Study on allelopathic effects of alfalfa / forage maize / sorghum-sudangrass hybrid

In this experiment, alfalfa (Medicago sativa), forage maize (Zea mays), and sorghum-sudangrass hybrid (Sorghum bicolor × S. sudanense) were used as receptor plants, and plant germination and seedling growth were measured at different concentrations (0, 12.5, 25, 50, 100, 150, 200 mg·mL⁻¹). The aim was to investigate the relationship between the three crops and their allelopathic effects, and to provide a reference for crop rotation, mixed cropping or intercropping production. The results showed that all three crops had allelopathic effects on each other, and the effects differed significantly depending on the receptor plant species, receptor organ and tissue extract concentration. In the range of concentrations tested, 25 and 50 mg·mL⁻¹ of forage maize aqueous extracts were the best concentrations to promote the growth of alfalfa and sorghum-sudangrass hybrid, respectively, and both had the best effect on seed vigor, with a synthetical effect (SE) of 0.074 and 0.092, respectively. A concentration of 50 mg·mL⁻¹ of alfalfa aqueous extract was the best concentration to promote the growth of forage maize (SE = 0.027), and the best effect to promote radicle growth; all concentrations of alfalfa aqueous extracts were inhibitory to sorghum-sudangrass hybrid (SE < 0), All concentrations of sorghum-sudangrass hybrid aqueous extracts were inhibitory to alfalfa and forage maize (SE < 0). In conclusion, alfalfa should be rotated, set or mixed with forage maize and not with sorghum-sudangrass hybrid, and forage maize can be used as the front crop of sorghum-sudangrass hybrid, but not as the back crop. In addition, when forage maize is the main harvesting object, set or mixed sowing is not suitable.