The Combination of Achnatherum inebrians Extracts and Soil Microorganisms Inhibited Seed Germination and Seedling Growth in Elymus nutans

In a greenhouse experiment, the effects of soil microorganisms and extracts of Achnatherum inebrians on the seed germination and seedling growth of Elymus nutans were studied. The results showed that both the extracts from aboveground and belowground parts of A. inebrians significantly inhibited the germination rate, germination potential, germination index, vigor index, seedling height, root length, and fresh weight of E. nutans, but increased malondialdehyde content, catalase, peroxidase and superoxide dismutase activity of E. nutans seedlings (p < 0.05). The allelopathy of aqueous extracts of the aboveground parts of A. inebrians was stronger than that of the precipitates. Aqueous extracts of the aboveground parts of A. inebrians decreased seed germination rate, germination potential, germination index, vigor index, seedling length, root length, and seedling fresh weight by 10.45%–74.63%, 24.18%–32.50%, 19.03%–73.36%, 37.83%–88.41%, 21.42%–53.14%, 2.65%–40.21%, and 20.45%–61.36%, respectively, and malondialdehyde content, peroxidase, catalase, and superoxide dismutase activity increased by 8.09%–62.24%, 27.83%–86.47%, 22.90%–93.17%, and 11.15%–75.91%, respectively. The above indexes were higher in live soil than in sterilized soil. Soil microorganisms increased the allelopathy of A. inebrians. The seed germination rate, germination potential, germination index, vigor index, seedling length, and seedling fresh weight of E. nutans planted in live soil decreased by 8.22%–48.48%, 10.00%–51.85%, 8.19%–53.26%, 16.43%–60.03%, 12.91%–28.81%, and 9.09%–22.86% compared with sterilized soil, respectively. Malondialdehyde content, peroxidase, catalase, and superoxide dismutase activity of E. nutans planted in live soil increased by 53.91%–81.06%, 15.71%–57.34%, 33.33%–86.31%, and 9.78%–52.51% compared with sterilized soil, respectively. The existence of soil microorganisms enhanced the allelopathy of the secondary metabolites of A. inebrians. A combination of microorganisms and aqueous extracts from the aboveground parts of A. inebrians had the strongest allelopathic effect on E. nutans.