分含量无显著影响。单施有机肥和有机无机肥配施处理较单施化肥处理可溶性有机氮含量分别增加34.7%和56.2%,微生物生物量氮含量分别增加89.8%和144.7%。与单施化肥相比,长期单施有机肥和有机无机肥配施显著增加了酸解铵态氮、酸解氨基酸氮、酸解氨基糖氮和酸解未知氮的含量,增幅分别在23.3%—29.1%、19.2%—33.2%、30.6%—47.6%和20.2%—32.0%,对非酸解氮无显著影响。不同施肥措施下有机氮各形态的分布趋势为非酸解氮酸解氨基酸氮酸解铵态氮酸解未知氮酸解氨基糖氮。与单施化肥相比,长期单施有机肥和有机无机肥配合施用处理酸解有机氮占全氮比例有所提高,增幅达6.4%和9.9%。土壤全氮、可溶性有机氮、微生物生物量氮均与酸解有机氮组分之间均存在显著的正相关关系。在土壤有机氮组分中,酸解氨基酸氮、酸解未知氮和酸解铵态氮对可溶性有机氮和微生物生物量氮的影响最大。【结论】土壤氮素含量的变化与施肥措施密切相关,有机无机肥配施措施能显著增加土壤活性氮和有机氮组分含量,有利于提高土壤氮素供应能力;酸解氨基酸氮、酸解未知氮和酸解铵态氮是土壤活性氮的主要贡献因子。

Variation Characteristics of Fractions of Active Nitrogen and Organic Nitrogen Under Different Long-Term Fertilization Practices in Black Soil

【Objective】The objective of this study is to research characteristics of fractions of active nitrogen and organic nitrogen and their relationship under long-term different fertilization, and to provide a scientific basis for evaluating soil fertility and improving fertilization management and in the black soil (Typic hapludoll).【Method】A long-term experiment with various fertilizations was carried out during 1979-2014 in a rotation system with wheat (Triticum Aestivium) -soybean (Glycine max) -maize (Zea mays) in black soil of northeastern China. The experiment consisted of five treatments: non-fertilization (CK), PK fertilizer (PK), NPK fertilizer (NPK), horse manure (M), horse manure plus NPK fertilizer (MNPK). Soil soluble organic nitrogen (SON), microbial biomass nitrogen (MBN) and organic nitrogen fractions were measured by the extraction-subtraction method, fumigation-extraction method and acid hydrolysis-distillation method (Bremner method), respectively.【Result】The contents of fractions of active nitrogen and organic nitrogen were not affected by long-term application of NPK fertilizers. Compared with NPK, the contents of SON in horse manure application (M) and chemical fertilizers application combined with horse manure (MNPK) increased by 34.7% and 56.2%, while MBN increased by 89.8% and 144.7%, respectively. Compared with CK and NPK, long-term horse manure application (M and MNPK) significantly increased the contents of ammonia N (AN), amino acid N (AAN), amino sugar N (ASN) and hydrolysable unknown N (HUN) by 23.3%-29.1%, 19.2%-33.2%, 30.6%-47.6% and 20.2%-32.0%, respectively. However, the content of non-hydrolysable N (NHN) was not changed under different fertilization treatments. The contents of different forms of organic nitrogen fractions in all treatments displayed an order of NHN＞AAN＞AN＞HUN＞ASN. Compared with NPK, long-term application of M and MNPK increased the proportion of total hydrolysable N accounted for total nitrogen by 6.4% and 9.9%, respectively. A significant positive correlation between soil total nitrogen (TN), SON, MBN and acid hydrolysable organic nitrogen (AHON) fractions, and the effects of AAN, HUN and AN on both SON and MBN were the most. 【Conclusion】The changes of soil nitrogen content was closely related to fertilization measures. Long-term chemical fertilizers application combined with horse manure is an effective way for increasing various forms of nitrogen content and improving supply capacity of soil nitrogen. AAN, HUN and AN were the major contributors to the active nitrogen in black soil.