Grazing-livestock system productivity of legume-grass mixtures in the Loess Plateau of China

Three mixture types, Medicago sativa + Dactylis glomerata, M. sativa + Festuca arundinacea, and M. sativa + Bromus inermis, were established on sunny and shady slope, respectively and used for cattle rotational grazing in the second year after the establishment. The pasture composition, nutritional quality, and pasture production of the three mixture types were determined. The live weight gain (LWG) of the cattle fed the various mixture types was also determined. The aim of this study was to evaluate the grass-livestock system productivity of different legume-grass mixtures on sunny and shady slopes of abandoned farmland in the Loess Plateau of China and provide a basis for the establishment and utilization of legume-grass mixtures in the area. The results showed that the dry weight proportion of the seeded species (M. sativa and perennial grass) in the sward was maintained at more than 80% in each mixture type. The net energy for growth and crude protein concentration of forage ranged from 1.6 to 3.0 MJ·kg⁻¹ and 12.7% to 17.6%, respectively. On each slope aspect, the pasture production of M. sativa + D. glomerata was significantly (P < 0.05) higher than that of the other two mixtures, and the pasture production on sunny slope was significantly (P < 0.05) higher than that on shady slope. The LWG per cattle did not differ significantly (P > 0.05) among the three mixture types. The forage in each mixture type on sunny slope could continuously meet the nutritional requirement of 450 kg cattle with a daily gain of more than 1.2 kg. The LWG per cattle on sunny slope was significantly (P < 0.05) higher than that on shady slope, possibly owing to more energy expenditure during cattle grazing on shady slope. LWG per hectare of cattle grazing on sunny slope depended on pasture production, and the LWG of M. sativa + D. glomerata was 11.4% and 18.4% higher than those of the other two mixtures, respectively. Based on the above analysis, pasture production and LWG per hectare of M. sativa + D. glomerata were the highest among the three mixture types and could be considered as the first choice in the establishment of legume-grass mixtures in this area. However, the pasture production on sunny slope was higher than that on shady slope; therefore, it is more suitable to establish grazing-type legume-grass mixtures on sunny slope to obtain more production benefits for the grass-livestock system.