Faba Bean Extracts Allelopathically Inhibited Seed Germination and Promoted Seedling Growth of Maize

Allelopathic interactions between crops in an intercropping system can directly affect crop yields. Faba beans may release allelochemicals to the cropping system. However, the allelopathic effects in the faba bean–maize relay intercropping system are still unclear. Maize seeds and seedlings were treated with a 50 mL of 100 g L⁻¹ faba bean leaf extract (L1), 150 g L⁻¹ faba bean leaf extract (L2), 100 g L⁻¹ faba bean stem extract (S1), or 150 g L⁻¹ faba bean stem extract (S2) and sterile water (CK) to study the allelopathic effects of faba bean extracts on maize seed germination and seedling growth. The α-amylase activities, antioxidant enzyme activities, phytohormones and allelochemical content in maize seeds were determined to evaluate the allelopathic effects of faba bean extracts on maize seed germination. The agronomic traits, photosynthetic parameters and nutrient absorption characteristics of maize seedlings were determined to explore the allelopathic effects of faba bean extracts on maize seedling growth. High-concentration (150 g L⁻¹) faba bean stem extracts released allelochemicals, such as 4-hydroxybenzoic acid, hydrocinnamic acid, trans-cinnamic acid, and benzoic acid. These allelochemicals entered the interior of maize seeds and increased the abscisic acid, salicylic acid and indole-3-acetic acid content in maize seeds but decreased the aminocyclopropane carboxylic acid in maize seeds. High-concentration (150 g L⁻¹) faba bean stem extracts increased the superoxide dismutase and peroxidase activity and decreased the α-amylase activity in maize seeds at germination (36 h). Faba bean extracts released nitrogen, potassium and phosphorus and increased nitrogen content, phosphorus content, potassium content and photosynthesis of maize seedling. In summary, faba bean extracts released allelochemicals that inhibited the germination of maize seeds but released nutrients and promoted the growth and development of maize seedlings. The research results provide a basis for improving the Faba bean–maize relay strip intercropping.