Foxtail millet genotypic variation and legume species selection in enhancing grain quality and resource efficiency in a dryland intercropping system

To evaluate the impact of foxtail millet-legume intercropping on millet growth, yield, and grain quality, a field experiment was conducted using three foxtail millet (Setaria italica (L.) P.Beauv.) genotypes (cv. 'Dabaigu', 'Jizhanggu 5', and 'Jinmiao K1') intercropped with three legume species (red adzuki bean, mung bean, and red kidney bean) in a 1:1 row replacement design. The study assessed the responses of millet to intercropping across phenological stages. The highest land equivalent ratio (LER) was recorded for the Dabaigu/red adzuki bean combination, indicating superior resource-use efficiency. During the seedling and booting stages, sole cropping significantly increased plant height, flag leaf chlorophyll content, and dry weights of leaves, stems, and panicles compared with intercropping. At heading, intercropping improved single-leaf area and dry matter accumulation. By maturity, sole cropping showed a trend of increased panicle traits; however, intercropped millet exhibited significantly higher grain nutritional quality, including crude protein, crude fat, amylose content, and gelatinization viscosity. A significant negative correlation was observed between yield-related agronomic traits and grain quality parameters. These findings offer valuable insights into optimizing millet-legume intercropping systems for enhancing resource efficiency and nutritional value under dryland conditions in North China.