Abstract: To study the effect of different tillage methods on the enzyme activity of the soil in the rape field,and to provide the theoretical basis for the selection and application of the rational cultivation method in Northern agro-pastoral ecotone,the study analyzed the no-tillage straw returning to the field （NT）,the rotary tillage straw returning to the field （RT）,the conventional plowing straw not in the field （T）,traditional ploughing straw returning field （TS）,and deep pine straw returning field （DT）.The effects of different tillage methods on the activity of the soil in different soil layers of the rape field before and after sowing were studied.The results showed that the different tillage methods have similar effect on the change of the activity of the soil profile.The activity of the surface soil enzyme is higher than that of the deep soil enzyme.There are some differences in the changing trend of the enzyme activity under different treatments.The activities of sucrase and urease were the highest in no-ploughing straw returning treatment,and the catalase activity was the highest in rotary ploughing straw returning treatment.There was no significant difference in the effect of different farming methods on soil alkaline phosphatase activity in 0-20 cm soil layer.The average soil catalase and sucrase activities in 0-60 cm soil layer were as follows：pre-sowing > post-harvest,while alkaline phosphatase activity was pre-sowing < post-harvest.Except for T treatment,TS treatment showed pre-sowing < and post-harvest,and the other three treatments showed pre-sowing > post-harvest.

Key words: Northern agro-pastoral ecotone, Rapeseed fields, Farming methods, Soil enzymes, Enzymatic activity