有机无机肥长期施用对潮土团聚体及其有机碳含量的影响

Effects of Long-term Application of Organic Manure and Chemical Fertilizers on Organic Carbon in Aggregates of a Sandy Loam

用湿筛法和密度分级相结合的方法,将土壤区分为不同粒径团聚体,并进一步把团聚体细分成不同组分,系统比较了有机无机肥长期施用对潮土及其团聚体中有机C含量的影响。结果表明,潮土团聚体以53～250μm为主,有机肥长期施用显著提高了250～2000μm团聚体数量,降低了53～250μm团聚体的比例。无机肥施用增加了各粒径团聚体有机C含量,但没有改变团聚体的比例。团聚体中有机C以细颗粒有机C(fine iPOM)为主,有机肥施用显著增加了矿物态有机C含量,并通过增加250～2000μm团聚体中细颗粒有机C(fine iPOM)和矿物态有机C比例来提高土壤有机C含量。无机肥则通过比较均匀地增加团聚体中各组分有机C含量来提高土壤有机C水平。因此,有机肥和无机肥在潮土上增加土壤有机质含量的机制存在明显差异。

To evaluate the effects of long-term application of organic manure and chemical fertilizers on the concentration of soil organic matter,fluvo-aquic soils collected in the North China plain were separated into different size aggregates by wet sieving and the particulate organic matter of them were further segregated through combining density fractionation,dispersion and wet-sieving.The water-stable aggregates were dominated by the size fraction of 53 – 250 μm in the tested soil.Organic manure addition significantly increased the size fraction of 250 – 2 000 μm,but lowered the proportion of the fraction of 53 – 250 μm.The application of chemical fertilizers increased soil organic C concentrations in aggregates but did not change ratio of aggregates in soils.Soil organic carbon in aggregates mainly existed as fine particulate organic matter.Application of organic manure sharply increased concentrations of mineral-combined organic C and the proportion of fine particulate organic matter and mineral-combined organic matter.In contrast,Chemical fertilizer amendment nearly evenly increased organic carbon concentrations in different fractions of aggregates.