| In order to explore the effects of wheat rotation for reducing continuous cropping obstacle of oil flax，field experiments were conducted. The plant height and yield of oil flax were studied, and soil enzyme activity and the allelopathy of water extracts of soil were analyzed. The results showed that heavy stubble cultivation of oil flax caused the phenomenon of continuous cropping obstacle. Oil flax continuous cropping for three year showed that the plant height, the rate of emergence, the thousand grain weight and the per plant yield decreased by 14.0%, 7.75%, 33.8% and 43.2%, respectively. Wheat rotation eliminated continuous cropping obstacle, so that the plant height and yield remained at the level of first year, which was 69.7 cm and 1.43 g·plant-1, respectively. After wheat rotation, catalase, urease and alkaline phosphatase activities in the soil were 2.41 mL·g-1·h-1, 2.32 mg·g-1·d-1 and 9.04 mg·g-1·d-1, respectively. There was no significant difference between the soil enzyme activity in the soil of continuous cropping of oil flax for one year. Continuous cropping led to major changes in soil enzyme activity. The activity of soil catalase, urease and alkaline phosphatase decreased to 2.16 mL·g-1·h-1, 8.18 mg·g-1·d-1 and 2.01 mg·g-1·d-1 after continuous cropping of oil flax for two years. This indicated that wheat rotation reduced continuous cropping obstacle by maintaining soil enzyme activity, which was conducive to the growth of next stubble oil flax. Compared with continuous cropping of oil flax, rotation with wheat reduced the allelopathy autotoxicity of aqueous extracts from soil on seed germination and seedling growth of oil flax, and showed 0.21% synthesis effect that promoted action. The germination index (46.0), germination potential (92.0%), vitality index (3.36), root length (8.35 cm) and root weight (23.17 mg) were not significantly different from that of CK and TC1 conditions. Continuous cropping enhanced water extractable toxin in soil, which had a negative effect on the germination and seedling growth of oil flax. The synthesis effect was reduced to -8.61% and -17.01% with the increase of years of continuous cultivation, and the inhibition effects were enhanced. It was indicated that rotation of wheat could reduce the continuous cropping obstacle of oil flax by reducing the autotoxicity. In summary, heavy crop cultivation of oil flax led to obvious continuous cropping obstacle. Reasonable rotation with wheat helped to maintain the soil enzyme activity and reduce the autotoxicity of oil flax land, thus, reducing the occurrence of continuous cropping obstacle in oil flax. |