长期施肥对黑土有机碳矿化和团聚体碳分布的影响

采用我国东北地区的连续施肥28 a的典型黑土,通过颗粒分组的方法,研究了长期不同施肥处理对土壤团聚体形成和有机碳在各级团聚体中的分布规律,以及各粒级团聚体对养分的贡献能力的影响。结果表明,施用有机肥促进了土壤中大颗粒团聚体(>0.25 mm)的形成,尤其以2~1 mm粒级增加的比例最大;而当化肥和有机肥配合施用后,主要促进土壤中<1 mm团聚体形成,尤其对0.5~0.25 mm粒级团聚体形成的促进作用最大。施肥(无论是有机肥还是化肥)能增加土壤有机碳含量,而且,化肥有机肥配合施用较单施化肥和单施有机肥的效果更好。随着团聚体粒级的降低,团聚体中有机碳的分配出现两个峰值,分别在2~1 mm和0.25~0.053 mm两个粒级中出现。单施化肥处理及化肥有机肥配施处理与无肥处理相比均增加了0.5~0.25 mm粒级团聚体对有机碳的贡献率;单施有机肥的处理与无肥处理相比增加了1~0.5 mm粒级团聚体对有机碳的贡献率。然而,对于东北的典型黑土,2~1 mm和0.25~0.053 mm两个粒级对土壤有机碳的保护作用最大,表明团聚体对有机碳的保护作用是碳分配和矿化分解作用的综合结果,通过调控施肥种类可以达到有效保护土壤质量和肥力的效果。

Organic carbon mineralization and carbon contribution in aggregates as affected by long-term fertilization

Formation, distribution and contributing rates of aggregates to organic carbon in black soil in a 28-year long term fertilization experiment were explored with the physical fractionation method. Results show application of organic fertilizer promoted formation of large-sized aggregates (>0.25 mm), especially 2～1 mm fraction, while combined application of chemical and organic fertilizer did the formation of <1 mm fraction, particularly 0.5～0.25 mm fraction. Fertilization, no matter chemical or organic, increased organic carbon content in the soil, however, the effect of combined application of organic and chemical fertilizers was better than that of the application of either organic or chemical fertilizer. Distribution of organic carbon in aggregates formed two peaks, one in 2～1 mm fraction and the other in 0.25～0.053 mm fraction. In fertilization treatments, no matter organic, chemical and combined, the contribution of 0.5～0.25 mm fraction to organic carbon in the soil was greater than in CK, while application of organic fertilizer alone did more than CK the contribution of 1～0.5 mm fraction. However, in the case of the typical black soil in Northeast China, 2～1 mm and 0.25～0.053 mm fractions contributed the greatest to the protection of organic carbon in the soil, suggesting that the effect of aggregates protecting organic carbon in the soil is the result of the integration of distribution and mineralization of organic carbon. It is, therefore, feasible to effectively preserve soil qualify and fertility by choosing types of fertilizers.