不同有机厩肥输入量对土壤团聚体有机碳组分的影响

土壤是重要的有机碳库,其微小变化可能引起大气CO2浓度水平的较大变异。土壤团聚体对土壤有机碳具有物理保护作用。有机厩肥的输入既可以提高土壤有机碳含量,又可以促进土壤团聚体的形成,对土壤有机碳的截获和保持有重要意义。本实验采用湿筛的方法分离土壤团聚体,并对团聚体进行有机碳组分分离。通过对连续8年施加不同量有机厩肥试验的研究发现:适量的有机厩肥施用可以显著地提高土壤的平均质量直径(MWD),改善土壤结构;过量施用有机厩肥则明显降低了>2 000μm团聚体含量。潮棕壤有机碳主要分布在250～53μm和2 000～250μm团聚体中,两者相加约占有机碳全量的73.7%～78.5%。并且随着有机碳输入量的增加,土壤有机碳主要贮存在2 000～250μm团聚体中。有机厩肥的施加明显地加快了>2 000μm团聚体的更新速率。土壤轻组分有机碳含量也随有机厩肥输入量的增加而不断增加,高量有机厩肥下占全量的22.1%。土壤固定有机碳的能力有限,存在明显的等级饱和现象。因此,在有机质匮乏的土壤施用有机肥意义重大,应尽量减少向高有机质土壤输入有机碳。

Effect of application rate of barnyard manure on organic carbon fraction of soil aggregates

Soil is an important organic carbon pool, of which any small change may lead to great variation of CO2 concentration in the atmosphere. Soil aggregates have the function of physical protection of soil organic carbon. Application of barnyard manure can not only increase the content of soil organic carbon, but also promote formation of soil aggregates, which is of great significance to sequestrating and maintaining soil organic carbon. In this experiment the wet sieving method was used to isolate and fractionate aggregates. It was found after a 8-year stationary field experiment on application rate of manure that application of an appropriate amount of manure significantly increased soil mean weight diameter (MWD), and improved soil structure, but excessive application of manure significantly reduced the content of >2 000 µm aggregates while increased that of 2 000~250 µm aggregates. In Aquic-brown soil, soil organic carbon was mainly distributed in 250~53 µm and 2 000~250 µm fractions of aggregates, accounting for about 73.7%~78.5% of the total soil organic carbon content. With increased input of organic carbon, soil organic carbon was mainly stored in the 2 000~250 µm fraction of aggregates. Manure application significantly sped up renewal of the >2 000 µm fraction of aggregates. The content of light fraction organic carbon in the soil increased with increased manure input, and accounted for 22.1% of the total soil organic carbon in the soil applied with a high rate of manure. The ability of the soil to sequestrate organic carbon is limited, and apparent phenomena of hierarchical saturation are observed. It is, therefore, concluded that in soils deficient in organic matter, it is of great significance to apply organic manure, whereas in soils high in organic matter it is advisable to put in less organic carbon.