采集不同施肥24年的红壤,采用物理分组的方法,观测了长期不同施肥下红壤有机碳及其组分变化,并结合历史资料分析了不同施肥模式对红壤有机碳及其颗粒组分的影响。结果表明,化肥配施有机肥（NPKM）处理下红壤总有机碳含量（10.33 g/kg）,砂粒（2000～53μm）、细粉粒（5～2μm）和粘粒（〈2μm）组分中的有机碳含量显著高于其他处理。与不施肥（CK）相比,施用化肥（NPK、2NPK）和有机肥（NPKM、M）显著地提高了红壤有机碳在砂粒和粘粒中的分配比例,而降低了其在粗粉粒和细粉粒的分配比例。施化肥（NPK、2NPK）、单施有机肥（M）、化肥配施有机肥（NPKM）处理,土壤有机碳的平均固定速率分别为0.05 t/（hm2·a）、0.18 t/（hm2·a）、0.26t/（hm2·a）。相关分析表明,不同施肥模式下红壤有机碳的固定量与碳投入量之间存在着极显著的线性相关关系（R2=0.909,P〈0.01）,土壤的固碳效率为8.1%;随着碳投入的增加,粗粉粒和细粉粒有机碳储量逐渐下降,而砂粒和粘粒中碳储量逐渐增加,并且粘粒增加速率要远远高于砂粒。以上结果说明,红壤中有机碳还没有达到饱和,还具有一定的固碳潜力,增加的有机碳主要固持在粘粒中,粘粒是红壤有机碳的主要固持组分。%Through collecting the red soil under 24 years different fertilization,changes in total organic carbon（SOC） and its fractions in red soil were studied by physical partial size fractionation method.The effects of various fertilizations on soil organic carbon in total soil and its particle-size fractions were analysed based on historical recorded data.Results showed that manure combined with mineral fertilization（NPKM） had the highest SOC content（10.33 g/kg） compared with other treatments.Also,organic carbon concentration in sand（2000-53 μm）,fine silt（5-2 μm）,and clay（〈2 μm） size fractions under the NPKM treatment was the highest of all treatments.Compared with the CK treatment,application of mineral NPK fertilizations（NPK,2NPK） and the organic fertilizations（M,NPKM） significantly increased the distribution proportion of organic carbon in sand and clay size fractions,whereas significantly reduced the distribution proportion in coarse-silt and fine-silt size fractions.Averaged soil carbon sequestration rate under the treatments of mineral fertilizaters（NPK,2NPK）,M and NPKM were 0.05 t/（ha·a）,0.18 t/（ha·a）,0.26 t/（ha·a）,respectively.There was a strong positive linear correlation between carbon sequestered and carbon input（R2=0.909,P〈0.01） at this site,indicating that the conversion rate of carbon input to SOC was 8.1%.With the increase in carbon inputs,the carbon storages in coarse silt and fine silt fractions decreased gradually.However,carbon storages in sand and clay increased with higher increment in clay than that in sand.We concluded that organic carbon was mainly sequestrated in clay fraction,which was the key component for soil carbon sequestration.Soil organic carbon did not reach the saturation in red soil and have the potential to sequester more carbon.
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