Effect of Long-term Straw Returning Field on the Carbon and Nitrogen in Black Soil and Maize Yield

Through long-term located experiment,the effect of long-term straw returning field on the carbon and nitrogen in black soil and maize yield were studied.The results showed that maize straw returning field could not promote the accumulation of organic carbon significantly,as compared with NPK treatment.But soil organic carbon increased a lot in three treatments,recent years of soil organic carbon compared with the initial one showed the significant difference.S+NPK treatment could improve the supplying level of soil N,compared to the treatments CK and NPK.The ratio of C and N ranged from 10.23 to 11.26.Maize average yield in 19 years was 8 958 kg/ha with S+NPK treatment,similarly to NPK treatment,significantly higher to CK treatment,which indicated that applying organic N(maize straw) take the place of parts of mineral N can reach the same level of maize yield completely.