Legume Integration Augments the Forage Productivity and Quality in Maize-Based System in the Loess Plateau Region

The changing climate, inadequate water supply, insufficient agricultural inputs, decreasing in agricultural arable land areas under forage crops of Northwestern Loess Plateau region, expanding livestock population, increasing demands for meat and milk production, and food and feed security concerns all insist on a necessary requirement in forage quality production. Cereal–legume mixed-cropping is a biological approach to enhancing herbage yield and quality of upgraded animal feed (forage and silage). However, little information exists about the appropriate mixing seeding ratios and its impacts on yield and quality. Therefore, this study was conducted to examine the forage yield and nutritional quality of maize ( Zea mays L.) and common bean ( Phaseolus vulgaris L.) in mono-and mixed-cropping approaches at the seeding proportions of 100:0, 75:25, 50:50, 45:55, 25:75, and 0:100 in 2019 and 2020 in Northwestern Loess Plateau region. A randomized complete block design with four replicates was used in this experiment. The results indicated that forage quality was significantly affected by the mixture ratios. The land equivalent ratio (LER) of all mixed-cropping treatments greater than 1.0, in which maize–common bean at the 50:50 seeding ratio achieved higher LER (1.46) than that of other treatments, showing that mixed-cropping combination systems are better users of land resources. Laboratory forage quality analysis and Pearson correlation analysis showed that the relative feed value had highly positive correlation with total digestible nutrients and relative forage quality in mixed-cropping treatments. Our results showed that fresh forage yield and dry matter yield were higher in monocropped maize forage than in other intercropped forages, whereas crude protein yield was lower compared with other mixed cropping forages. After 60 days of ensiling, the highest organic acid profile and ammonia-nitrogen were observed in M25:CB75 silage compared with other silages. The highest ensilability of fermentation coefficient was also found in M50:CB50 compared with other intercropped silages. Regarding forage preservation, silage showed higher contents of crude protein, relative feed value and lower crude fiber, water-soluble carbohydrate neutral detergent fiber, and acid detergent fiber contents than forage. This study determined that the ratios of maize–common bean 25:75 and 50:50 were the most desirable mixture ratios among mixed-cropped forage and silage based on chemical composition and quality analysis for livestock feeding.