Green manure is a biological fertilizer source with complete nutrients, which provides reference for the selection of green manure resistant to low temperature germination. Six green manure crops including Brassica napus L., Orychophragmus violaceus (L.) O. E. Schulz, Medicago sativa L., Lolium perenne L., Melilotus officinalis (Linn.) Pall. and Vicia villosaRoth were selected as experimental materials to study the effects of low temperature stress on germination and seedling growth of different green manure through low temperature germination experiments. The results showed that there were significant differences in cold tolerance of the seeds of 6 medium green manure crops during germination. The germination potential, germination rate, germination index, vitality index, seedling height, root length, seedling fresh weight, soluble protein content and chlorophyll content of Brassica napus L. and Vicia villosaRoth seeds were all better than those of other green manure crops, which provided theoretical basis for the actual production of green manure.

In order to explore the response mechanism of heavy metal content in Oryza sativa L. fields under winter green manure. In this study, through field experiments, the changes of soil chemical properties and heavy metal content in Brassica napus L. and Oryza sativa L. at different growth stages were analyzed. The results are as follows: the pH value in Brassica napus L. harvest stage is higher than that before sowing, while the pH value in Oryza sativa L. harvest stage is lower than that before sowing. Eh of Brassica napus L. soil is positive during the whole growth period, showing a fluctuating upward trend. Eh of soil decreased to negative value during the whole growth period of Oryza sativa L. The contents of As, Hg, Pb, Cd and Cr in the soil decreased gradually in the whole growth period of Brassica napus L., and decreased to the lowest level in the harvest period. During the whole growth period of Oryza sativa L., the content of Hg and Cd decreased, while the content of Pb and Cr increased in the harvest period compared with before sowing. Therefore, planting green manure Brassica napus L. in winter is beneficial to alleviate heavy metal pollution in soil.