中文摘要：

【目的】探讨不同施肥措施土壤有机碳在不同粒级颗粒中的分配及变化情况,可揭示各级颗粒中有机碳与外源有机碳输入之间的定量关系。【方法】依托南方红壤连续20年长期定位施肥试验,依据外源有机碳累积输入梯度选择不施肥（CK）、氮磷钾化肥配施（NPK）、氮磷钾化肥与秸秆配施（NPKS）、轮作条件下氮磷钾化肥与有机肥配施（NPKMR）、氮磷钾化肥与有机肥配施（NPKM）、单施有机肥（M）、增量氮磷钾化肥与增量有机肥配施（1.5NPKM）7个处理,并采用物理分组方法将土壤颗粒分为砂粒（53-2000μm）、粗粉粒（5-53μm）、细粉粒（2-5μm）和粘粒（〈2μm）4个组分。【结果】与不施肥相比,长期施肥均能显著增加土壤总有机碳及各级颗粒中的有机碳的储量,其中以施用有机肥的效果最明显。不同施肥处理各级颗粒中以粘粒的有机碳储量最高,平均为16.26 t/hm2。施用有机肥和秸秆还田均能显著增加砂粒中有机碳的分配比例,降低粘粒有机碳的分配比例而对粗粉粒和细粉粒无显著影响。土壤砂粒所占的质量百分比及其与粗粉粒、细粉粒和粘粒的比值均与粗粉粒、细粉粒和粘粒组分中有机碳的浓度呈显著正相关关系表明小颗粒（粗粉粒、细粉粒和粘粒）中有机碳的固持和富集促进了大颗粒（砂粒）的形成与稳定。各级颗粒之间,施用有机肥处理的土壤粘粒组分的固碳速率最快,为0.29-0.52 t/（hm2·a）,其次为砂粒[0.30-0.40 t/（hm2·a）]而粗粉粒和细粉粒的固碳速率基本相当为0.09-0.16t/（hm2·a）。分析结果还表明土壤总有机碳及各级颗粒有机碳与外源有机碳的输入呈显著正线性相关关系,其中土壤总固碳效率为10.57%而各级颗粒之间,粘粒和砂粒组分的固碳效率（4.25%和3.60%）相当于粗粉粒和细粉粒（1.73%和1.00%）的2倍以上。【结论】南方红壤各级颗粒中有机碳均?

英文摘要：

[Objectives]Our objective was to explore effects of various long-term fertilization practices on soil organic carbon distribution ratios and quantitate the relationship between organic carbon sequestered and additional organic carbon input in different particle-size fractions.[Methods]The designed treatments were selected to obtain a gradient of additional carbon input,including no fertilizer control（CK）,chemical nitrogen,phosphorus and potassium fertilizers（NPK）,straw return with chemical fertilizers（NPKS）,chemical fertilizers combined with manure（NPKM）,chemical fertilizer combined with manure under soybean rotation（NPKMR）,manure（M）alone,and high application rate of NPKM（1.5NPKM）.Soil samples were collected after twenty-year fertilization practices,and separated into sand（53-2000μm）,coarse silt（5-53 μm）,fine silt（2-5 μm） and clay（2μm） by the physical fractionation.[Results]Compared with CK,the total soil organic carbon（SOC） stocks and those of the particle-size fractions are significantly increased under the fertilization treatments.The long-term application of manure with or without chemical fertilizers is the most effective practice for increasing soil organic carbon.The SOC stock in the clay fraction（16.26 t/hm2） is the highest among the four particle-size fractions after the 20 years fertilization treatments.The treatments with manure and straw incorporation significantly increase the SOC distribution proportion in the sand size fraction（13.33%- 25.36%）,while the treatments reduce the proportions in the clay-size fraction,and there are no significant changes in both the coarse and fine silt fractions.However,the application of chemical fertilizer has less effects on the organic carbon distribution ratios of the fractions.The concentrations of SOC in the coarse silt,fine silt,and clay size fractions are significantly correlated with the mass proportion of sand size fraction and the mass ratio of sand to coarse silt,fine silt,and clay size fractions,r