Soil organic matter is a heterogeneous material because of its different components and stability mechanisms,so the changes of soil organic carbon(SOC)and nitrogen(SON)fractions over time were different in their turnover rates.Therefore,physical fractionation procedure was adopted to study three fertilizer treatments,namely NPK(inorganic fertilizer),NPKS(inorganic fertilizer & straw)and NPKM(inorganic fertilizer & manure)on labile and recalcitrant organic C and N pool in black soil.The results showed SOC and TN contents under NPK and NPKS treatments changed little over past 23 years.While NPKM treatment significantly increased SOC and TN contents by 0.28 g/kg and 0.04 g/kg per year,respectively.NPKS and NPKM treatments significantly reduced the proportion of >150 μm MF fraction.NPKM treatment significantly increased the proportions of total C and N stored in the >150 μm MOM fraction.Comparing with NPK treatment,labile carbon pools under NPKS and NPKM treatments increased by 0.9 percent and 5.9 percent,respectively.Labile nitrogen pools increased 1.8 percent and 9.9 percent for NPKS and NPKM treatments,respectively.In all,NPKS and NPKM treatments improve SOC and SON amount and quality among fractions.And NPKM treatment was significantly better than NPKS treatment in improving quantity and quality of SOC and SON in different fractions.