Abstract: A four year stationary field experiment was carried out on straw incorporation in Shajiang (lime concretion) black soil in Mengcheng, Anhui for exploration of variation of soil organic matter composition and carbon pool management index in the plow layer and analysis of relationships between organic matter composition, crop yield and carbon pool management index. Results show that straw incorporation significantly increased the contents of total soil organic matter and labile soil organic matter and carbon pool management index (P<0.05). Straw incorporation coupled with N fertilization (360～720 kg?hm^-2) increased the contents of total soil organic matter and labile soil organic matter and carbon pool management index in the top soil by 10.1%-15.8%、20.4%-32.5% and 41.7%-74.6%，respectively, as compared to straw incorporation alone. The treatment of straw incorporation coupled with N fertilization at a rate of 540 kg?hm^-2 was the highest in increment of labile soil organic matter and the increase occurred mainly in the fraction of inertia labile organic matter. Grain yield of maize was significantly related to total organic matter, labile organic matter and carbon management index ( P <0. 01 ). The above findings indicate that straw incorporation coupled with N fertilization improves quality of soil organic matter, and the effect is especially significant when N application rate is set at 540 kg?hm^-2 in Shajiang (lime concretion) black soil.

Key words: straw returning, Shajiang (lime concretion) black soil, soil organic matter, carbon pool management index