长期不同施肥对塿土大团聚体中有机碳组分特征的影响

【目的】研究长期施肥对土大团聚体中有机碳组分特征的影响,揭示不同施肥方式下土壤有机碳的固持机制,为合理施肥提供理论依据。【方法】采集土35年长期肥料定位试验不同施肥处理0—10 cm和10—20 cm土样,分析其大团聚体中各组分有机碳含量的变化。试验处理为:不施肥(CK)、单施化肥(NP)、单施有机肥(M)和有机肥配施化肥(MNP)。【结果】与CK相比,长期NP处理对大团聚体中粗颗粒有机碳(cPOC)、细颗粒有机碳(fPOC)、大团聚体中微团聚体内颗粒有机碳(iPOC)以及矿质结合态有机碳(MOC)组分的有机碳(OC)含量均无显著影响;而M处理以及MNP处理可显著提高两土层cPOC和iPOC组分的OC含量以及0—10 cm土层MOC组分的OC含量,其中,cPOC含量增幅分别为174%~338%和215%~245%,iPOC含量增幅分别为127%~241%和106%~130%,MOC含量增幅达28.9%~34.6%。MNP处理显著提高了0—10 cm土层fPOC组分的OC含量,增幅达482.1%。累积碳投入量与大团聚体中各组分的OC含量呈显著线性相关,尤其是iPOC含量,表明长期施肥过程中土有机碳在大团聚体中固存的差异主要受物理保护的颗粒有机碳组分的影响。【结论】关中地区土长期施化肥对大团聚体中各组分OC含量没有显著影响,而长期单施有机肥能进一步增加大团聚体中各组分OC含量,有机肥配施化肥能显著增加团聚体中各组分OC含量,特别是大团聚体中微团聚体内颗粒有机碳组分的含量,进而增加土的有机碳固持。因此,有机肥配施化肥是提高土有机碳含量的有效措施。

Effects of long-term different fertilizations on organic carbon fractions of macroaggregates in Anthrosol

ObjectivesTo characterize organic carbon fractions within macroaggregates in arable soils and understand mechanisms of soil organic carbon sequestration and optimize the fertilizer management.MethodsSoil samples were collected from 0–10 cm and 10–20 cm layers of a 35-year long term fertilizer experiment in an Anthrosol in Yangling, Shaanxi Province, and organic carbon (OC) contents were analyzed within the macroaggregate size fractions (coarse particulate organic carbon referred to as cPOC, fine particulate organic carbon referred to as fPOC, intra-microaggregate particulate organic carbon referred to as iPOC and mineral associated organic carbon referred to as MOC). The fertilization treatments were 1) Control, receiving no fertilizers; 2) NP, receiving chemical nitrogen and phosphorus fertilizers; 3) M, receiving organic manure alone, and 4) MNP, receiving the combined application of chemical NP fertilizers and organic manure at the same rates as treatments NP and MNP. ResultsThe long-term application of chemical fertilizers (NP) had no effects on the OC contents of any macroaggregate size fractions. However, application of manure alone or combined with chemical fertilizers greatly enhanced cPOC contents by 174%–338% (0–10 cm) and 215%–245% (10–20 cm), iPOC content by 127%–241% (0–10 cm) and 106%–130% (10–20 cm), and MOC content by 28.9%–34.6% in the 0–10 cm soil layer. Moreover, application of manure plus NP significantly increased fPOC content in the 0–10 cm layer by 482%. In addition, OC contents of all macroaggreagte fractions were significantly and positively correlated with cumulative C input, especially for the iPOC content. These results indicated that the differences among fertilization regimes in OC sequestration occurred primarily in the physically protected OC fractions contained in macroaggregates. ConclusionsApplication of NP showed no effect on OC contents within macroaggregates, while application of M treatment could increase OC contents within macroaggregates, and MNP treatment significantly enhanced OC contents within macroaggregates, especially for iPOC content. Amendment of organic manure, alone or in combination with chemical fertilizers, could increase soil organic carbon (SOC) storage. Our data indicated that the combination of organic and chemical fertilizer is the most effective practice for increasing SOC storage in an Anthrosol.